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From: Henry Spencer <>
Subject: Re: early Saturns (was Re: JPL Apollo/Mars proposal??)
Date: Thu, 30 Jan 1997 02:35:21 GMT

Further to my earlier posting, Mike Walsh sent some mail (with permission
to post it) recalling some of his experiences at the time, including:

>One of the last decisions I believe was that a four F-1 engine
>first stage would be adequate, but they wanted to go to five
>engine first stage for engine-out off-the-launch pad capability.

This wasn't mentioned in the things I've seen, but it may have been the
original motivation.  Once they started thinking about it, they discovered
that it was easy to do -- the structure was very conservatively designed
and adding a center engine was not a problem -- and it cleared up some
difficulties with exhaust recirculation into the center cavity.  The real
clincher was the margin that it added against performance problems later.

In an interview later, von Braun said "I had an awfully uneasy feeling,
you know; every time we talked to the Houston people, the damn LEM had
gotten heavier again".  When Houston-Huntsville negotiations agreed that
the Saturn V payload would be 75klb, including all margins, von Braun
quietly set the *real* Huntsville spec at 85klb, and raised it again
later.  Just as well, because Apollo 11 weighed over 90klb...

>It was my understanding they lost this, although fuel consumption
>is so high that they got the capability soon after.

According to the Saturn V Flight Manual (AS-503 edition), there were two
times when the first stage lacked engine-out capability:  the first few
seconds, and about ten seconds around max-Q.

Losing an outboard engine in the first 0.75s meant possibly hitting a
hold-down post.  Losing any engine in the first 3s meant falling back to
the pad.  Losing #1 or #2 in the first 4.5s meant a probable tower
collision.  After that, there's a period of a few seconds labelled
"possible false abort" on losing an outboard engine, in which (as best
I can make out) the rocket is actually safe but the signs can suggest

After that, everything's fine until the period between 68s and 78s, when
aerodynamic pressures are so high that losing an outboard engine can cause
structural breakup within 0.6s (!).  This was a major design driver for
the automatic abort system.  Once clear of that, there's no specific need
for an abort on losing one engine (except if you lose the only engine on
the S-IVB, of course...).

Mind you, no abort doesn't mean you can save the mission, only that there's
no need to do anything hasty.
"We don't care.  We don't have to.  You'll buy     |       Henry Spencer
whatever we ship, so why bother?  We're Microsoft."|

From: Henry Spencer <>
Subject: Re: Saturn Attitude Control
Date: Wed, 26 Mar 1997 17:36:04 GMT

In article <01bc39ac$45adafa0$9f87aec7@winbook>,
Ken Webster <> wrote:
>What mechanism was used to control/alter the attitude of the Saturn launch
>vehicle on the way up? On the older launch vehicles, you could see vernier
>jets exhausting at an angle from the booster, but I've never noticed these
>on a Saturn.

Actually, even the verniers on the Atlas were not primarily for attitude
control but for trajectory trimming after main-engine cutoff.  (They were
lit at liftoff for the same reason that Atlas used its odd 1.5-stage
concept:  at the time, there were doubts about engine ignition at high
altitude.)  They've been deleted from the latest Atlas versions.

>I assume that there was some ability for steering the thrust by adjusting
>the direction of the engines themselves?

Correct.  The Saturn V, like the Atlas, did most of its attitude control
by gimballing its main engines.  The exception was roll control in the
third stage, which only had one engine -- you need two to do roll control
by gimballing.  That was handled by a pair of little auxiliary thruster
packages, which also provided attitude control during third-stage coast,
and propellant settling before engine restart.

(Atlas likewise needed something for roll control after it dropped its
outer pair of engines.  Originally it was done by the verniers; now it
is done by a little thruster package on the interstage ring.)

>The small "fins" (or whatever they're called) at the base of
>the first stage wouldn't seem to be large enough to do much good.

They were pretty useless, in fact, and might have been removed if further
development of the Saturn V had taken place.  The one thing they were good
for was that in certain classes of nasty failure, they would reduce the
rate at which the rocket went out of control, giving the abort system a
bit more time to get the crew clear.
Committees do harm merely by existing.             |       Henry Spencer
                           -- Freeman Dyson        |

Subject: Re: Saturn V S-III Stage?
From: Henry Spencer <>
Date: Mon, 26 May 1997 04:45:13 GMT

In article <>,
Justin Wigg  <> wrote:
>Just doing some more reading and suddenly thought of something.  Why was
>the third stage of the Saturn V (and second stage of the Saturn 1B)
>called the S-IVB?  I understand that the original S-IV was on the Saturn
>1 but why wasn't the stage called the S-III? (I'm presuming sequential
>numbering: S-I (and B and C), S-II ...)

