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From: Jordin Kare <>
Subject: Re: HTHL vs.VTVL ( Why a DC-X w/o wings??)
Date: 23 Jun 1996 03:39:48 GMT

In article <> Henry Spencer, writes:
>Disregarding extreme emergencies and stupidities like flying once-around
>missions from Vandenberg, the only real use of crossrange is cutting down
>the time you spend waiting in orbit for a landing opportunity.  Possibly
>the best comment on *that* came from Lt. Col. Jess Sponable at Space
>Access 96.  (For those who don't recognize the name, he was one of the
>higher-ups in the original DC-X effort, and is now at Phillips Labs
>figuring out how to test the X-33.)  His observation:  "if I have rapid
>turnaround, why do I need crossrange?".  

I found that particular comment extremely ironic, since a few years ago 
I was sitting in Jess Sponable's office at SDIO asking why the Delta
Clipper needed so much crossrange.  Even some MacDac folks admitted that
it would be much easier to do a base-first reentry, but they couldn't
meet the crossrange requirement, so a major goal (arguably *the* major
goal) of DC-X was to prove they could do the flip maneuver required by
nose-first entry and base-first landing.  [At that time, SDIO was looking
seriously at doing the whole DC-X/DC-Y/operational vehicle program on its
own, and had asked LLNL for technical comments.]

As I recall, his answer amounted to, 
"Well, it's an Air Force requirement, so we're doing it this way."

It doesn't have to make sense, it's government policy...

Jordin (Nose-first) Kare

Date: 13 Sep 1993 21:35:09 GMT
From: Jordin Kare <>
Subject: DC-X Coverage

> (Pat) writes:
>>Alright, time for everyone to fess up how they got tickets to
>>the launch.
>>Sherzer and Vanderbilt i can see through their lobbying efforts.
>>Jenks, did you use your NASA position to go as an observer?
>>how about all you others?

I went on business, as an LLNL representative, although due to 
a late decision to go I showed up on the admission list as a guest
of my boss, Lowell Wood.  My wife, Mary Kay, came too, on the grounds 
that, as she put it, "If you go to New Mexico to see the launch and 
you don't take me, you'd better _stay_ in New Mexico..."

Fortunately, Southwest Airlines had a "partners fly free" deal going,
so her airline tickets didn't cost anything.  We did have to pay
a $3 airport tax for her, however, proving once again that "There Ain't No
Such Thing As A Free Launch"

In the sole interest of making the rest of you turn green, I will also
mention that I was able to stay around after the buses took the
audience back to Las Cruces, and join the very much smaller group
that went out to the pad to look around _after_ the flight.  Very
interesting... modestly charred launch pad, modestly charred
vehicle underbody, and folks wandering around with tape measures (!)
checking the exact distance flown and things like the landing leg
lengths.  But I think they could have put it back on the stand
and launched again that afternoon.  [Oh, gee, you missed the 10 a.m. test?
Well, why don't you stick around for the 3 p.m. launch :-)]

	Jordin Kare
[Usual disclaimer:  I speak for me, not LLNL, U. California, or DOE]

Date: 14 Sep 1993 16:25:45 GMT
From: Jordin Kare <>
Subject: DC-X Mass Fractions - Different Viewpoints

In article <> (Henry Spencer) writes:

>I am put in mind of NASA's cost models... which apparently yield some
>very interesting results if you take a standard piece of lab equipment
>(the sort of thing you might want in a space-station lab), crank it
>through the models, and then compare to the off-the-shelf commercial

Just for amusement's sake, I will note that someone at the DC-X test
reported that the DC-X project (which cost ~$60M) had been run through
NASA's cost models, which projected a cost of something like $320M.
At which point a (very knowledgeable) bystander commented that NASA
must have really fudged the numbers to come up with a figure that low.

Someone else also reported a discussion with an engineer who claimed
flatly that it was impossible to build a 200 PSI pressure vessel with
a mass fraction (contents/vessel+contents) of better than 95% --
while he was holding a coke can in his hand (a coke can has a mass
fraction of about 94%, and could easily exceed 95% if it didn't have
that dimpled bottom to make it stand up).

