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From: (GCHudson)
Subject: Re: Roton idea requiring no rotating seals
Date: 07 May 1998 04:52:28 GMT

I can only answer briefly: several of our patent claims relate to rotating the
tanks and rotors as a single unit, but I unfortunately can't elaborate.  Once
the patent issues this changes.  But unless I'm missing something, you cant
contra-rotate tanks and still get both propellants into the engines...

And a repetition of an earlier point: Roton is Bevin McKinney's original idea,
not mine.  Both he and I have our names on the application, however, since I
helped in some details and elaborations of the first concept.

Gary C.  Hudson, CEO
Rotary Rocket Company

From: Henry Spencer <>
Subject: Re: Roton Crew Accomodations and ISS Docking
Date: Thu, 7 May 1998 15:31:58 GMT

In article <>,
Robert Lynn  <> wrote:
>> As a matter of policy, Rotary will not take government contracts, so...
>I find this very hard to believe.  If I were a shareholder in a company
>that held such a policy I would be acting to change it, to be successful
>in business you take money off everyone who is prepared to give it to
>you, if a customer fronts up with money and it is legal then you do
>business regardless of who they are.

Maybe and maybe not.  Rotary are far from the only people doing this;
Hewlett-Packard historically had a similar policy (possibly still does,
I'm not sure).

The problem is that the government is not an ordinary customer, and
dealing with them may be more hassle than it's worth.  They're unreliable
(contracts may be cancelled at any time for their convenience, and they
won't pay cancellation penalties), they want mountains of paperwork, they
want extensive insight into your business (even on fixed-price contracts,
they want to know exactly how the money gets spent), they impose a lot of
troublesome constraints on how you do business, they tend to pay late, and
they demand your lowest price despite all these hassles.  Convincing them
to behave like an ordinary customer on a major contract is nearly
impossible unless you've got some sort of unique edge so that they've got
no choice but to do things your way, and even then it's a hassle (as Burt
Rutan can testify).

My understanding is that Rotary's current major investors not only agree
with this policy but strongly encouraged it.
Being the last man on the Moon                  |     Henry Spencer
is a very dubious honor. -- Gene Cernan         |

From: (GCHudson)
Subject: Re: Len's Bantam X: why not HTHL?
Date: 24 May 1998 06:31:45 GMT

Jim Davis wrote:

>Hudson's Roton illustrates the point well. Hudson is trying to introduce
three revolutionary technologies into one vehicle in one step - the
telescoping rotor recovery device, the centrifugal fed rocket engine,
and the light weight structure required to acheive SSTO. History tells
that introducing one revolutionary technology is very risky.

Beyond this Hudson is gambling that there will be enough of a market for
the Roton right from the start. To be profitable a commercial airliner
has to be earning revenue 18-20 hours a day. I don't know the numbers
for Roton but I think it'll have to be on the order of 100 flights a
year to seriously undercut the existing launch vehicles and offer a
reasonable return on investment. Hudson might try to lowball to buy
market share but his competitors can play that game longer than he can.<

Hasty response:  there are not three new technologies in the Roton which are
unproven.  The rotor system has been demonstrated in drop tests and wind tunnel
runs (and I wouldn't believe everything you see on our web site relating to the
rotor...).  Mass fraction adequate to reach orbit has already been demonstrated
in many other vehicles, too numerous to more than mention here (S-IVB, Titan,
HAVE REGION efforts, etc.).  Centrifugal pumping on the scale of the Roton is
new but has been demonstrated in smaller engines and of course is grounded in
simple physics.  But I admit the collection of technologies is challenging.
That's why the reward is so high: the risk must be accepted to achieve the

I would quibble with the last point, however, which is that other competitors
can lowball Rotary.  It's pretty hard to compete with an airline which reuses
its aircraft when you throw them away after each flight.  And it doesn't take
anywhere near 100 flights per year for us to be profitable, not competing
against expendables.

Finally, while I am CEO of Rotary, the Roton is not my invention,  but that of
my colleague, Bevin McKinney, our CTO.

Gary C. Hudson, CEO
Rotary Rocket Company

From: (GCHudson)
Subject: Re: Roton Reservations (was Re: Len's Bantam X: why not HTHL?)
Date: 25 May 1998 16:18:45 GMT

Jim Davis wrote:

>...Mr. Hudson, I truly hope that you are to the 21st century what the
Wrights were to the 20th. I just can't bring myself to accept your
technical and commercial success as a foregone conclusion as others on
this newsgroup have.<

I regret not having time to reply properly to a thoughtful post, but will just
say that *I* don't regard our technical and commercial success as a foregone
conclusion!  The technical challenges are significant, but we are making good
progress towards meeting each. (A quick comment about resuable structures: the
HAVE REGION hardware was resuable, not expendable, and achieved mass fraction
goals for a hydrogen SSTO.  We're doing kerosene, and our system is being built
right now.  It will meet the mass goals set for it, and we've already
demonstrated most of the life-cycle gaols, such as 100+ thermal cycles on main
tank elements.)  I would disagree that  commercial success will be a major
issue if we meet the technical challenges; everything depends on development
costs.  If, as we belive and have proven to our investor's satisfaction, that
the development cost of our reusable is equal to or less than an expenable of
the same payload performance, then commercial success *is* virtually assured.

Gary C. Hudson, CEO
Rotary Rocket Company

From: (GCHudson)
Subject: Re: Roton Reservations (was Re: Len's Bantam X: why not HTHL?)M
Date: 26 May 1998 15:08:22 GMT

Marcus wrote:

>> wrote:
: In article <>,
: wrote:
: > > Mass fraction adequate to reach orbit has already been demonstrated
: > > in many other vehicles, too numerous to more than mention here (S-IVB,
: > > Titan,
: > > HAVE REGION efforts, etc.).
: >
: > But you will have to push the structural state of the art far beyond
: > these *expendable* examples in order for your *reusable* vehicle to have
: > much better performance.
: How are you so sure? If a S-IV is an adequate SSTO expendable,

It's would need twice as many engines to achieve a decent
liftoff thrust. Now, I agree that modern technology certainly makes
SSTOs feasible, but the S-IV wasn't it.<<

Actually, all it requires is replacing the J-2 with an SSME.  The interface
structure can handle the thrust loads, and the stage can then place about 10K
pounds over its own empty mass to about 30K fps.  So the S-IVB is a perfectly
viable expendable SSTO, right out of the box.  In addition, I've never
accounted for deletion of the aft interstage (about 1200 lbs mass) or rework of
the forward one to composites.  So there is margin to spare.  A further note:
if you try and do this calculation yourself, make sure you don't make the
mistake of including the mass of the Saturn IU as part of the S-IVB stage mass
(this is a common error).  That 4000 pounds of IU can be simply replaced by
about 150 ponds of "pegasus style" avionics, today.

Gary C. Hudson

From: (GCHudson)
Subject: Re: Roton Reservations
Date: 11 Jun 1998 04:33:48 GMT

frankzeg wrote:

>I share the interest in how this design problem will be addressed.  I guess I
fail to see how you can avoid having to deal with a LO2 compatible seal
somewhere in this gizmo.  You can direct the leakage away that is clear but
there has to be a primary barrier somewhere.  Gotta be careful about
introducing non-condensible gases into the LO2 flowstream too. Recognize that
several of the best seal materials wiht long life and good cryogenic
properties are denied you in lO2 service- spcifically UHMW polyethylene is
not LO2 compatible for impact. So you will be essentially forced to the
Teflons or Kel-F which are not quite so long lived.  The good thing is that
the wear is reduced at the cold temps.	I'm sure that Furon, Polymer Concepts
or Tetrafluor will be well employed by these guys for some time.<

The issue is psia x rpm, which is the figure of merit used to evaluate seal
risk.  By this figure of merit, our seals are an order of magnitude less risky
than standard rocket turbopump seals for LOX, many of which seal not simply to
the outer world, but between LOX and warm fuel rich gases.

Gary C. Hudson

From: (Henry Spencer)
Subject: Re: Roton Reservations
Date: Mon, 15 Jun 1998 21:30:05 GMT

In article <6lvk6q$g49$>,  <> wrote:
>...I concurr that there are pump seals
>that already deal with sealing HP LO2 at very high RPM's but I guess my
>experience is that these are pretty life least for the ROTON
>application....but perhaps at your reduced loads they'll be OK

Not that life-limited -- the RL10 is rated for over an hour of firing
(assuming you can somehow supply it with enough LOX/LH2), either
continuous or in several burns, and that's probably conservative.

>Henry I'd be very interested in any resources you could direct me to on the
>impact test being over-conservative.

Gary Hudson. :-)  What he's said at the last two Space Access conferences
has been roughly:

  "They told me that graphite-epoxy ignites about 70% of the time on
  the impact test.  So I asked them about 6061T6 aluminum.  They said that
  it ignites about 30% of the time.  I asked them how it could ever have
  been cleared for LOX compatibility.  They said they wrote a waiver for
  it!  So we've been doing our own experimenting -- filling and draining
  Gr-Ep LOX tanks repeatedly, pressurizing them, overpressurizing them,
  bursting them, bursting them with deliberate flaws in them...  Not once
  have we seen an explosion or an ignition.  I'm starting to be tempted
  to put an incendiary bullet into one of them to see if *that* will make
  it ignite."

The word is spreading.  I'm starting to see references to unlined composite
LOX tanks in other people's project plans too.
Being the last man on the Moon is a |  Henry Spencer
very dubious honor. -- Gene Cernan  |      (aka

From: Doug Jones <>
Subject: Re: Roton design questions
Date: 18 Jun 1998
Newsgroups:, wrote:
> I have a number of questions about the Roton design. Any authoritative
> information or informed speculation will be appreciated.

I am a propulsion engineer with Rotary, so I will answer your questions
where I can, within proprietary limits.

> 1.) The Rotory Rocket web page says that Roton will use ordinary jet
> fuel, presumably the commercial grade Jet A. Does this mean that the
> Roton thrust chambers are oxidizer cooled since Jet A is not a
> suitable coolant? Or is "ordinary jet fuel" merely a careless
> description of a rocket grade propellant like RP-1?

Yes, oxidizer cooled for several reasons- Jet A is a lousy coolant, we
have 2.9x the mass of LOX as of fuel available for cooling, and (most
important), the LOX has more pressure available for cooling.  Bear in
mind that flowing through the coolant passages requires a substantial
pressure drop, and since the LOX is denser than the fuel, it reaches
higher pressure in the centrifugal pumping of the wheel.  Thus it is the
logical choice for coolant- and it does not foul, no how no way.

> 2.) If Roton is intended to use Jet A what is the reason? Is the
> higher cost or lesser availability of RP-1 really that significant?
> I understand that a preburner is being used to vaporize the fuel.
> Are the advantages of Jet A really worth such a complication?

Availability is the key concern- Jet A and LOX are readily available
right here in Mojave (or any othe airfield), while RP-1 is a pain and
gives no improvement in performance.  With LOX cooling, there is no need
for low-fouling RP-1 (as Bruce Dunn has pointed out, RP-1 is much like
odorless high-quality lamp oil, though a bit more volatile).