There was a lot of confusion about the upper stages for the original
Saturn.  The first attempt to definitely settle it numbered the five (!)
stages of the maximum configuration S-I through S-V.  S-I was the original
Saturn first stage, S-II through S-IV were new hydrogen stages to be
developed, and S-V was a modified Centaur.  Partly to build up hydrogen
experience gradually, and partly because S-II and S-III would need a new
big hydrogen engine, S-IV was the first of the new stages to be developed.
The original idea was to start with S-I plus S-IV (plus S-V if needed for
a particular mission), and then add S-III underneath S-IV, and then add
S-II underneath S-III.  At ill-defined points, the S-I would be replaced
by an upgraded S-IB, and then by an S-IC which would replace the eight
H-1s with a single F-1.

A bit later, NASA decided to skip the S-III and go straight to the S-II,
because it was clear that the performance requirement was rising daily.
And the S-II would go on top of an S-IC, which would have not one but two
F-1s.  Then Kennedy threw a bucket of you-know-what into the fan. :-)

Now the definitive Saturn had to get still bigger.  The S-IC spent a
little while wavering between three and four F-1s, settled on four, and
then acquired a fifth because it was easy to do and von Braun didn't trust
Houston's weight estimates for the Apollo spacecraft.  The S-II kept
growing to match.  Finally it became clear that the S-IV was too small to
make a good third stage for this monster, and NASA commissioned an S-IVB,
intended to be as nearly as possible a straight enlargement of the S-IV,
with the RL10s replaced by a single J-2.  And that's how things finally
settled out.

>Was the S-IVB to be the fourth stage of a Nova design?  (My
>understanding is that most Nova designs were still only a three stage
>vehicle with 8 F-1 engines on the first stage)

See above for details. :-) Actually, the Saturn V turned out to be as big
as a lot of the early Nova concepts.  The later Novas were a different
story; I've seen a drawing of a Nova whose first stage used five "F-6"
engines, with 7.5Mlb of thrust *each*.
Committees do harm merely by existing.             |       Henry Spencer
                           -- Freeman Dyson        |

From: Henry Spencer <>
Subject: Re: Apollo Follow-Ons
Date: Wed, 3 Jan 1996 15:24:40 GMT

In article <4cbo42$> (Magnus Redin) writes:
>>There were a number of studies of adding strap-ons to the Saturn V...
>One thing I find sad that they did not think about is the principle
>used in Arianne 4.

Well, I've always been skeptical about Ariane 4 -- it has always seemed
to me that it would be cheaper and easier to build one simple vehicle
with the maximum performance needed, and fly it with less than a full
payload at times.

It's interesting that Arianespace is doing exactly that for its next 
launcher, abandoning the Ariane 4 approach.  It's still more interesting
(since there were other reasons for Ariane 5 ending up the way it did)
that LockMart's Atlas people are doing the same thing -- condensing a
family of options into one simpler vehicle.

Besides, I think you've misunderstood the Saturn V situation.  There was
lots of work done on augmentations and strap-ons.  The error was not to
ignore the possibility of developing a range of boosters; the error was to
badly overestimate where the bottom of the range should be.  (And even
that criticism is mitigated somewhat if you look at all the work done on
"gap-filler" designs, using various pieces of Saturn hardware to try to
build a booster bigger than the Saturn IB but smaller than the Saturn V.)

>This would have made the stages less cumbersome to handle and a two
>engine core stage could more easily have found use after the moon
>program. A Saturn with 4 strapons, perhaps even with a nuclear upper
>stage would have been good for a mars mission...

This would be more or less equivalent to things that were being proposed:
tank stretches, strap-ons, nuclear upper stages.  You can't typically
go from two to four strap-ons without some redesign, not with the size
of strap-ons that would have been involved.

>This would also have
>meant a different shuttle since the need for SRB:s and extreme engine
>performance would have been gone with a two engine Saturn booster...