>All too often, what these models do is institutionalize mediocrity and
>inefficiency, by predicting that future projects will do no better than
>past ones.  That appears to be what we have here.
>"Every time I inspect the mechanism     | Henry Spencer @ U of Toronto Zoology
>closely, more pieces fall off."         |  utzoo!henry

That's because the more closely you inspect, Henry, the smaller the
pieces are that you can see falling off  :-)

	Jordin Kare

Date: 4 Oct 1993 23:02:29 GMT
From: Jordin Kare <>
Subject: Kevlar tanks for DC-1

In article <> (Bruce Dunn) writes:
>> Josh Hopkins writes:
>> I have, in the past, stated that the Delta Clipper program did not use
>> materials developed from NASP.  A friend of mine brought up composite
>> cryogenic tanks as an example of something he thought had been developed
>> for  NASP and later used for DC.
>Clearly, Kevlar/expoxy
>was in the running long before NASP got started.  This isn't to say that
>MacDonnell Douglas is counting on this particular composite.  I don't really
>know what they have in mind, but Kevlar/epoxy would seem to be in the
>running.  Undoubtably, any modern tank design would take into account the 2
>decades or so of additional experience in composite materials since the
>initial tests were done.
>Bruce Dunn    Vancouver, Canada

I've just recently been involved in reviewing some DC-Y stuff.
The baseline is to use Al-Li alloy ("Weldalite") for the oxygen
tank, and carbon composite (carbon fiber in epoxy) for the LH2 tank.
The NASP program built a demonstration carbon composite LH2 tank, and
contributed significantly to the development of carbon composite tank

Kevlar- and graphite-fiber wound tanks are standard for any number of 
uses, from spacecraft to firefighter's oxygen equipment.  They have
a variety of problems, e.g., with thermal cycling inducing cracks in the 
very-highly-stressed liner, but have excellent performance overall.

BTW, DC-Y has, in theory, enough mass margin to fly with conventional AL

	Jordin (Tanks for the memories) Kare

From: Henry Spencer <>
Date: Sun, 16 Jun 1996 18:23:10 GMT

In article <4pmm1l$> (Alain Fournier) writes:
>...The way I understood
>it, the DC-X(A) were experimental vehicles and when the project
>started there was no clear intent to go on with a vehicle capable
>of reaching orbit...

Actually, it's the other way 'round.  When DC-X started, it was meant as a
precursor to the DC-Y orbital prototype, which was supposed to be flying
roughly *now* on the original fast-track schedule.  DC-Y was, in turn, to
be a precursor to a DC-1 commercial space transport, which would be
operational late in the decade.  This schedule, which was perhaps a bit
optimistic, came unravelled when political opposition began to appear. 
Particularly after the Republicans lost the White House -- SDIO having
been high on the Democrats' hit list all along -- the program's political
backing was not strong enough.  So DC-X ended up as just a technology
demonstrator, with no particular followup planned, until NASA got
interested enough to sponsor DC-XA and X-33. 
If we feared danger, mankind would never           |       Henry Spencer
go to space.                  --Ellison S. Onizuka |

From: (GCHudson)
Subject: Re: What's so brilliant...?
Date: 2 Aug 1996 20:51:23 -0400

>I was thinking about the Clipper Graham accident when a thought occured 
>to me....

I agree.  Only nose entry VTOLs, such as the DC-X vehicle Max worked on
with MDAC, have the problem with high Cg and the "topple" factor.  Base
entry vehicles with low LOX tanks such as Phoenix and the Japanese
Kan-koh-maru would not have fallen over with a single (or multiple) gear
collapse/failure to deploy.

That probaly means there wouldn't have been a fire.

From: fcrary@rintintin.Colorado.EDU (Frank Crary)
Subject: Re: non-expendable boosters and expendable fire crews
Date: 4 Aug 1996 00:17:16 GMT

In article <v02140b02ae272ccc6a46@[]>,
Simon Rowland <> wrote:
>>According to the wire service reports, they did a test flight with
>>no problems. On landing, two of the landing gear failed. The
>>vehicle fell on its side, caught fire then exploded. A program
>>manager was quoted as saying that the damage was "serious" and
>>the vehicle could not be flown again without major repairs.
>>We aren't likely to know more until later today (Thursday).
>>Apparently, there are some explosive charges on board (range safety?)
>>and they are waiting for things to cool down before approaching
>>the vehicle, rather than approach while it's still smoking and
>>get caught if one of the charges goes off.

>  That's one of tehe things I don't understand. It toppled, and the fire
>crew had 30 seconds to put the fire out before the vehilce destroyed
>itself. They opted to sit there, and hope it goes out on its own.

What fire crew? According to the wire service reports, no one
was closer than a kilometer to the landing site. (Specifically,
they said no one approached closer than that, until the day
after the accident, to avoid unnecessary risks of secondary
explosions.) For an unmanned, experimental vehicle, it doesn't
make alot of sense to have a fire crew at the landing site.

>  So now we have no flying technology testbed. Just Great.
>  The DC-XA is not expendable, but that stupid fire crew is. Send 'em in!

Well, the DC-XA _program_ certainly was expendable. It was
scheduled and funded to make four test flights, and the
accident occurred at the end of the last one (after accomplishing
most of the goals of that flight.) So your non-existent fire
crew failed to save a vehicle that wasn't going to fly
again. A tragic loss of a museum piece, but not much more.