> 3.) The Rotary Rocket web page gives the gross liftoff weight of the
> Roton as 150,000 kg and the fuel weight as 23,000 kg. The oxidizer is
> stated to be liquid oxygen. This would mean the mixture ratio
> averages out to be about 5 to 1. This is well above stoichiometric
> for liquid oxygen. Is Roton planned with a variable mixture ratio -
> oxidizer rich for take off gradually changing to fuel rich during
> ascent? Would the rotary engine design be consistent with variable
> mixture ratio operation? Could Rotary Rocket be pulling a fast one
> and be using hydrogen peroxide as the oxidizer?

Nope- the folks who put together the web page aren't in the same city as
us grunts doing the design.  Since I'm working on the engines
themselves, I haven't kept abreast of the overall vehicle mass (I have a
reference on my desk at work, but I haven't looked at those numbers in
detail).  We are looking at a mixture ratio of about 2.9, since the Isp
is only a bit lower than at 2.4 while the density is a bit better.  No
fast ones- LOX is the only way to go.  We will have HTP tip thrusters on
the rotor so that we don't have to autorotate to landing, but main
propulsion will be LOX/JP.

> 4.) Does the Roton employ an aerospike or plug nozzle configuration?
> If a plug nozzle, does the plug rotate with the engine or is it
> fixed? If an aerospike, where does the exhaust that forms the
> "spike" come from since there are no turbopump exhausts? From the
> fuel preburners?

Sorry, that's something I may not talk about- details are proprietary:
"I will neither confirm nor deny..."

> 5.) If the Roton does use a plug nozzle engine is the plug occupied
> by any propellant tanks? In other words does the rotary engine
> separate the Roton into two parts - the upper carrying the oxidizer
> and the lower carrying the fuel? Or does the rotating assembly form
> the entire aft end of the Roton?

The latter- the wheel is the base, and includes the reentry heat shield.

> 6.) How are pitch and roll control effected during ascent? Does the
> Roton use a form of cyclic pitch in analogy to the helicopter with
> propellant flow in place of blade pitch? Or is the on orbit
> propulsion system used during ascent for control inputs?

Pitch and roll are proprietary- yaw about the long axis is controlled
with the RCS thrusters (wheel bearing drag makeup).  We may arrange the
RCS thrusters in "X" patterns instead of "+" patterns so that the yaw
RCS firings can have a 70% propulsion component.  The resolution of
manoeuvers into RCS firings is a programming exercise in matrix
algebra...  Nomenclature is a bit of a problem, since the long, vertical
axis is typically termed the roll axis on expendable launchers-- but our
pilot is sitting up, facing forward out of the side of the vehicle. From
his point of view, the long axis is yaw, and the others are pitch and
roll.  Ah, confusion...

I really want the left seat (right seat is commander's seat in
rotorcraft), but I'm afraid there's several guys both senior to me and
better qualified.  Shoot.

Sorry to leave you hanging on some points, but it's the old dilemma of,
"Them that knows, don't talk, them that talks, don't know."

Doug Jones
(Not speaking officially for RRC)

From: "Gary C. Hudson" <>
Subject: Re: ROTON and G-Limiting
Date: Mon, 27 Jul 1998 17:25:53 -0700 wrote:

> It's hard to believe they plan on subjecting the crew to several minutes of
> high-g loads in this position.  It would be the same as making a
> several-minute-long high-g turn in a fighter plane.  Maybe there's some more
> disinformation involved here?  Maybe the 8-g reentry load is an emergency
> maximum, and normal loads are much lower?

The crew reclines during the ballistic entry portion of the flight.
Typical felt g during this portion peaks at about 7.5, but is above 4
for only a couple of minutes.  Our experience in the centrifuge suggest
this will not be a problem for any typical flight crew, especially since
they are not called upon to do anything involving exertion this time.

Gary C. Hudson, CEO
Rotary Rocket Company

From: (Henry Spencer)
Subject: Re: lockheed admits needing govt $$$ for venturestar
Date: Thu, 25 Feb 1999 15:49:59 GMT

In article <7b3cqh$jft$>,
 <> wrote:
>Somehow, I don't think this will make much of a difference vs. VTVL...
>We are, after all, talking about REUSABLE LAUNCHERS here -- *not* aircraft.
>Aircraft may perform hundreds or thousands of flight tests before
>becoming operational, but I don't think ROTON will fly to orbit a hundred
>times before they start offering commercial rides.

In his Roton talk at Space Access 96, Gary said "200 test flights, the
last 20 orbital".  I haven't heard more recent numbers, but historically
Gary has consistently preferred flight testing over paper analysis.

Yes, we are talking about reusable launchers... which need to be a lot
more like aircraft than like today's expendables.  They *should* fly to
orbit a hundred times before they start offering commercial rides (or
at least, full-price commercial rides).
The good old days                   |  Henry Spencer
weren't.                            |      (aka

From: (GCHudson)
Subject: Re: YARQ (yet another Roton question)
Date: 10 Mar 1999 00:45:36 GMT

>It seems necessary to provide some form of active control to maintain proper
>rotor speed.

Actually, early on we found the rotary engine is highly stable (and that is
part of the patent so I can't go into details, but leave it as an exercise for
the student...).  There is a slight rpm increase with increasing Isp, but that
can be handled by a number of tricks.  But for any given Isp and rpm, the
engine is stable.

Gary C. Hudson, CEO
Rotary Rocket Company

From: (GCHudson)
Subject: Re: Roton ATV blades
Date: 13 Mar 1999 06:03:38 GMT

Jim Davis wrote:

>The problem with Roton's RocketJet engine is that it is susceptible to a
single point failure.

The only single point failure is failure of the main thrust or moment bearings.
 We could double these up, but they have the same sort of MTBF to be expected
of an industrial bearing of their type, which is spectacularly high.  Further,
the bearing is monitored carefully between flights and it's spin down time is
measured, which is a highly accurate predictor of imminent bearing failure.

Gary C. Hudson, CEO
Rotary Rocket Company

From: (GCHudson)
Subject: Re: Odds on Roton?
Date: 13 Mar 1999 06:14:01 GMT

Jim Davis wrote:

>Certainly not. I would expect some logical progression in capabilities
>though. The structural efficiency of the Roton seems more like a quantum

Actually, working from memory, the Long Tank Thor has about the same propellant
mass fraction of the Roton.  Or thinking about this another way, if the S-IVB
was filled with lox-kerosene, its propellant mass fraction would be 0.968.
While the S-IVB with an SSME could inject about 10,000 pounds more than the
stage weight (as an SSTO ELV), using hydrocarbon fuel it will inject more than
20,000 pounds excess.  Given that the stage masses 22,300 pounds with the J-2
(and I have corrected for engine masses and t/w in the above calculations), it
is not a great leap of engineering to figure you might be able to recover a
similar sized vehicle for less than the empty mass of the expendable stage.

Gary C. Hudson, CEO
Rotary Rocket Company

From: (GCHudson)
Subject: Re: Odds on Roton?
Date: 13 Mar 1999 15:22:36 GMT

Jim Davis wrote:

>1. The S-IVB had a common bulkhead between propellant tanks. The Roton
>eliminates this and inserts an intertank structure, traditionally heavy

The common blkd was double walled, with nomex core, and was so overdesigned
that it did not invert with 2x MEOP applied.

>2. The S-IVB had the heavier propellant (LO2) located aft, also a
>feature of Thor, but not Atlas. Roton has the heavier propellant located
>forward which puts more load on the intertank structure.

We've found this doesn't much matter as the structure is sized by other loads,
including wind on pad and max q alpha.  And the density of kerosene and loax
are not so different.

>3. The S-IVB propellant tanks had efficient shapes (sphere, cylinder
>with hemispherical ends) while Roton has more complex shapes (frustum of
>cone with hemispherical ends, ellipsoid of revolution).

The internal pressure of the S-IVB was about 40 psi; Thor was 80-100 psi (with
dished and flanged blkds).  Our internal prssure is on the order of 20 psi;
makes a big difference.

Regret lack of time prevents more complete discussion.

Gary C. Hudson, CEO
Rotary Rocket Company

Date: Sat, 13 Mar 1999 13:22:19 -0800
From: Doug Jones <>
Subject: Re: Roton and the Rocket Eqn

Tim Johnson wrote:
> I assumed that Roton will need to
> produce 9100 m/s delta-v (ideal), that
> it will carry a 7000 lb payload, and
> that it will weigh 400,000 lbs loaded.
> I also assumed Isp=305 sec.  The
> rocket equation gave:

We expect to achieve vacuum Isp of 350 seconds, a bit less than
the best russian hydrocarbon engines demonstrated thirty years ago.
This drops the mass ratio dramatically, and dense vehicles don't need
quite so much delta-V.  We *do* have POST, and we use it.

Doug Jones, Rocket Plumber
Rotary Rocket Company

Subject: Re: Roton and the Rocket Eqn
Date: Sat, 13 Mar 1999 22:56:58 GMT

In article <>, wrote:
> I'm a bit skeptical.  My math
> (see below) tells me that Roton
> must weigh only 12,000 lbs empty.
> Is this really possible?

Your assumptions are a bit off, fortunately.

> I assumed that Roton will need to
> produce 9100 m/s delta-v (ideal), that

That's a shade high for a hydrocarbon-fueled
vehicle, since gravity and drag losses are lower
than for hydrogen-fueled vehicles.

> it will carry a 7000 lb payload, and
> that it will weigh 400,000 lbs loaded.
> I also assumed Isp=305 sec.

That Isp is *way* off.  In a single stage to
orbit vehicle, you spend much more of the trajectory
in vacuum than you do in the atmosphere, so vacuum
Isp matters most.  Besides which, "Ideal Delta-V"
includes back pressure losses, so it goes with
purely vacuum Isp.

Vacuum Isp for some existing LOX kerosene engines:
(my copy of Isakowitz is at work, so these are
 from Mark Wade's page at )

RD-58M (11D58M): 353 seconds
RD-120 (11D123): 350 seconds
RD-170 (11D520): 337 seconds
RS-27C (Delta Stg. 1): 302 seconds

Try it again using a tad lower delta-V and state
of the art vacuum Isp and you should see much
more reasonable mass fraction requirements.

Of course, many of the existing engines have other
drawbacks for SSTO use; but they show you what you
could attain given a suitable engine.

send replies to:                            Jeff Greason
  greason "at" ix dot netcom dot com        Propulsion Manager
                                            Rotary Rocket Company

Date: Sun, 14 Mar 1999 21:38:01 -0800
From: Doug Jones <>
Subject: Re: Roton and the Rocket Eqn

Phil Fraering wrote:

> >RD-58M (11D58M): 353 seconds
> >RD-120 (11D123): 350 seconds
> >RD-170 (11D520): 337 seconds
> >RS-27C (Delta Stg. 1): 302 seconds
> The last engine probably has a cut-down nozzle for
> working in the lower atmosphere, and could have a
> higher vaccum ISP with a different one, right?