The problem with the Saturns was reusability, not size.  There were very
serious proposals to boost the shuttle with a derivative of the Saturn V
first stage (a single booster, not a pair).  Making it reusable cost a
little bit more than developing the SRBs, so it lost out.
Look, look, see Windows 95.  Buy, lemmings, buy!   |       Henry Spencer
Pay no attention to that cliff ahead...            |

From: Henry Spencer <>
Subject: Saturn growth (was Re: Apollo J mission LMs)
Date: Mon, 25 May 1998 16:38:20 GMT

In article <>,
Paul Michael Brown <> wrote:
>: Many changes.  The Saturn V itself was souped up slightly, by tweaking the
>: engines and deleting unnecessary bits of hardware...
>...Suppose further that during that time, lighter materials such as advanced
>alloys, composite structures and miniaturized electronics had been
>incorporated into the design. Finally, assume that the propulsion system
>had remained the same. Anybody care to hazard a guess in respect of how
>much the Saturn V's payload would have increased?

The assumptions are somewhat unrealistic, given that major improvements to
the engines had already been tested (for example, the 20%-hotter F-1A).
Furthermore, changes like new materials would not have been introduced
straight into the existing design, but would have gone into new versions
with other design changes like stretched tanks.  A Saturn V Mark 2 would
almost certainly have had uprated engines and some degree of tank stretch,
just for starters.

A more radical possibility was replacing LOX with liquid fluorine in the
second and third stages, and with a LOX/fluorine mixture in the first
stage.  (Hydrocarbon fuels need some oxygen in the oxidizer, because
fluorine doesn't cope well with the carbon content.)  NASA took this idea
quite seriously at the time, as a natural growth path.  And, of course,
there was also the idea of nuclear engines for the third stage and maybe
even the second stage (!).  (It wasn't an accident that the NERVA people
were aiming at a J-2-class engine.)

Other side issues include the possibility of a completely-redesigned and
larger third stage -- the S-IVB was too small to make a good third stage
for Earth-to-orbit, which is why it tended to be deleted from concepts
aimed at LEO heavylift work -- and strap-ons for the first stage.

Even a relatively conservative "continue existing programs but without
major new investments" plan -- the sort of thing that *just might* have
happened if the Agnew report hadn't been so totally out of touch with
political reality -- would probably have opted for engine uprating sooner
or later, since the added payload would be helpful and the new engines
were already in the pipeline.  A bit of cautious tank stretching also
seems likely.  Such a plan probably *wouldn't* have changed materials,
except in entirely new structural assemblies, which would have been few
and far between; the effort needed for redesign of existing assemblies
would not have been considered worthwhile.

All that being said, returning to the original question...

New materials and lighter subsystems in the first stage would not have
helped a lot, because the dry mass of that stage just wasn't all that
influential.  The second stage had already seen severe mass-reduction
efforts, because it was caught between a nearly-finished third stage and a
not-very-influential first stage, and had to bear the brunt of the attack
when a performance shortfall loomed.  I think the big impact would have
been in the third stage, where mass-reduction efforts hadn't been strong
due to schedule pressure, and where dead weight counted directly against
final payload.

I don't have good numbers handy for the late-model (J-mission) Saturn V
third stages, but knocking a little bit off the early ones to allow for
incremental improvements, the dry mass of the third stage was about 32klb,
and the instrument unit on top of it weighed about 4klb.  Being wildly
optimistic, say we cut the dry mass of the stage in half, and since the
IU was basically electronics, shrink it to effectively zero (it had some
structure as well, but if we don't need that to support the electronics,
we can just put the payload directly on top of the S-IVB, which we're
probably redesigning fairly drastically anyway).  That would add about
20klb to the translunar payload.  As flown, translunar payload was in the
vicinity of 100klb.  So we're talking about a substantial improvement,
but not a truly radical one.
Being the last man on the Moon                  |     Henry Spencer
is a very dubious honor. -- Gene Cernan         |

From: (Henry Spencer)
Subject: Re: Stafford & Engle
Date: Sun, 18 Oct 1998 02:39:21 GMT

In article <>,
om <> wrote:
> produce a "next generation Saturn 5". The question
>here is threefold: what original technology can be reproduced and used
>for the "Saturn 5: TNG", what would we absolutely have to build from
>scratch, and just how would the new stuff benefit from the advances in
>technology since the original S5 design was committed to blues?