                                                   Frank Crary
                                                   CU Boulder

From: Henry Spencer <>
Subject: Re: non-expendable boosters and expendable fire crews
Date: Sun, 4 Aug 1996 03:38:12 GMT

In article <v02140b02ae272ccc6a46@[]> (Simon Rowland) writes:
>  That's one of tehe things I don't understand. It toppled, and the fire
>crew had 30 seconds to put the fire out before the vehilce destroyed
>itself. They opted to sit there, and hope it goes out on its own.

The fire crew doesn't sit thirty seconds from the pad!  They stand back at
a relatively safe distance like sensible people.  The pad's built-in
fire-suppression system *was* activated, but wasn't enough.

>  The DC-XA is not expendable, but that stupid fire crew is. Send 'em in!

The DC-XA *was* expendable.  X-vehicles necessarily are.  The only way to
be sure you don't expend them is to leave them on the ground.  It's rather
unfortunate that DC-X's career was cut short, even rather late in its life,
but these things happen.  The people to blame are not the fire crew, but
the beancounters who limited the project to a single flight vehicle --
X-programs should build at least two, because this sort of thing happens.
 ...the truly fundamental discoveries seldom       |       Henry Spencer
occur where we have decided to look.  --B. Forman  |

From: Henry Spencer <>
Subject: Re: DC-X-A/Clipper Graham Destroyed
Date: Tue, 6 Aug 1996 14:22:02 GMT

In article <4u4t0v$> writes:
>Can the body of the craft be designed such that the corners of the
>base extend far enough that should a gear fail to deploy, the craft
>still would not topple? ...

The design of the body is constrained fairly heavily by the aerodynamics
of reentry.  With McDD's nose-first reentry, I suspect the answer is "no".
Base-first-reentry designs are often considerably wider.

As I've said before, though, making the gear deployment more reliable (in
particular, adding a backup deployment system) is likely to be far more
cost-effective than any of the more dramatic proposals.
 ...the truly fundamental discoveries seldom       |       Henry Spencer
occur where we have decided to look.  --B. Forman  |

From: Henry Spencer <>
Subject: Re: Clipper Graham blows up?
Date: Wed, 7 Aug 1996 12:27:18 GMT

In article <> (Robert I. Baumgartner) writes:
>Nonsense.  All horizontal landing machines (fighters, B-17's, airliners,
>wright flyer, etc) can do a belly landing if the landing gear either fail
>to come down, partially come down (as in the case of the DC-XA) or fail on

You're over-generalizing somewhat.  In some of them -- notably the shuttle
orbiter -- such a landing is not considered survivable.  In all of them,
it is a major emergency with a high probability of damage and injuries.

>This is why dead stick landing VTHL without fuel on board are inherently
>safer than VTVL machines which Have to have both fuel on board and rockets
>running to land...

How did we get back to this?  The topic was landing-gear failures.  (Note
that although HL vehicles seldom have redundant wings, VL vehicles do have
redundant engines, and that a dead-stick landing is considerably less fault-
tolerant than a powered landing.)

Landing gear failures are just about equally serious for the two classes
of vehicles:  either one can make a gentle touchdown in such a situation,
but both are potentially in serious trouble immediately afterward.  Note
that DC-XA's problems started not with a fire, but with a tank rupture,
and even an HL vehicle would almost certainly have its tanks pressurized
at landing (because this adds substantial structural strength).
 ...the truly fundamental discoveries seldom       |       Henry Spencer
occur where we have decided to look.  --B. Forman  |

From: Henry Spencer <>
Subject: Re: DC-XA/C.G. Fire (test #4)
Date: Tue, 20 Aug 1996 12:49:28 GMT

In article <> (Mary Shafer) writes:
>DC-X proved that you'll damage, probably destroy, the vehicle in 25%
>of the landings and seriously damage the vehicle, to the point of
>needing major repairs, in another 25% of the landings.  (Is that
>right--four flights, two that worked OK, one with major damage, and
>one with near-destruction? or did they sneak in some flights I don't
>know about? ...

It wasn't quite *that* bad, Mary.  The first test series was five flights,
the last of which damaged the aeroshell (but not the innards) extensively
as a result of problems with the ground support equipment not removing GH2
from the vicinity properly.  The second was three flights, the last of
which ended in a hard landing, cracking the aeroshell, due to altimeter
misbehavior and insufficient paranoia in the control system.  The third
was four flights, the last of which ended in DC-XA's destruction due to
landing-gear failure and tank rupture.  That's one hard landing and one
post-landing topple out of twelve flights.  (The landing on flight 5 was
perfect, despite the aeroshell being in shreds and the touchdown point
being on unpaved ground.  Even flight 12 made a perfect touchdown; the
trouble came after engine stop.)

>...The XFV-1 and XFY-1 were abandoned as
>unlandable, although they had no landings with damage.

If I'm not mistaken, their major problem was simply that it's hard to
land while looking over your shoulder; control of the aircraft was not
the issue.