Yes, the RS-27C has only a 12:1 expansion area ratio, but at 705 psi
Pc and very low 2.25 O:F ratio, there's not much that can be done with
a larger nozzle to improve it.

Doug Jones, Rocket Plumber
Rotary Rocket Company

Date: Mon, 19 Apr 1999 08:44:26 -0700
From: Doug Jones <>
Subject: Re: Roton Video Gallery and New Report

James Hollingshead wrote:

> What happens if you just leave the engine spinning after it is shut
> off. That way you don't need a brake of any sort, and you shouldn't
> get too much heat buildup at the hub (I'm assuming the friction of the
> bearing is relatively low here - somone correct me if I'm completely
> wrong).

To keep the bearing system stiff (thrust bearing plus moment bearing),
a fairly large preload is needed between the two.  This puts a minimum
floor on the power dissipated by the bearings, and they would overheat
if run dry.  We stop the wheel ASAP after the main engine burn.

Doug Jones, Rocket Plumber
Rotary Rocket Company

Date: Mon, 19 Apr 1999 18:30:35 -0700
From: Doug Jones <>
Subject: Re: Roton Video Gallery and New Report

Richard A. Schumacher wrote:
> "Run dry".  Hmm.  Are the bearings lubricated by the fuel?

I'm afraid we're getting into areas where I'm not sure how much we've
made public.  We have good answers to this and other questions, but
it's not my place to disseminate them.  If it's any consolation, I
find it rather frustrating, too- here I am working on this great
project and I can't *brag* about it!

I know that some of the details were freely discussed at the ATV
rollout, but I don't trust my memory for which ones weren't.

Doug Jones, Rocket Plumber
Rotary Rocket Company

From: (Henry Spencer)
Subject: Re: Roton and Fastrac
Date: Wed, 30 Jun 1999 17:49:46 GMT

In article <>,
James A Davis  <> wrote:
>1. The RocketJet engine was intended to operate at a mixture ratio of
>2.9:1. Does anyone know the mixture ratio of Fastrac? Since the Roton
>propellant tanks were presumably designed for a mixture ratio of 2.9...

Engines are seldom too fussy about the *exact* mixture ratio fed to them.
It's quite likely that a Fastrac derivative (which is what Rotary is
planning) would have no problem running on whatever mixture ratio is
convenient for the existing tankage.

>2. Fastrac has a chamber pressure of 632 psi and an expansion ratio of
>40:1. This indicates that it was intended for altitude use only; its Isp
>will be below 200s at sea level. This will be useless for Rotary's
>application. Yet if they truncate the nozzles for sea level Isp the
>vacuum Isp will fall below 300 s. How does Rotary get around this?

There are any number of ways to tackle this.  A good bet, knowing Gary's
past preferences, would be shortened nozzles on the engines themselves,
plus an aerospike arrangement to get a larger expansion ratio at altitude.
But there are plenty of ways to do altitude-compensating nozzles, and Gary
knows all of them, so it could be something else.  The one thing I'd bet
money on is that he's not going for a plain conventional fixed-expansion
nozzle, of any length.

>...If the Fastrac
>turbomachinery is coupled with the Rotary thrust chambers the LO2 flow
>will drop considerably because of the greater pressure drop. The mixture
>ratio will be lowered which will in turn lower Isp.

There are any number of ways of dealing with that, from modifications
to the turbomachinery to simply adding some extra pressure drop in the
fuel side of the plumbing.

>4. Rotary had intended to use widely available Jet A as fuel; Fastrac
>was designed with RP-1 as the fuel. Can the Fastrac gas generator and
>turbopump operate on Jet A? Will Rotary be forced to use RP-1?

Within reasonably normal density ranges, pumps don't much care what they
pump, so there's no problem on the pump side.  Coking in the gas generator
and turbine might perhaps be an issue.  The big reason for using RP-1 is
to do fuel cooling without polymerization in the cooling passages, which
isn't an issue if you aren't using the fuel for cooling.

>6. How can the layoff of the propulsion personnel be reconciled with the
>change in engine? Use of an off the shelf engine merely changes the
>problem from one of development to one of integration. The integration
>problem will presumably take much less time but will still require
>personnel with propulsion expertise.

There is still propulsion expertise within the company -- Gary and Bevin
if nobody else!  However, it might be that some of the issues involved are
being postponed, on the grounds that the new approach involves fewer
uncertainties there.  (Investors tend to like seeing major uncertainties
resolved early, even if that isn't the most logical sequence of
development.)  I don't have any inside info.
The good old days                   |  Henry Spencer
weren't.                            |      (aka

From: (Henry Spencer)
Subject: Re: Independent Space Firms' Stock Options?
Date: Thu, 1 Jul 1999 19:38:17 GMT

In article <>,
David E. Powell <> wrote:
>Do any Independent Space Firms (Rotaryt Rocket, Kistler Aerospace, etc.)
>have stock available on a publicly traded basis?

In general, no.  SEC regulations make it quite difficult for such
high-risk ventures to offer stock to the public, on the theory that the
"widows and orphans" don't have the necessary expertise to assess the
degree of risk involved.
The good old days                   |  Henry Spencer
weren't.                            |      (aka

From: (Henry Spencer)
Subject: Re: Roton Performance Risks... Roton is Dead!
Date: Fri, 2 Jul 1999 00:50:25 GMT

In article <>,
Jon S. Berndt <> wrote:
>> ...The blades and rotor bearing are about the only
>> really vital items... and that's true of any helicopter.
>But, how many helicopters have their blades pass through hypersonic
>flight perpendicular to the line of flight with the associated heating?

Not that big a deal, since the blades are inside the main shock and see
a relatively mild heating environment.  (This is why some older drawings
showed the blades coned up somewhat -- to keep them inside the shock --
although later work permitted shortening the blades and eliminated the
need for the coning.)  People have run rotors in hypersonic wind tunnels;
they were seriously examined as a spacecraft braking/landing system in
the 1960s.
The good old days                   |  Henry Spencer
weren't.                            |      (aka

From: Jeff Greason <>
Subject: Re: Roton Performance Risks... Roton is Dead!
Date: Fri, 02 Jul 1999 09:50:57 -0700

Pat wrote:

> Rand Simberg wrote:
> > method (parachutes) that was well tested in Apollo.  I now understand

> > that you are asking why Apollo didn't use rotor recovery.  George is
> > probably correct (and it might be verifiable by digging through
> > historical documents of the trades) that it was considered too high
> > risk for a crash program, and chutes were adequate.
> Len Cormier who often posts here, actually did some of this analysis
> when he was at North American.
> I think there were several issues to consider, including risk, weight,
> hypersonic flow issues, reliability.
> Apollo was driven for massive weight reductions, remember towards the
> end they were counting bandaids in the LEM, while at the same time
> driven to safety, with cost as no object.

Certainly a parachute becomes less risky when there is no
upper bound on the number of man-hours you take to inspect
it and make sure it is *exactly* right!

Operating within the bounds of non-disclosure, I'd like to
bring up another point here.  Recall that Apollo was a much
higher ballistic coefficient entry than any returning SSTO
or near-SSTO can be -- it's quite heavy for it's size.
The area of the rotor disk scales with the landed weight.
When you look at the scaling, you find that the Apollo rotor
blades extended through the entry shock -- this results in
*very* high heating rates in the region of shock impingement.

In a vehicle such as that described on Rotary's web site,
the rotor blade is much smaller compared to the vehicle base,
and much further back, which makes it pretty straightforward
to keep the blade inside the entry shock.

I believe the heating rates on the blades in the shock
impingement region were one of the major factors which led
to rotors being dropped for Apollo.  The vehicle described
on Rotary's web site can avoid that problem altogether.

Contact me at:                        Jeff Greason
   jgreason at hughes dot net         ex-Propulsion Manager
                                      ex-Rotary Rocket

From: (GCHudson)
Subject: Re: Roton Going Down The Shuttle Path?
Date: 04 Jul 1999 22:58:58 GMT

Mike walsh wrote:


>It was also meant to remind people that Rotary Rocket is
>planning to use a rocket engine developed by that
>"Great Satan" of some space actitivists, NASA.

We use a lot of technology developed by NASA.  But we also use a lot developed
by military contractors and we actually use a lot developed by the Soviets (and
a bit based on NAZI-funded rocket R&D, as well).  I don't really see that this
matters.  What we do not do is solicit or accept NASA funding for our
development.  The difference should be obvious to most people: in the former
cases, the information is there, in the public domain.  Anyone can use it.  In
the latter case, the taxpayer is paying Rotary to become a commercial success.
That is the job and the duty of our investors.

The Fastrac story is similar.  Technology was developed or refined by the NASA
team, and industry vendors made it work.  We can now go to those vendors and
buy things.  We can ask them to improve their products.  We did not ask NASA to
develop this technology for us, but since it is available to all comers, then
we have a duty to our investors to use it if it helps us get to first flight
faster or cheaper.

Gary C. Hudson, CEO
Rotary Rocket Company

From: (GCHudson)
Subject: Re: Space Access Web Site
Date: 03 Sep 1999 02:12:19 GMT

>You're missing thousands of small investors and the millions they could
>pump into Rotary Rocket Company.  Any plans to go public anytime soon?
>In the FAQs section of your web site, you are collecting names of those
>who would like to buy shares someday by having them contact
>  You state that Rotary Rocket is a private
>company "at present," and that those sending in their names will be
>contacted "when appropriate," not "if," which sounds like going public
>someday is a given.  Has this list of names grown enough to encourage
>you in your plans to going public, or is it a nonfactor?  What else are
>you waiting for- or what else will it take- to convince you that the
>timing is finally right for a public offering?  Undoubtedly you have a
>timetable, probably based on certain things first falling into place....

Securities law currently makes it too difficult to do what you suggest.  If we
ever consider an IPO, it would most likely be after successful test flights
into space.

Gary C. Hudson, CEO
Rotary Rocket Company

From: (GCHudson)
Subject: Re: New Rotary Rocket Graphics? (Mr. Hudson?)
Date: 08 Sep 1999 00:36:47 GMT

>BTW after seeing the video, I'm confused by negative characterizations
>of the ATV's handling.  Looked pretty good to me, especially given the
>novel configuration.

It is quite true that the vehicle is a handful to fly, but that is largely due
to our early decision not to use fly-by-wire for cyclic control (we do use it
for throttle) and not to incorporate an autothrottle. The latter decision was
based on simulations, but flight experience has shown it to be handy to reduce
pilot workload, and has now been build and is being tested.  The use of control
cables instead of fly-by-wire saved a fair amount of development time at the
trade of making the vehicle hard on the pilots.  An orbital version would be
fly-by-wire of necessity.  Finally, the very tall profile exagerates "wobbly"
motions which are common in all helos; watch any helicopter fly and then
imagine a fifty foot tall boom attached to the top of the rotor, and imagine
its motions.  All in all, I agree with you that we've done OK.  But we can
always do better.  ;)

Gary C. Hudson, CEO
Rotary Rocket Company

Date: Tue, 21 Sep 1999 10:55:00 -0700
From: Doug Jones <>
Subject: Re: Roton 2nd Flight wrote:
> There is a nice photo taken during the Roton ATV second flight on the
> Rotary Rocket website, but no accompanying press release.
> Anybody want to comment on how the flight went?