Much depends on the nature of the program, and specifically on how firmly
management restrains the engineers from spending extra time and money
"improving" things.

The F-1 engine would almost certainly be revived more or less intact,
although quite possibly -- given that you've got to rebuild the tooling
and redo the qualification tests anyway -- in its souped-up F-1A form
(which was fully developed).  Engines take longer than almost everything
else, so there would be considerable advantage in sticking close to
historical precedent there.

There is an interesting question of whether you would revive the J-2
(again, probably as its fairly-well-developed J-2S derivative) or use the
SSME for the upper stages.  The SSME has better Isp, but is expensive and
manpower-intensive.  It also has about twice the thrust, which means quite
a bit of revision in the structure (for fewer engines or more total thrust
or both) on the S-II, and even bigger changes on the S-IVB.  I'd vote for
the J-2S myself; apart from the practical issues of structural changes, it
was a very versatile engine with a strong potential for other uses (e.g.,
as a heavy space maneuvering engine).

One area of where you certainly would exploit modern technology would be
that all engines on all stages would have Pogo suppressors, to kill this
problem dead rather than fumbling along case-by-case as was done on the
original Saturn V.

You might replace helium pressurization systems with propellant-boiling
systems (which were used in some places, but not everywhere), except for
S-IC kerosene pressurization.

The electronics would be done from scratch, throughout.  Reproducing the
early-1960s electronics would be costly, difficult, and pointless --
modern equivalents are better, lighter, and cheaper.  Some architectural
changes would be made too; for example, you'd make the guidance system
triple-redundant.  You might well replace mechanical and hydraulic control
systems (e.g., for tank pressurization) with electronic ones in some
places, exploiting modern electronics to make things simpler and lighter.

I've already mentioned that you'd almost certainly stretch the tanks on
the first and second stages.

It probably would not be worth messing with the first-stage structure.
On the second stage, one would think seriously about using composites in
some areas.

Any efforts for real changes would probably focus on the third stage.
That's the most performance-critical area, and it's also one where a lot
of potential for improvement existed.  Composite structures, possibly
including a composite LH2 tank and maybe even a composite LOX tank.  Maybe
use an SSME instead of a J-2/J-2S.  If you're feeling ambitious, note that
the S-IVB was generally undersized compared to the rest of the bird... so
you might follow some upgraded-Saturn proposals and build a full-diameter
third stage, the same width as the S-II, maybe even an S-II derivative.
At the very least, you'd stretch the tanks and replace various bits of
secondary structure with carbon composites.
Being the last man on the Moon is a |  Henry Spencer
very dubious honor. -- Gene Cernan  |      (aka

From: (George Herbert)
Subject: Re: The Saturn V as interplanetary truck
Date: 14 Feb 2000 17:33:42 -0800

Graham Nelson  <> wrote:
>Also, the reputation of the Saturn V as a reliable, solid piece of
>engineering derives partly from the fact that it was hardly ever
>launched -- there were very few launches, which were all made by the
>same very large and well-resourced team of people, and they were
>all successful.  But one launch, at least, was only saved by good
>luck.  It's not at all clear how reliable the Saturn system was.
>(And just imagine a Saturn V explosion on the launch pad.)

The Saturn V launcher really derives its reputation because it
was the first booster big enough to be designed with a lot of
redundancy strings and margins in some key areas.  Which it had
to use a couple of times, but successfully.  For example, most
launchers have multiple engines per stage, but are not engine out
tolerant at all... a Centaur which freezes one of its RL-10s
is SOL.  The Saturn V had either 5 engines with designed and
for the second stage demonstrated engine out capability,
or had 1 engine for the stage (which is often the best overall
solution: less engines, less can go wrong, even though it's
not failure tolerant if one happens).

Average launchers suffering that sort of failure go boom.
S-V flew to orbit with upper stage engines out on two
occations and shrugged off a lighting strike on ascent.
No other rocket I know of survived a lightning strike
nor survived engine outs on ascent, except Shuttle which
had one early shutdown on a SSME.

-george william herbert

From: (Henry Spencer)
Subject: Re: The Saturn V as interplanetary truck
Date: Tue, 15 Feb 2000 03:27:06 GMT

In article <88aadm$>,
George Herbert <> wrote:
>S-V flew to orbit with upper stage engines out on two
>occations and shrugged off a lighting strike on ascent.
>No other rocket I know of survived a lightning strike
>nor survived engine outs on ascent, except Shuttle which
>had one early shutdown on a SSME.