>On the other hand, the X-15 program proved that rocket-powered
>vehicles could safely be landed horizontally within design limits.

Oh really?  Let's compare to DC-X.  The X-15's fourth flight involved an
in-flight fire, followed by major structural failure on landing; that's
sort of a combination of DC-X flights 5 and 8.  Then a ground engine test
nearly destroyed airframe #3; no DC-X equivalent.  Then an emergency
landing after engine failure caused landing-gear failure, with ensuing
serious airframe damage, although the aircraft was eventually rebuilt; a
reasonable analogy to DC-X flight 12.  The fatal crash arguably doesn't
count because it was probably pilot-caused, but then, DC-X didn't have
that particular failure-prone component. :-)

The X-15 *did* do considerably more flying while all this was happening...
but the X-15 had much more generous funding (three flight vehicles and a
much busier test program), considerably stronger support, and a much
tougher aircraft.

>There were no problems attributable to horizontal landings within
>aircraft limits in the entire 199-flight program...

That's like saying that the aircraft's flight history was perfect before
the crash.  X-15 flight 74 (the gear failure) would have been a minor
incident if the aircraft had been motionless at touchdown; instead it
badly injured the pilot and nearly destroyed the aircraft. 

>However, do not expect any X program to provide any information about
>operational economy.  X vehicles are technology driven and are
>unlikely to provide any useful information about operational costs or
>other operational aspects...

DC-X has provided considerable useful information about operational
economy.  X vehicles can't give definitive information on such things, but
they *can* show upper bounds.  DC-X quite effectively demolished the idea
that you need an army of people to operate a VTVL LOX/LH2 rocket vehicle.
 ...the truly fundamental discoveries seldom       |       Henry Spencer
occur where we have decided to look.  --B. Forman  |

From: (Henry Spencer)
Subject: Re: Space Access Update #91  2/7/00
Date: Thu, 10 Feb 2000 22:36:46 GMT

In article <>,
Michael P. Walsh <> wrote:
>From what I have read, both the composite LH2 tanks and the
>aluminum-lithium oxygen tank were added to the DCX-A as
>a NASA test of these tanks under flight conditions.

Correct.  When the DC-X program, as originally conceived, was more or less
over, partly because it had achieved most of its major objectives and
partly because it had run out of money and political backing, NASA took
the vehicle over as a technology demonstrator.  A number of new ideas got
put in at that point, turning DC-X into DC-XA; the tanks were just the
most visible.

>...I believe that the extra
>tank expense was not charged to the DCX program which is
>one of the reasons I am sceptical about cost comparisons
>of programs that favor the DCX...

The expense of NASA's additional goodies wasn't charged to DC-X because it
wasn't *part* of DC-X.  DC-XA was a separate program, run by a different
agency for different purposes.  Separating those costs is perfectly
legitimate, I would say.
The space program reminds me        |  Henry Spencer
of a government agency.  -Jim Baen  |      (aka

From: (Henry Spencer)
Subject: Re: SDI, help or hinderance to space development
Date: Thu, 29 Jun 2000 21:22:16 GMT

In article <>,
Tom Abbott  <> wrote:
>>>usually builds a backup vehicle in case something goes wrong with the
>>>primary vehicle.  The Clinton administration was not serious...
>>The (mistaken) decision to build only a single DC-X was made by the
>>Bush administration.
>  Can you document this?

The historical account in the Space Transportation Association's 1992
paper on SSTO vehicles -- reprinted in the summer 1992 JPAS -- is fairly
clear:  the *decision* to severely reduce the scope of the SSTO program
and turn it into SSRT, which I believe included the decision to build only
a single DC-X, was made by the Bush administration, specifically by SDIO,
more specifically by SDIO's then-director, Henry Cooper.  Congressional
funding pressure on SDIO was a factor, but so was strong interagency
pressure to keep SDIO out of the space-launch business.

> You say Bush did not request a second test vehicle, but I believe the
>reason for no second test vehicle was the democrat Congress, led by
>Senator Al Gore, would not allocate enough money for a second vehicle,
>just as in the case of the aerospace plane.

Can you document this?  Specifically the assertion that Congress
explicitly refused to fund a second vehicle?  ("Would not allocate enough
money" is nonsense if there was neither a request for it nor specific
evidence that Congress would refuse such a request; absent either of
those, what it means is that the *administration* did not give it a
sufficiently high priority within the many-billion-dollar DoD budget.)

On a related note, it's a matter of record that the evil Democratic
Congress, plus the Great Satan himself, Dan Goldin, kept DC-X alive when
the Clinton administration's DoD tried to starve it to death by sitting on
its test-operations funding.
Microsoft shouldn't be broken up.       |  Henry Spencer
It should be shut down.  -- Phil Agre   |      (aka

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