(All the following is based only on my own observations and speculation.)

I was rather pleased to see that the ATV flew much more stably than on the
first flight- probably due to more practice and a reduced workload. (I
heard through the grapevine that an autothrottle had been implemented, so
that the pilots didn't have to play chase-the-RPM- gauge.)

The thrusters lit off, the rotor fairly quickly came up to speed, then the
crew exercised the rotor speed control while at zero collective. At one
point the thrusters shut down altogether when they commanded lower speed,
then relit after the speed decayed.

After close to three minutes of diagnostics, they raised RPM, pulled
collective, and lifted off.  The yaw thrusters appeared to be on full,
giving more control authority.  Pitch and roll excursions were much less
than on the July 23 test, and the hover was sustained for two minutes. Yaw
tracking was also much better.  They kept the hover in a box about five
feet high by thirty feet wide (I couldn't see depth well enough to see fore
and aft travel, but I believe it was comparable to sideways motion).  Hover
altitude was around 10 +- 3 feet.

I hear that next month, after cooking up more peroxide, they plan to fly in
translational lift for some distance along the runway.

Congratulations, Rotary.

Doug Jones, Rocket Plumber

From: (GCHudson)
Subject: Re: Roton 2nd Flight
Date: 21 Sep 1999 22:15:16 GMT

>There is a nice photo taken during the Roton ATV second flight on the
>Rotary Rocket website, but no accompanying press release.
>Anybody want to comment on how the flight went?

It exceeded our expectations for a second test flight.  A press release should
be out by now. Altitude was about 15-20 for most of the hover and the pilot
took it up to 30 ft for some photograhic purposes.  Hover time was 2 min 15
second by my watch.

The vehicle behaved pretty much as the simulator suggested.  The autothrottle
worked very well (especially since it was implemented in about five weeks) and
the crew workload is now more normal for a heavy helo.  Basically, the vehicle
performs as we said it would at this point in the flight test program.

Gary C. Hudson, CEO
Rotary Rocket Company

From: (GCHudson)
Subject: Re: Gov't support of private RLV development
Date: 16 Oct 1999 18:34:12 GMT


>I'm sure they'd be more than happy to sell Rotons to NASA.

Yes, we'd sell them flights and vehicles.  We don't want development contracts,

We work pretty well with NASA these days.  Times have changed somewhat and they
are making progress with respect to the emerging launch firms.  Long way yet to
go, but long journeys still begin with small steps, etc.  Or short duration

Gary C. Hudson, CEO
Rotary Rocket Company

From: (GCHudson)
Subject: Re: Gov't support of private RLV development
Date: 17 Oct 1999 01:42:48 GMT

Kwright wrote:


>I see many potential  problems with tax incentives. As with so many
>things, the devil is in the details. This was not a hearing on any
>particular bill. Has any tax incentive bill been introduced ?

Orbital Sciences exists because of tax credits.  They raised $50 million in
1983 through the R&D Limited Partnership scheme, whcih was subsequently
eliminated in the tax reform bill in 1986.  They would have never raised those
funds without the tax benefit.

I understand a bill is in the final stages prior to introduction.

Gary C. Hudson, CEO
Rotary Rocket Company

From: (GCHudson)
Subject: Re: Roton ATV to only fly 10 minutes?
Date: 28 Oct 1999 01:19:43 GMT

>Rotary's AIAA paper from last year stated that "Ten to twenty flights
>ranging from hover, to climb, to descent from 8,000 feet altitude will be
>performed under this program."  But it sounds like they aren't planning
>more than one more test (for a total of four), and I wonder whether the ATV
>can even get to 8,000 feet and back in 3.5 minutes.
>One of the strengths of the Roton design, and the ATV prototype, is that it
>can be incrementally tested with moderate risk.  Is Rotary so short on cash
>at this point that it can't afford to carry out the originally planned test
>program?  Would Rotary be confident launching a (non tip thruster) rocket
>powered prototype to altitude with only 10 minutes of flight time on the

There are many factors to consider today with regard to the number of test
flights.  One is risk.  Any failure which results in the loss of the vehicle
and crew would be bad news. Such a failure can occur in a manner which is easy
to correct, but the news reports won't take that into account.  So we fly only
when we absolutely have to.  Second, we have only one vehicle.  Serious damage
to it short of LOV is still bad news.  The PTV will be built with two tails
(well, it actually doesn't have a tail...) so that will be less of an issue.
Third, the simulator worked better than our most fervent hopes, and we can
shorten the flight test program as a result.  The crew has already flown the
sim for many hours of flight time, not minutes.  I can't hurt anyone in the

But to answer the question, the vehicle can fly for about ten minutes.  And the
PTV will be tested in a manner similar to the ATV, we expect, so it will
actually be a "Block 2" ATV.

Gary C. Hudson, CEO
Rotary Rocket Company

From: "Jeff Greason" <>
Subject: Re: Odd propellant mix...
Date: Fri, 29 Oct 1999 17:13:34 -0700

TBotellho <> wrote in message

> The (pre-downsizing) Rotary engine design team seems to be a
> sore subject there, at least the ones who formed Xcor.  I'm told
> that they did not either design or build the peroxide tip
> rockets like they claim on there Xcor web page and that they
> also never actually handled peroxide or concentrated it when they
> worked there.  I was told more than that about them but I'm sure
> I've said enough.

Too much, actually.

> The guys still there are still doing engine work and testing.  I
> guess all there "experts" weren't fired.

I have been, and will continue to be, very circumspect about what
went on at Rotary.  There are many reasons for that.  I signed an
NDA with Rotary not to discuss company business outside -- something
I seem to respect a bit more than whoever you're talking to.  Also,
we're all working in the same business, working on something we care
about very much; I would rejoice to see Rotary suceed, whatever the
odds, and there's nothing to be gained by saying negative things
about them.  Finally, the industry is still small and dynamic; we're
likely to run into each other again, and it is a good idea to stay
polite since we might wind up collaborting in the future.

However, I was both the manager of the overall propulsion effort and
the responsible engineer for those peroxide rockets.  I, personally,
designed several iterations of that rocket, including the flight
version, and people who worked for me and under my direction did most
of the work on it.  Like any development program, many hands touch the
product as it moves from concept to flight hardware, and there were
many who contributed ideas or suggestions or other help.  I feel
completely comfortable claiming that rocket to be one of the
accomplishments in my career, and I'm rather proud of it.

I have handled peroxide.  I have not concentrated peroxide -- that
always seemed a bit too sporty for me.  Two of the people who
concentrated peroxide at Rotary are (as far as I know) still there;
one recently joined the XCOR team.  The craftsman who built
well over half of the peroxide engine components has another job
but is collaborating with us and has told me he will work with us
on future engines.

I'm glad to hear the remaining team at Rotary is still carrying on;
I wish them well and I hope it's true.  However, given the inaccuracy
of the rest of your "inside scoop" material, I'd take anything else
you hear there with a hefty grain of salt.

"Limited funds are a blessing, not         Jeff Greason
a curse.  Nothing encourages creative      President & Eng. Mgr.
thinking in quite the same way." --L. Yau  XCOR Aerospace
   <>                <>

From: Doug Jones <>
Subject: Re: Do small engines have higher T/W ratios? (was mini-engines, 
Date: Mon, 06 Dec 1999 20:30:49 -0800

Robert Lynn wrote:
> The cooling problem is a biggie.  I think the initial Roton rocketjet
> combustion chambers were pushing the limits of size for a continuous
> burn type motor, they used LOX cooling and had SL thrust of about
> 30-40kN per chamber, with chamber pressure of about 20MPa.  The size
> could be reduced somewhat if you used the kerosene and the LOX for
> cooling and got more high tech about the cooling methods.  I would guess
> that if you really pulled out all the stops it might be possible to
> produce a LOX Kero engine with the same chamber pressure one tenth this
> size, but I wouldn't want to bet on it.
> Doug Jones is probably the local expert.

Thanks for the ego stroke :)

Actually, while at Rotary I concentrated on injectors, ignition, and
testing, while Michel Kamel and Jake Lopata did all the really ugly heat
transfer analyses.  I did come up with some clever ideas for cooling
geometries and fabrication techniques (and more since then), but I can't
really talk about the details- proprietary data and all that.  A general
rule of thumb is that heat flux is a function of pressure to the 0.8 power
and dimension to the -.2 power, high pressure and sharp curvature combine
to cause stunning heat flux levels, upwards of 100 MW/m2 in some cases.

Doug Jones
Rocket Plumber, XCOR Aerospace

From: (GCHudson)
Subject: Re: Roton question
Date: 13 Feb 2000 04:01:06 GMT

>I remember someone asking this a few weeks ago,
>but I can't remember the answer.  What was the reasoning
>behind changing the design from the original Roton (where
>you used helecopter blades to assist the thrust at low
>Jonathan Goff

The market requirement grew (> 7K pounds of payload) beyond our confidence in
being able to scale up the original "classic" Roton. Mostly it was a case of
the rotor diameter and the exit area of the tip rockets for high Isp getting
into a mismatch situation. The chamber pressure would have had to exceed 6000
psia, beyond our accepted level for demonstrated technology.

It wa a not a problem with the basic concept, as some have suggested.  One
commentator has mentioned that the rotor wouldn't work at supersonic speeds,
but negelected to explain that an aircraft has already flown with a propeller
at M1.3 in the early 1950s.  And that there is wind tunnel data at M3.5 and
shock tube data at M15.  In the bladed Roton, the rotor stops producing thurst
by the time it reaches M1.3, and then goes to neutral pitch, only providing
pumping force for the engines.

We'd still like to build a small two place Roton someday, but the problem is,
of course, money and time.  There is too little of both.