The Saturn I twice had first-stage engine outs during ascent.  Once was
deliberate, a demonstration of engine-out capability.  The other was an
accident -- an engine stripped its pump gears (already known to be a
marginal design, with an improved version in the works).  Both carried
on as planned.
The space program reminds me        |  Henry Spencer
of a government agency.  -Jim Baen  |      (aka

From: jscotti@LPL.Arizona.EDU (Jim Scotti)
Subject: Re: Apollo 17 LM Takeoff Video
Date: 11 Sep 2000 16:09:54 GMT

Chris Jones ( wrote:
: Michel Morton <> writes:

: > Simon Bradshaw wrote:
: > >
: > > In article <>, () wrote:
: [...]
: > >
: > > The giveaway that this is a Saturn IB S-IVB is the *three* ullage motors
: > > that fire during separation; the Saturn V S-IVB only had two.
: >
: > That sound's curious, I'd have thought it would be the other
: > way round as the added weight of the LM would mean the Saturn
: > V would use 3 to provide enough acceleration to settle the S-IVB
: > propellants.
: >
: > Of course I'm assuming they're identical. Could it be the S-IB
: > used 3 smaller ones and the Saturn V used 2 larger ones? That would
: > make sense if the motors where off the shelf items.

: I don't know if it's the case here, but the Saturn V tended to lose
: retrorockets and ullage motors as time went on, as experience showed exactly
: what was needed.

I'm sure that is the case here - early flight experience showed that 3
weren't necessary, so to save weight in the Saturn V and add weight into
the Apollo spacecraft and equipment, they trimmed the excess off of
this magnificent vehicle.  The German engineering was notoriously
conservative in the design of the Saturn V, so when the MSC people
came into meetings asking about extra payload capacity for their growing
Apollo spacecraft, Von Braun's people looked like Mr. Scott, the miracle
worker of the starship Enterprise, giving them much of what they asked
for by trimming some of the margin, or stretching the capability of the
overengineered components slightly (a little extra thrust here, one or
two less ullage rockets there...).  As the Saturn V model on my desk
demonstrates, the 1st/2nd interstage originally had 8 seperation motors
on it.  I think it flew with only 4 through most or even all of the Apollo
flights (I forgot to check on that detail when I built it - I wanted a
flight accurate model and that's one place I goofed).


Jim Scotti
Lunar & Planetary Laboratory
University of Arizona
Tucson, AZ 85721 USA       

From: (Henry Spencer)
Subject: Re: Apollo 17 LM Takeoff Video
Date: Tue, 12 Sep 2000 02:39:39 GMT

In article <8pj04i$j9g$>,
Jim Scotti <jscotti@LPL.Arizona.EDU> wrote:
>...As the Saturn V model on my desk
>demonstrates, the 1st/2nd interstage originally had 8 seperation motors
>on it.  I think it flew with only 4 through most or even all of the Apollo
>flights ...

Apollo 15 and after in fact had *no* ullage motors on the interstage ring;
they were deleted as unnecessary.

(Apollo 15 also tried deleting four of the eight first-stage retros, but
staging separation wasn't as quick as predicted -- the F-1 engine thrust
tailed off more slowly than expected -- and analysis indicated that if one
retro had failed to ignite, the two stages might have collided after
separation.  So they put the extra first-stage retros back.)
Microsoft shouldn't be broken up.       |  Henry Spencer
It should be shut down.  -- Phil Agre   |      (aka

From: (Henry Spencer)
Subject: Re: Manned V2 -- Pictures
Date: Fri, 27 Oct 2000 16:13:48 GMT

In article <wU7K5.1672$>,
Doug... <> wrote:
>It always tickled me a little bit, though, that the Saturn 5 did, indeed,
>have fins.  Hard to say how much they were actually needed... anyone have
>any actual test data to indicate just how much the fins were needed?

I've heard two different stories on that, from people who were there:

1. "The fins were not needed in normal flight, but did slow down loss of
control in certain failure cases, giving the abort system more time."

2. "The fins were pure superstition and did nothing useful whatsoever; we
tried to talk Marshall into removing them, and would have tried again if
Saturn V production had continued."
Microsoft shouldn't be broken up.       |  Henry Spencer
It should be shut down.  -- Phil Agre   |      (aka

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