Gary C. Hudson, CEO
Rotary Rocket Company

From: (Henry Spencer)
Subject: Re: Roton question
Date: Sun, 13 Feb 2000 19:16:05 GMT

In article <>,
Jonathan A Goff  <> wrote:
>...What was the reasoning
>behind changing the design from the original Roton (where
>you used helecopter blades to assist the thrust at low

If I am remembering correctly what I heard Gary say about this, the
problem was simply that the payloads got too big.  The original Roton
ought to work fine at its originally proposed size (Gary said he'd still
like to build it some day), but scaling it up makes the rotor system
considerably more difficult to build, and they decided it was too big
a technical challenge and would scare away investors.
The space program reminds me        |  Henry Spencer
of a government agency.  -Jim Baen  |      (aka

From: (GCHudson)
Subject: Re: Roton question
Date: 17 Feb 2000 05:46:52 GMT

>Gary C. Hudson wrote:
>> It was a not a problem with the basic concept, as some have suggested.
>> One commentator has mentioned that the rotor wouldn't work at
>> supersonic speeds, but negelected to explain that an aircraft has
>> already flown with a propeller at M1.3 in the early 1950s.
>Do you recall the identity of this aircraft? There were two US aircraft
>that conducted tests of high speed propellers in the early '50s, the
>XF-84H and XF-88B, but neither of these were supersonic. Are you
>referring to recent Russian revelations? Is it possible that the M=1.3
>figure you quoted refers to propeller *tip* speed and not actual
>aircraft speed?
>Jim Davis

Jim, I don't have the designation handy.  But there at least one remaining
aircraft on display as a gate guard at the Bakersfield, CA airport.  I think it
is an XF-84 but I am not at all sure. The one thing of which I am sure is that
one such aircraft did fly at M1.3 and also that it made ground crewman ill from
the noise.

Gary C. Hudson

From: (GCHudson)
Subject: Re: Roton question
Date: 18 Feb 2000 17:23:10 GMT

>Here is a URL that has some info on the XF-84.
>The only thing it mentions about supersonic is the specially designed props.
>BTW: The U.S. Air Force Museume is currently restoring a XF-84.

The prop tip is supersonic, yes, but the aircraft reached M1.3 in straight and
level flight.

There is also some interesting video of rotors operating at M3.5 in the Arnold
wind tunnels during the mid-1960s, along with M15 rotor shock tube runs
conducted by NASA Ames in the early 1970s.  Unfortunately, I don't think either
have made it to the web.

Gary C. Hudson, CEO
Rotary Rocket Company

From: (GCHudson)
Subject: Re: Roton question
Date: 19 Feb 2000 05:15:36 GMT

Wales Larrison wrote:


> (GCHudson)
>>The prop tip is supersonic, yes, but the aircraft reached M1.3 in
>>straight and level flight.
>You sure about this Gary?  There is a XF-84H on a pylon outside of the
>Bakersfield airport, but I cannot find any reference to it capable of
>supersonic flight in any source, including aircraft speed records.
>The one at Bakersfield was one of two built, and used to examine the
>impact of high speed propeller-powered flight.


Because my references and files are packed from a move (and I am tardy in
having them unpacked!) I can't give you the reference.  But I'm pretty sure one
run was made at the higher Mach number.  Of course, as my brain cells age,
memory fades, and I could be mistaken.  I seem to recall the data is a pocket
Jane's guide to experimental aircraft published in the early 1980s.  Of course,
the Jane's guide could be wrong, or as I said, I may be mis-remembering it.

The reason it sticks in my memory is that the velocity was nearly the same as
the original bladed Roton ("classic Roton") lost positive thrust from its

Gary C. Hudson

From: (GCHudson)
Subject: Re: has gone downhill
Date: 15 May 2000 21:11:38 GMT

Doug hendrix wrote:

>Derek Lyons wrote:
>> Doug Hendrix <> wrote:
>> >By the way, I can't remember who I had the bet with on Roton not ever
>> >flying  but I think it's time for me to give him the horse laugh!
>> Not really...  Roton has not yet flown.  Gary & Co have operated a
>> really cool helicopter in a Roton airframe, but a lot of Roton's
>> flight envelope remains unvisited.
>Seems like there was a time frame involved on Roton flying. Oh well...

Same time frame as the X-33 and X-34, actually.

The difference is that those projects had full (and in the X-34 case, more than
full) funding, between five times more money (X-34) to over thirty times more
money (X-33).  I'd have been very happy to compete with them, or any other NASA
project, on equivalent budget and time constraints.

I'm not trying to pick a fight with existing or former NASA employees.  Heck,
some of my best friends...  But saying that Rotary (or any of the start-ups)
were unrealistic begs the question of realism in any one of many NASA projects
as well.

Gary C Hudson

From: (GCHudson)
Subject: Re: has gone downhill
Date: 16 May 2000 15:29:08 GMT

Derek Lyons wrote:

> (GCHudson) wrote:
>> But saying that Rotary (or any of the start-ups) were unrealistic begs the
>>question of realism in any one of many NASA projects as well.
>Gary, I hope you did not get the above from my quote (below);
>>>Derek Lyons wrote:
>>>> Not really...  Roton has not yet flown.  Gary & Co have operated a
>>>> really cool helicopter in a Roton airframe, but a lot of Roton's
>>>> flight envelope remains unvisited.
>I did not mean to imply that Roton was unrealistic, but rather that it
>remains unproven.  It's an article of faith among some in this group
>that last years flight tests were a prelude to serial production as
>opposed to being the first of several in the flight test series.

Derek, by no means.  Roton was a high risk, high payoff project.  In fact, it
was more akin to a commercial X-vehicle than a pre-preproduction prototype. And
there is no doubt in my mind that if we had the funds to take it further to a
rocket-powered prototype it would have been significantly modified before it
ever got to "production".  Given the small market for space launch, there would
have only been a couple vehicles built in any case, rather like the Shuttle,

Gary C Hudson

From: (GCHudson)
Subject: Re: Rotary Rocket: what happened?
Date: 30 Jun 2000 15:21:13 GMT

>Which plan was that? The one where liftoff was achieved by using big-ass
>rockets on the tips of rotors? The one with telescoping rotors? The one
>with the rotating rockets? The one with the Fastrak engine?
>Say what you will about any of the concepts Rotary put forth... but when
>the basic notion of the vehicle keeps changing, you know it's never
>good. At least with companies like Pioneer and Kelly, while the mold
>lines might change weekly, at least the basic mission and concept
>remained unchanged.


I might have hoped for a little more understanding of the business from you.
As you probably know or can calculate, the original Roton, while feasible (no
matter what Zubrin says) had a payload limit which was too small for the
customer's requirement (i.e., the third or fourth iteration of the Teledesic
spacecraft).  Otherwise it is the one we would have built.  Cetainly Bevin and
I wanted to!  The "version" with telecopic rotors was never a baseline vehicle
within the Company (though the design was once considered along with many
others when we had to abandon the bladed Roton due to market, not technical,
conditions).  But it was used for the announcement of the project because
illustrations were available and the press doesn't care about the details.
Frankly, I also enjoyed spreading around a bit of disinformation.  Helps you
find out who are your friends and who are not.

The Rotary engine could have been built (ask any of the ex-propulsion team),
but the reason I killed it was simple.  We were trying to raise money and it
was hurting, not helping.  The "Fastrac" was a politically useful engine (or
should I say, its future derivative engine) to employ.  It's not like anyone
else ever proposed changing powerplants; Kelly has never settled on one but
proposed many, and so has Pioneer (including variations in upper stages). Need
I mention the difference between the pre-Pioneer peroxide Black Horse and the
current Pioneer lox-kero vehicle?  Len Cormier has proposed many, many
variations on the theme of TSTO for which I salute, not condemn, him.  Kistler
has gone through many, many variations.  I am not complaining about these firms
changes; this is real life.  It means they know what they are doing, responding
to changing conditions.  Once again, by the way, the business is changing:
people and spacecraft, will be what drives the future commercial RLV market, if
anything does.

The essence of building a commercial space transportation company is finance,
not engineering.  The basic mission remained largely unchanged, even if there
were technical alterations.  Fail to acomodate to your customer's/investor's
wishes and you absolutely won't succeed, either in finding funding (which we
did pretty well, but even so not well enouugh) or finding launches.  You'll end
up with a technically pure venture which will go nowhere.  Or like NASA, doing
mostly technology sandbox stuff.

Gary C Hudson

From: (Henry Spencer)
Subject: Re: Hudson left Rotary
Date: Sun, 2 Jul 2000 17:06:47 GMT

In article <>,
Graham Nelson  <> wrote:
>What Mr Hudson has in fact been doing is trying to provide a launch
>system for small satellites in LEO, a market which looked very
>lucrative four years ago, and which now looks much less promising.
>Business is like that. It's ridiculous that Mr Hudson has to carry
>the hopes of endless zealots on his shoulders.

Actually, Gary is one of us zealots.  Circumstances required that he be a
practical businessman, focusing primarily on the most immediately
promising market, for the sake of getting things started... but in its
heyday, Rotary had one eye fixed on more-ambitious long-term goals.  They
were concerned about certain issues that wouldn't matter for LEO satellite
Microsoft shouldn't be broken up.       |  Henry Spencer
It should be shut down.  -- Phil Agre   |      (aka

From: (GCHudson)
Subject: Re: Rotary Rocket: what happened?
Date: 02 Jul 2000 17:17:36 GMT

Scott wrote:

>My concern with regards to this wasn't how effective a propellor this
>would be in super/hypersoinc regime... but how much of a drag device it
>would be, and how hot would it get. Rememebr these things would be:
>1) Unswept.
>2) Going at a faster airspeed than the vehicle itself.
>3) Shedding shock waves.
>4) Being hit with shockwaves from the nose.
>5) Interacting with each other's shock waves.
>I do not know if these are insurmountable problems... but they do seem
>pretty stout, and I have no wind tunnel test references to fall baclk on
>either way. So I'd guess that the system would work great at launch...
>high pressure and thrust, with effective Isp's over 500 seconds (via
>thrust from the air)... but past Mach 1, performance woudl drop
>drastically, and quite possibly go well below a standard engine, and
>thoughouhly screw up vehicle aerodynamics. I can see why (and agree
>with) the decision to go with the rotary rocket.
>If someone can point to wind tunnel tests of something like this, I'd
>love to see 'em.

Arnold ran rotors to M3.5, and the videos and data are available; Ames tested
at M15 in the shock tube and we ran CFD across a range to M25.  I don't have
references handy, you'll have to hunt them down same as we did.  Most date from
1965-1971.  In fact, we had one fellow on staff who ran the Ames project.

For most bladed Roton designs, the rotors were in the wake and not subject to
serious ascent heating or shocking.  Typical heating rates on ascent would have
been 35-40 BTU sq ft-sec, about the same as descent.

No thrust was expected past M1.3, at which point the rotor drag predominates,
but once you integrate performance under the curve you find the rotor paid for
its own weight.  It gave a trajectory-averaged Isp of about 375 sec, which was
also useful.

The only reason we want with the rotary engine was the bladed Roton would have
not been able to carry the larger spacecraft customers wished to orbit.  The
major issue was the size of the engines on the rotor tip, which as the vehicle
became heavier of course become larger, producing more drag and other problems.
 I have pointed out all these issues many times before.

Gary C Hudson

From: (Henry Spencer)
Subject: Re: Rotary Rocket: what happened?
Date: Sun, 2 Jul 2000 21:17:28 GMT

In article <>,
Scott Lowther  <> wrote:
>All in all, I still like the rotary rocket better. Though again, the
>number of individual combustors is also a concern (what was it... 92 or
>something?), as getting that many engines to ignite simultaneously
>andreliably is no mean feat... whether the rockets are rotating or not.

This just means doing serious work on making ignition reliable.  It's not
magic, just careful engineering.

Remember also that the only time you need ignition of all the chambers is
when you're on the ground, and any serious problem in that department can
probably be handled by just aborting the takeoff.

>...But if the cluster is rotating and it has some hard
>starts, the thing could get off balance in a hurry and tear itself to

If a chamber fails to start, shut down the opposing one to keep things in
balance, and then you've got some time to think about either aborting the
takeoff or trying the ignition again.  Computers have no problem with
dealing with such things on millisecond time scales.

Hard starts are a symptom of bad engine design, more specifically
inadequate igniter design (or excessive faith in hypergolic ignition).
Microsoft shouldn't be broken up.       |  Henry Spencer
It should be shut down.  -- Phil Agre   |      (aka

From: (GCHudson)
Subject: Re: Rotary Rocket: what happened?
Date: 02 Jul 2000 23:43:42 GMT

Henry Spencer wrote:

>In article <>,
>Scott Lowther  <> wrote:
>>All in all, I still like the rotary rocket better. Though again, the
>>number of individual combustors is also a concern (what was it... 92 or
>>something?), as getting that many engines to ignite simultaneously
>>andreliably is no mean feat... whether the rockets are rotating or not.
>This just means doing serious work on making ignition reliable.  It's not
>magic, just careful engineering.
>Remember also that the only time you need ignition of all the chambers is
>when you're on the ground, and any serious problem in that department can
>probably be handled by just aborting the takeoff.
>>...But if the cluster is rotating and it has some hard
>>starts, the thing could get off balance in a hurry and tear itself to
>If a chamber fails to start, shut down the opposing one to keep things in
>balance, and then you've got some time to think about either aborting the
>takeoff or trying the ignition again.  Computers have no problem with
>dealing with such things on millisecond time scales.
>Hard starts are a symptom of bad engine design, more specifically
>inadequate igniter design (or excessive faith in hypergolic ignition).

We conducted some tests at Rotary where the ignition device was external to the
chamber, and the engine ignited just fine with no overpressure.  It was our
conclusion that for these high pressure chambers we could tolerate ignition
failure in a few and that plumes from adjacent chambers would ignite the
chambers which failed with no problem.  Before doing such tests I would not
have belived this, which just points out the value of doing and not just

Gary C Hudson

From: (GCHudson)
Subject: Re: Hudson left Rotary
Date: 09 Jul 2000 05:45:53 GMT

>On the subject of technology, did Rotary in retrospect spend the $30
>million or so invested in the wisest possible manner? Instead of an ATV,
>would it have been better (again purely in retrospect) to build a
>prototype RocketJet engine, thoroughly ground test it, and then launch
>it on an expendable vehicle in a test of the engine and the center of
>gravity shifting control scheme? Would a successful test have encouraged
>further investment unlike the successful ATV tests? This is not to
>criticize the decisions that Rotary did in fact make but in light of
>what is now known would another approach have been preferable?
>Jim Davis

After the fact is is easy to agree that we should have spent the money
differently.  But you have to make the determination of how to allocate
resources based on the business plan we were following.  In 1996, when the
company was founded, we were told by customers we had to demonstrate orbital
flight of our RLV by 2000 in order to gain orders.  We thought we could do
that, and one think we proved was that we could build and flight test hardware
for a tiny fraction of what others thought it cost, and actually, for less than
_we_ thought it cost.  We conducted successful tests of engine and the ATV, but
it didn't make a difference.  Pioneer, Kelly and Kistler had/have very vanilla
vehicle concepts and it didn't make a difference for them, either.

The problem was not lack of financing; it was lack of market.  And we had a
schedule to meet, so we couldn't take three or four years to prove only one
element of the vehicle; all had to be done simultaneously.  Was that the right
thing to do?  Heck no.  Was there a choice?  Nope.

Gary C Hudson

PS: I don't know where the idea of shifting Cg as a means of control came from.
 It certainly was never a baseline for the vehicle, even though a few folks
around the company promoted the notion.

From: (Henry Spencer)
Subject: Re: Hudson left Rotary
Date: Sun, 9 Jul 2000 22:20:42 GMT

In article <>,
James A Davis  <> wrote:
>> Most of them have something workable, in the technical sense.  What they
>> don't have is *money*, and that has nothing to do with the technical
>> soundness, or lack thereof, of their ideas.
>Is this your opinion or do you know this for a fact? It seems to me that
>at least *some* prospective investors would have questioned whether a
>$150 million budget was adequate to bring advanced concepts like Roton
>to service even had the market been there...

As Gary has already noted...  (a) The more conservative RLV designs are no
better funded than the ambitious ones -- indeed, Roton attracted *more*
money than several less-risky concepts.  (b) Rotary demonstrated that its
cost estimates for the early phases were reasonably accurate, and although
this doesn't automatically prove that they'd stay that way through
order-of-magnitude growth, it does boost one's confidence a lot.

>It's possible of course that
>prospective investors looked at the market first and, not liking what
>they saw, never did any serious technical evaluation.

As witness Rotary's move away from the rotary engine in response to the
concerns of potential investors, at least some of the investors were
paying attention to the technical issues.

>On the subject of technology, did Rotary in retrospect spend the $30
>million or so invested in the wisest possible manner?

Possibly not, but second-guessing them requires considering not just the
basic objectives, but also the constraints.  Particularly notable was the
belief that they didn't have much time if they were going to be ready when
their major customers wanted to fly; at Space Access 97, Gary said "we'll
be flying in three years or out of business".
Microsoft shouldn't be broken up.       |  Henry Spencer
It should be shut down.  -- Phil Agre   |      (aka

From: (Henry Spencer)
Subject: Re: Hudson left Rotary
Date: Sun, 9 Jul 2000 23:24:01 GMT

In article <8k9j2g$s9u$>, BigPilot <> wrote:
>>The key is that you call the guy in the cockpit a *test pilot*, not an
>That was not the issue here. They actually wanted the vehicle to be piloted;
>not just in the test fase but during routine flights as well.

Yep.  Just like an aircraft.  You know, the gadgets that carry millions of
people a day, with near-infinitesimal failure rates, in a large and
profitable industry?  Rotary was consciously trying to get *away* from the
standard artillery model of rockets, with a tiny industry supported by a
few cost-is-no-object customers who grit their teeth and live with failure
rates which would be intolerable in any other branch of engineering.

>If I were to
>design a revolutionary device such as the Roton, it certainly wouldn't be
>human piloted. That's simply too dangerous.

Dangerous to who, and to what?  Crashes are dangerous to your company's
financial health... and no unmanned aircraft has yet been developed
without at least one write-off-the-vehicle crash.  And how many non-human-
piloted airliners have you flown on?  (You can bet that Boeing knows
exactly how much a dead passenger costs.)

>You have to look at it from a
>business stand point as well. If you lose a pilotless vehicle than it's
>simply too bad but if you lose a human life as well the project will be
>unsalvageable due to ethical concerns.

Utter nonsense.  People die *all the time* in business projects; the
projects do NOT get written off "due to ethical concerns".  Any major
construction project *expects* to kill a few construction workers --
insurance is part of the budget, and you'd better believe that projections
of the expected fatalities figure into that.

>This is a business where talking
>about not some NASA experimental vehicle so your comparison with a test
>pilot doesn't hold.

Why not?  Please explain.  Businesses use (and sometimes have to bury)
test pilots too.

>Anyway, NASA is also moving towards smaller, autonomous,
>pilotless, scaled prototypes.

For some things, not for everything.  And they may change their minds
after they've actually *tried* a few of those.  Their past experiences
with that approach have not been encouraging.  (Yes, it's been tried

>> (No investor in his right mind wants to back somebody who's competing
>> against the government.)
>If you look at NASA's achievements then I can safely say that they won't
>have something within 5 years that will be as simple and focused as for
>example, the Pioneer spaceplane.

Certainly not.  But they may have something which *claims* to address the
same markets as Pioneer.  Or they may have picked a favorite contractor to
try to develop something like that.  Even that is the kiss of death for
private ventures; one of Gary's earlier launcher projects died when ARPA
anointed Orbital Sciences as the government's chosen small-launch supplier.

>...It will be quite a while before NASA
>designs a shuttle which is as cost effective as for privately financed
>shuttles simply because the contractors that work on the project don't have
>the incentive to build a $20 million space shuttle.

They don't have to.  NASA can afford something much more expensive.  It
still kills the funding for private competitors, especially if it's
undertaken as an "industry-government partnership" -- another recent fad
for NASA -- because that means a government-subsidized project that's
going after commercial markets as well as government ones.

>So if these investors
>have half a brain they will continue to back the Pioneer space plane or some
>other promising technology.

Historically, it does not work that way.  They pull out.  It's happened.
Microsoft shouldn't be broken up.       |  Henry Spencer
It should be shut down.  -- Phil Agre   |      (aka

From: (GCHudson)
Subject: Re: Hudson left Rotary
Date: 10 Jul 2000

Geoffrey A. Landis wrote:

>In article <> Henry Spencer,
>>>...It will be quite a while before NASA
>>>designs a shuttle which is as cost effective as for privately financed
>>>shuttles simply because the contractors that work on the project don't have
>>>the incentive to build a $20 million space shuttle.
>>They don't have to.  NASA can afford something much more expensive.  It
>>still kills the funding for private competitors, 
>Henry, you often see this blindly stated as if it were a fact on
>space.policy, but there has never been any credible evidence for this
>The unfortunate fact is, business investors don't like risk.  Once the
>failure of Iridium to materialize as a major launch market added market
>risk to technical risk, the private ventures had an impossible time
>convincing investors.  Even the comparatively low technical risk ventures
>like Kistler are having a tough time.  There's no need to say "NASA"
>killed the funding for private competitors; the market did it itself.
>[Globalstar, if it succeeds, may yet turn that around (we can hope).  But
>right at the instant the market is not looking good for private orbital
>launch capability.]
>>especially if it's
>>undertaken as an "industry-government partnership" -- another recent fad
>>for NASA -- because that means a government-subsidized project that's
>>going after commercial markets as well as government ones. 
>No, again, no evidence for that.  Venture capitalists tend to be very
>fierce free-market advocates; I don't think that I've ever met a single
>one who doesn't completely believe that a private venture will
>out-compete a government one.  It is the market risk and the technical
>risk that obsess them, and they're not impressed in the argument "if you
>build the launcher, the markets will come".
>[nb: the above statements are subject to change if Gary Hudson (who
>surely has a better understanding of investor psychology by now!) cares
>to correct my comments with a differing opinion...]

We could spend days discussing the financing problems of start-up launch
companies, and I don't have the time (or the intererest any longer!) to do

But, I can say:

1) VCs were never interested in us or likely in any launch firm, simply because
the market is too small.  VCs like firms to have the potential to do a billion
in sales in five years, which suggests the launch company has almost 50% of the
existing world commercial launch market (about $2.3 billion) within that five
year time frame.  Can that happen?  Possible, but unlikely, unless one lowers
launch costs dramatically and gets customers to move to your company.  But if
you do that, the total market size declines and now you need 70-80-90% or more.
 No one will believe that is achievable, even if it is possible.

2) Angels and customers are the only places you can go for initial funding. 
(Suppliers won't work.  They are either larger aerospace firms that have no
interest in seeing you succeed because they are competitors, or they are
vendors of high value components such as engines.  If you are an RLV company,
the engine guys don't like you because you are going to buy so few.  So no
money there.  And besides, they don't have much cash anyway.)  Customers have
to get funds too, so they can't team up with new launch firms because their
financial advisors/investment bankers won't let them.  (This is why
Merrill-Lynch forced Teledesic to team with Boeing, which was a disaster for
Teledesic.)  Angels are all that are left, and they are few and far between. 
Almost none of them have the money to fund such a project alone.  And yes, we
did talk to Paul Allen, etc.

3) Gov't funding helps the start-up launch company by providing credibility,
which is very useful, but costs by torquing one's business plan and schedule,
not to mention other problems.  But there won't be enough of such funding to
build a vehicle and most investors don't want to be tied to a gov't project. 
They will tolerate loan guarantees, tax-free industrial bonds, etc., but those
take years to put into place and then favor the established firms.  That is one
reason we opposed them at Rotary.


From: (GCHudson)
Subject: Re: ROTON, ca. 1932
Date: 10 Jul 2000 15:07:27 GMT

Scott Lowther wrote:

>Just read something I thought might be of interest:
>"Shtern, of Osoaviakhim's Air Equipment Design Bureau undertook the
>design of the LRD-D-1's liquid propellant engine. Shtern pursued a
>unique solution to the problem of forcing liquid oxygen and gasoline
>into the rocket's combustion chambers. His was a rotary engine, in which
>two combustion chambers spun rapidly around the rocket's vertical axis.
>Centrifugal force would feed propellants through radial pipes into the
>two chambers. Spin would be maintained by off-axis thrust from each
>nozzle. Each nozzle would be directed straight back, but the lower ends
>of the expansion nozzles would be cut diagonally. Not only would the
>engine's spin provide fuel pressure, it would also add stability."
>However, there's also this: "By March of 1935, it became clear that
>Shtern's innovative design was unworkable..."
>This from Pete Alway's "Retro Rockets   Experimental Rockets 1926-1941"
>Similarly, an American named L.H. Leonard (has anyone ever heard of
>him???) recieved several patents for VTOL aircraft, starting about 1941.
>One of his early designs was a tailsitter that used stumpy wings located
>on a rotary collar located about 1/3 of the way up the landed vehicle;
>propulsion was provided but a gasoline/air rocket motorlocated in each
>wingtip. Liftoff and flight were as with the Treibflugel, for those of
>you who know that one. The air was fed into the rockets by means of a
>body mounted compressor of some type (this was something that certainly
>could have been improved upon), while the gas was centrifugally pumped.

We were aware of both these ideas, and in fact, the Leonard patent is ref. 1 in
the Roton patent.  Any number of centrifugal pumped rockets have been proposed
and some tested.  Reaction Motors built and successfully tested a combination
rotary engine and pumped engine (Two chambers each) in the mid forties.  The
rotary portion was used to drive the centrifugal pumps!  Rather amusing.  The
Russian work probably failed because of runaway acceleration or possibly
because of cooling problems at the high chamber pressure created by the

Gary C Hudson

From: (GCHudson)
Subject: Re: MirCorp's economic success highly unlikely?
Date: 11 Jul 2000 02:14:42 GMT

Jim Benson wrote

>I suspect Walt Anderson trusts the people he invests in, therefore I
>doubt he micromanaged Roton.  My only point was that companies Walt
>has started and run himself have been very successful. I did not say
>anything about companies he simply invests in - that is a completely
>different issue, and one I know little about.  That's all  :-)

All I'll say about this is that Walt Anderson is a fine fellow, and a savvy
investor  who did not micromanage me.  If _anyone_ can make a success out the
MirCorp effort, it will be him and his team there.

Gary C Hudson

From: "Jeff Greason" <>
Subject: Re: Risk Free Testing was (Re: Hudson left Rotary)
Date: Mon, 10 Jul 2000 21:35:07 -0700

Alan Anderson <> wrote in message
> Jonathan A Goff <> wrote:
> > ...Computers can pilot rockets, and in fact
> > have done so for almost the entire history of rocketry.
> They do so quite long as nothing goes wrong.  The history of
> rocketry is full of examples where something goes wrong and the
> rocket-powered vehicle goes out of control.  Piloted vehicles have a much
> more sophisticated program running the show.

My preference for piloted craft during experimental development programs is
well known by now.  Certainly, the "objective" factors, such as intelligent
responses in the event of an unexpected situation, and the high cost and
low quality of software, are important elements in the lower failure rate
of piloted vehicles at similar or lower cost to UAVs.

However, now that I've seen some development programs which *did*
involve piloted craft, and can contrast that with other programs which
did not, I think there's another, even more important factor.  The design
philosophy of the whole vehicle is quite different in a piloted vehicle.
I could rant about the importance of quality control and mission success
until I'm blue in the face, and it wouldn't have the impact of
the simple statement "remember, you may be in the right seat".

As I've pointed out before, management's attention and energy is a
critically limited resource on agressive projects -- and piloted vehicles
tend to automatically lead to an engineering culture where the
importance of "graceful" failure modes and realistic aborts are given
serious attention.  During the design of unmanned craft, these issues tend
to be given a great deal less attention -- after all, there are *always*
deadlines looming and performance pressures, and there aren't enough
managers to run around making sure everyone is doing what they're
"supposed" to be doing in making those decisions.

I suspect (but of course, this is just my opinion) that this is the reason
for the horrible results of "man rating" expendable vehicles, and why
the development of UAV's tends to be even worse than the combination
of the development of a manned vehicle and the work to turn a manned
aircraft into a drone.  As in so many other areas of engineering, the
results are path-dependent; it really does matter how you get there.
(Analogous factors explain why it generally does wind up taking less
 time and money to do X-vehicles then Y-vehicles then production
 with incrementally improved models than it does to jump directly
 to the final vehicle -- a counterintuitive result).

"Limited funds are a blessing, not         Jeff Greason
a curse.  Nothing encourages creative      President & Eng. Mgr.
thinking in quite the same way." --L. Yau  XCOR Aerospace
   <>                <>

From: "Jeff Greason" <>
Subject: Re: Risk Free Testing was (Re: Hudson left Rotary)
Date: Tue, 11 Jul 2000 17:51:13 -0700

<> wrote in message
> In article <>,
> (Jens Lerch) wrote:
> > Ariane 5 Flight 1
> > A variable overflows in the trajectory subsection of the program,
> > causing the guidence system to think that the rocket is off course and
> > it tries to correct the flight path by swiveling all three engines to
> > their maximum deflection, causing the vehicle to fly sideways.
> > A pilot would have centered the engines as soon as he had seen the
> > maximum deflection.
>   And then what?  Unstable launch vehicles need computer control to
> keep them pointed in the right direction.  The computer was out to
> lunch.  Being able to abort the flight if something is going horribly
> wrong is nice, but this is not equal to being piloted.

This is a perfect example of what I meant in my previous post about
the whole philosophy of piloted vehicles being different from UAV's
or expendable launchers.  Given a control problem such as instability,
the first reaction of a team designing a piloted vehicle is "Hmm, I
guess we'd better see about improving vehicle stability so the pilot
can fly it without the computer", and the first reaction of a team
designing an unpiloted vehicle is "Gee, I guess we'd better add some
people to the software development since the control laws are
getting ugly".  Multiply by the number of design decisions...

By the way, "stability" is not a black & white thing -- the Titan III
launch vehicle is not positively stable throughout the flight regime;
nevertheless, extensive ground simulation with pilot in the loop
showed that the Dyna-Soar pilots could in fact manually fly the
vehicle in the event of a computer failure (because the pilots
essentially refused to put their ass on the candle until this was

"Limited funds are a blessing, not         Jeff Greason
a curse.  Nothing encourages creative      President & Eng. Mgr.
thinking in quite the same way." --L. Yau  XCOR Aerospace
   <>                <>

From: (Zerog)
Subject: Re: Pilots and Vehicle Reliability
Date: 12 Jul 2000 01:41:16 GMT

I really don't have time to get tangled up in a lengthy discussion, but after
reading Mr. Wright's excellant summary, I just can't resist inserting a few

First let me congratulate Jeff Greason on eloquently presenting the points
regarding the design discipline that is instilled in an engineering team when
there is a crew on the vehicle.  I have a hard time not reducing this subject
to a Dennis Miller type rant.

Second, I'd like to remind the readers that the Roton was a commercial
development, and as such, schedule and budget have a funny way of cutting
through theoretical rhetoric and illuminating reality.

Putting a crew on the Roton was the most cost-effective path toward rapid, low
cost development of a reliably reusable vehicle.

Example - The Roton was designed to land using a rotor.  Developing an
auto-landing system for a helicopter, something that as far as I am aware has
not yet been achieved commercially, was a task that was estimated to take over
18 months and cost in excess of $3M.  This much time and money was not
available, and even if it had been, analysis showed that a manually controlled
landing was more reliable, especially during the first critical landing
operations of a new hardware development program.

Example of an Example - Tomorrow morning I could buy a fully instrumented Beech
Bonanza set up for ILS approaches for <$200k.  Tomorrow afternoon, with an
appropriately trained pilot (I'm not IFR rated), I could shoot ILS approaches
through the evening and into the next morning, over and over, safely and

On the other hand, if I wanted to automate that process, a "simple" link
between instruments and effectors, I'd need to spend a whole lot more, and it
would take considerably more time to accomplish than the 24 hrs mentioned
above.  I don't have the time, don't have the money, and guess what?  I'd
rather not trust my brand new (well, used) Bonanza to an automated approach
controlled by an as yet untested system.

Rotary Rocket had a very small budget and faced a very tight schedule.  For the
cost the salaries needed to hire experienced test pilots, who by the way were
also excellent engineers, Rotary was able to avoid developing an auto-land
system for a helicopter, and in the package, it got a whole lot more.  Both
from the standpoint of reduced hardware development costs, and the discipline
in testing that was provided by the crew.  As a side benefit, Rotary got a
better design because our friends were flying it.  Believe me, you don't want
to think about what it would be like to tell a friend's widow that you were
pretty sure it would work, so you didn't bother checking your calculations.

Time doesn't allow a complete discussion of the benefits and advantages that a
crew's presence brought to the Roton configuration. Suffice it to say that
Rotary determined early on that the vehicle would be more complex, costly, and
less reliable without a crew.  The key is that the Roton was not an unmanned
vehicle with a crew compartment attached, the crew was part of the design and
was used to the maximum extent to reduce the complexity of other systems.  In a
configuration without a crew, more redundancy would have been needed in many
systems to maintain reliability.  In many cases, it was determined that the
crew could provide the necessary back-up redundancy without additional hardware

The Crew who flew the ATV test vehicle had many thousands of hours flight time
in high performance aircraft as well as specific training in flight test
operations.  Uncle Sam paid in excess of $50M for that experience and training.
 Rotary Rocket got a first class bargain.

BTW - The Roton was intended to carry not only inert cargo, but human cargo as

Bevin McKinney

From: (GCHudson)
Subject: Re: Hudson left Rotary
Date: 12 Jul 2000 04:50:24 GMT

Phil Fraering wrote:

> (GCHudson) writes:
>> >> financial advisors/investment bankers won't let them.  (This is why
>> >> Merrill-Lynch forced Teledesic to team with Boeing, which was a
>> >> disaster for Teledesic.)
>> >
>> >Just wondering, but could you explain the chain of logic there a bit
>> >more?
>> >
>> >Phil
>> Sure.  But there are several separate thoughts in that paragraph;
>> which one is unclear?
>How precisely was Boeing a disaster for Teledesic?

That answer would take hours to write, but the short version is Teledesic was
conceived as an bold firm which would fund cutting edge technology to build
very advanced spacecraft.  (Many spacecraft (800+) with very advanced power,
comm, crosslinks, etc.)  Once Boeing got a hold of the plan, the system was
rapidly "dumbed down" into mediocrity.  The capability was decreased, the cost
remained unchanged and the economy of scale was eroded by having a much small
constellation size.  In the end, it was simply Iridum writ large; in fact, it
then became so, since after Teledesic dumped Boeing they got into bed with
Motorola, the Iridium architects.

One can argue this was a natural evolution; I argue it was a natural corruption
of a profound idea.  But that's all I'll say, since I don't want to be drawn
into a protracted discussion.

Gary C Hudson

From: Doug Jones <>
Subject: Re: ROTON, ca. 1932
Date: Thu, 20 Jul 2000 17:20:56 -0700

Jim Bowery wrote:
> We should be able to set FeedPressure (pressure from the tankage), Dens,
> InjectorDischargeCoefficient, LiqTubes, ChamberPressure,
> TangentialVelocity and Thrust to reasonable values and solve for the rest
> of the variables with NozzlePitch ending up somewhere between 0 and 1, right?
> If not, where does the missing variable come in?  Heat from flow friction
> at the injector?

Liquid flow through an orifice wimps out at higher pressure:


Thus for fixed geometry the chamber pressure doesn't rise indefinitely,
the Isp doesn't rise indefinately, and the system is stable.

(At RRC, I was Keeper of the Wheel Dynamics Spreadsheet.)

Doug Jones
Rocket Plumber, XCOR Aerospace

From: (Henry Spencer)
Subject: Re: Rotary Rocket...
Date: Mon, 24 Jul 2000 16:27:03 GMT

In article <>,
Anthony Roberts  <> wrote:
>For those familiar with the Rotary Rocket, I have a question. The heat
>sheild is at the bottom of the vehicle, as is the engine. How is the
>engine protected from the effects of re-entry?

Probably the same way the rest of the vehicle is protected:  by bleeding
a small amount of coolant (water) out through it.
Microsoft shouldn't be broken up.       |  Henry Spencer
It should be shut down.  -- Phil Agre   |      (aka

From: (GCHudson)
Subject: Re: Rotary Rocket...
Date: 24 Jul 2000 16:44:29 GMT

Anthony roberts wrote:

>For those familiar with the Rotary Rocket, I have a question. The heat
>sheild is at the bottom of the vehicle, as is the engine. How is the
>engine protected from the effects of re-entry?

The baseline was a transpirational water cooled applique attached to the
composite structure.  The applique was fabricated from foils which had been
photo etched with cooling and venting galleries and then diffusion bonded
together.  We also built similar stuctures from copper foil for main engine
regenerative cooling.

Gary C Hudson

From: (GCHudson)
Subject: Re: Hudson left Rotary
Date: 30 Jul 2000 00:41:54 GMT

Phil Fraering wrote:

>>"Michael P. Walsh" <> writes:
>> I will chime in with my opinion that perhaps Gary Hudson and
>> Rotary Rocket were just a bit too far ahead of the pack for a
> >truly commercial system.  I have believed ( and posted comments
>> in this newsgroup in the past ) that the Roton program was a
>> very well planned X program that would revolutionize the space
> >launch business if it succeeded.
>AFAIK, Rotary did have technical changes of direction, but all the
>technical stuff and testing they did do was apparently successful.
>They ran out of investment money before they ran into significant
>technical failures; and Gary himself has said that they ran out of
>investment money because the market evaporated, partly because of
>changes in the Big Communications Constellations, and partly because
>things just aren't looking good for the Big Comsat Constellations
>at the moment. You could say that Roton collapsed under the weight
>of all those re-entering Iridiums.
>(I wonder how much Kistler's spent by now, in comparison, and
>how much more they need to spend to make it).

George Mueller testified, sitting next to me at a House hearing late last year,
that they had spent $500 million and needed $300 million to reach first flight.
 I have subsequently been told that " to reach first flight" number to be both
$400 and $500 million from Kistler staff.  Rotary spent about $33 million.

Gary C Hudson

From: (Henry Spencer)
Subject: Re: Roton on the moon
Date: Tue, 10 Oct 2000 02:38:54 GMT

In article <_hsE5.7262$>,
Jeroen <> wrote:
>> >As a general rule, it is completely inefficient to use a single vehicle...
>> Correct, but it may nevertheless be the preferred solution, when you
>> factor development costs in...
>I doubt Roton could be used to get to the moon, land, take of, go back to
>earth and land again wihtout major modifications.

I'm less sure of that.  Rotary always struck me as having its eye on
long-term goals as well as short-term ones; certainly in the past, the
ability to go farther afield has been an explicit feature of Gary Hudson's
SSTO designs.  I'd be very surprised if it hadn't been at least thought

>...What about life-support for a longer time
>than a typical Roton launch? Or, if you prefer to avoid that problem by
>removing the crew, aviaonics?

Add another battery, another oxygen tank, and a box of sandwiches, as part
of the payload.  There are things you need, but they aren't huge.

>Is Roton's engine restartable in flight?

No positive info, but I'd be surprised if it wasn't.  Ability to operate
with fairly austere ground support was an explicit feature, to lower
operations costs.

>How would Roton land without an atmosphere for its rotor (despite
>the lower gravity)?

On rocket thrust.  The engine was throttlable.
Microsoft shouldn't be broken up.       |  Henry Spencer
It should be shut down.  -- Phil Agre   |      (aka

From: (GCHudson)
Subject: Re: X-33/Venturestar Question...
Date: 13 Nov 2000 17:53:36 GMT

>It just amuses me that some of the biggest critics of lumping all the new
>technological features into the X-33 program are/were also some of the
>biggest cheerleaders of the Roton, a vehicle which also overflows with
>technical innovation.
>Of course the folks at Rotary were considerate enough to use their own
>Jim Davis

Loathe am I to jump into this discussion, but I should also comment that we
innovated only when we were forced into it by circumstances.  And our
innovation was limited by dollars and more importantly, time, which was (we
thought) the biggest challenge facing us.  We conducted development of
water-cooled thermal protection using platelet technology, tested composite LOX
tank technology (with 120+ cycles on tank walls using LOX plus heating to
simulate re-entry temperatures), and performed many successful test firings of
high pressure LOX cooled regenerative chambers, not to mention building and
flying the ATV, which was a mass fraction demonstrator as well as a landing
demonstrator.  All this was done for less money than the overrun on the X-33
engine effort.  And the entire project could have been completed for the
interest on that $1.4 Billion spent on X-33.

In the end, I think the issue is not should X-33 (or NASA) be testing new
technology, but rather should the amount of money spent on X-33 have been
better spent on a prototypical space transportation system?  Generally, one
wants to spend about 10-15% of available development funds on new technology,
while the balance goes to building and flying something which generates revenue
so that the cycle can continue.

The argument is therefore between those who think we have all the technology we
need to get a first generation reusable spaceship and those who don't.  As you
might expect, I am in the camp of the former, notwithstanding the fact that I
ran the Roton project, which had imperatives leading to the decisions we made
which I can't discuss in this forum.

Gary C Hudson

Date: Sat, 10 Feb 2001 23:05:53 -0800
From: Doug Jones <>
Subject: Re: Rotary Scramjet? (Rotary Rocket)

Bevin McKinney wrote:
> Boy.  Isn't it amazing how long a thread can run with discussion running back
> and forth arguing a point of seemingly little consequence?

You're entirely correct- the thread had drifted from RLV landing methods
to power-off autorotation landings of large helicopters, and I responded
to that. Thanks for pointing out that *that* topic isn't exactly what's
of interest here.

> All helicopters can fly in autorotation.  All airplanes can glide.
> However, a lot of helicopters are a handful to land power off, as are a
> lot of airplanes. I wouldn't want to land a high-speed jet deadstick on
> a short field, although I guess it could be done in an emergency.

Yeah, I've done over a hundred landings in low L/D vehicles (if you use
the term vehicle loosely), and having low wing loading makes it far
easier.  I read about young maniacs jumping on ram-air wings at 3x the
area loading that I ever used and I cringe- some of these things ain't
big enough to make a decent tablecloth. (That's a thread for another
day, too.)

> If it's good unpowered autorotation landing characteristics you want in
> a rotary wing aircraft, it is certainly possible to design for this,
> just as good deadstick landing characteristics can be designed into
> conventional aircraft. That's part of why 14 year olds can get student
> glider licenses.
> All in all, I think the Roton concept used an appropriate compromise.  A
> rotor that had marginal landing characteristics when unpowered much like
> many high performance helicopters, but more benign handling when
> powered.  The fact that this hybrid approach was determined to be
> lighter than an unpowered rotor didn't hurt.

I think the figure of merit for ease of autorotation is related to the
relative mass of the rotors vs the vehicle, where a massive rotor with a
light vehicle stores a lot of energy.  Thus tip rockets and their
propellant can make the total system mass lower, essentially by storing
energy more efficiently chemically in the propellant than kinetically in
the spinning rotor.  This costs in complexity, of course- tanstaafl.

Doug Jones
Rocket Plumber, XCOR Aerospace

From: (Bevin McKinney)
Date: 12 Feb 2001 20:07:58 GMT
Subject: Re: Rotary Scramjet? (Rotary Rocket)

>However it may still make
>sense to use LOX tank for energy storage, with compressed air being
>produced by power extracted from the rotor if possible.

If the engine designers have done their jobs right, inlet pressure requirements
will be minimal.  If the vehicle designers have matched this work by minimizing
tank weight, then you may not be able to put enough pressure in the lox tank to
be of much use.  The allowable gas pressure may be so low that cold gas
thrusters won't even run sonic at sea level.

You may be better off trading the compressor budget into added tip weight to
improve inertia in the rotor.  A couple dozen pounds can make a significant
difference if added at the rotor tip.  You really don't need all that much
power.  A few additional seconds of hover near the surface makes things a lot
easier on the pilot (meat or auto).

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