Thomas Frieling in Spaceflight

[Michael Gallagher]

[carbon copy of this message being e-mailed to the man himself]

Hi, All..

Saw Thomas Frieling's piece in Spaceflight. Very nice!

No strong feelings either way on whether the shuttle should be ultimately
replaced by either a manned capsule or a small spaceplane, but this brings
up a question I've had in mind for a long time:

Would it be possible to build a reusable CAPSULE? Obviously, it would be
launched on an ELV and still have a disposable SM, but why not build a
series of capsules that can be used repeatedly and save a little money? The
reusability concept must have some validity to it!

Have a good one.

[Derek Lyons]

"Michael Gallagher" > wrote:
>Would it be possible to build a reusable CAPSULE?

Certainly.

>Obviously, it would be launched on an ELV and still have a disposable SM,

And why are these obvious?

>but why not build a series of capsules that can be used repeatedly and save
>a little money?

Much depends on how much refurbishment is required between flights.
The big expense in reflight is all of the integration and testing.


>The reusability concept must have some validity to it!

The problem is, the less you re-use, the less you save. Somewhere
along the spectrum between "full re-use" and "zero re-use" is the
balance point, but that point can shift with technology, engineering
tradeoffs, etc... for any given application.

D.
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[LooseChanj]

On or about Sat, 09 Aug 2003 18:54:25 GMT, Brian Thorn >
made the sensational claim that:
> I think it would probably make more sense to go the wings or lifting
> body route if reusability were your prime concern. Then you'd have the
> SM functions in the same airframe and can reuse the whole shebang.

Or you could design the SM functions into the same capsule. I don't see
where wings would have anything to do with reusability.
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[Phil A. Buster]

"Michael Gallagher" > wrote in message
...
> [carbon copy of this message being e-mailed to the man himself]
>
> Hi, All..
>
> Saw Thomas Frieling's piece in Spaceflight. Very nice!
>
> No strong feelings either way on whether the shuttle should be ultimately
> replaced by either a manned capsule or a small spaceplane, but this brings
> up a question I've had in mind for a long time:
>
> Would it be possible to build a reusable CAPSULE? Obviously, it would be
> launched on an ELV and still have a disposable SM, but why not build a
> series of capsules that can be used repeatedly and save a little money?
The
> reusability concept must have some validity to it!
>

It is certainly possible. The bigger question is whether it is cost
effective. According to a number of articles I've seen over the years, NASA
found that returned Apollo capsules were in surprisingly good condition, and
actually did give some thought to reuse. It was not pursued because of the
limited scope of the program and the adequate number of capsules
manufactured and available at the time. I have occasionally wondered if
Russia reuses any Soyuz components. They don't as far as I know, but I
have never seen it discussed one way or the other. One would think that a
certain amount of hardware (e.g. radios and the like) should be readily
reusable, regardless of the bigger issue of the capsule itself.

[gmw]

Would it be possible to build a reusable CAPSULE? Obviously, it would be
launched on an ELV and still have a disposable SM, but why not build a
series of capsules that can be used repeatedly and save a little money?

Yes. During the transition period from shuttle to OSP the capsule and/or
service module can be brought back by a later shuttle flight. This would
require the item to be returned, most probably just the service module, to
be placed in a parking orbit accessible by the shuttle after the shuttle has
completed it primary mission.

Once the shuttle is retired a shuttle free reusable capsule is also
possible. If memory serves the Apollo capsules were intended to be
reusable, they were to "thump" down on land and be refurbished. Again, I
ma working from memory, each Apollo capsule could have bee flown up to five
times. Political posturing about whose congressional district the returning
heroes would thump down in led to NASA to switch to a water landing.
Strongly, being heated to several thousand degrees before taking a sal****er
dunk did nothing for the capsules reusability.

One of the primary arguments against a capsule is the need to mount a full
scale search and rescue effort every time one lands. The Navy billed NASA
through the noose for the use of its vessels and people. But, I have also
seen drawing and notes for a controlled landing by an advance Gemini capsule
using a fabric based, hang glider like Rollo wing. Putting the two together
and a reusable capsule is a very doable and much less expensive than many
make it out to be.

[Brian Thorn]

On Sat, 09 Aug 2003 20:06:28 GMT, LooseChanj >
wrote:

>On or about Sat, 09 Aug 2003 18:54:25 GMT, Brian Thorn >
>made the sensational claim that:
>> I think it would probably make more sense to go the wings or lifting
>> body route if reusability were your prime concern. Then you'd have the
>> SM functions in the same airframe and can reuse the whole shebang.
>
>Or you could design the SM functions into the same capsule. I don't see
>where wings would have anything to do with reusability.

If you can figure out how to do it that way, I'd be all for it, but I
think a CM/SM one-airframe design is going to be so complicated you
may just as well go whole hog and make it a runway lander. From a
practical point of view, I think an X-20/HL-20-type airframe lends
itself much more to reusable service components than an Apollo or
Soyuz-like capsule does.

Brian

[Derek Lyons]

"gmw" > wrote:
>Once the shuttle is retired a shuttle free reusable capsule is also
>possible. If memory serves the Apollo capsules were intended to be
>reusable, they were to "thump" down on land and be refurbished.

Your memory fails. Gemini briefly was intended to come down on land
(under a parawing), but Apollo was targeted for a water landing from
the start.

>Again, I ma working from memory, each Apollo capsule could have bee
>flown up to five times. Political posturing about whose congressional district
>the returning heroes would thump down in led to NASA to switch to a water landing.

Your memory fails. There never was any such thing considered.

>Strongly, being heated to several thousand degrees before taking a sal****er
>dunk did nothing for the capsules reusability.

Your knowledge fails. The interior of the capsule is exposed to
neither great heat, nor sal****er. The heatshield, which is so
exposed, would have to be replaced each time regardless of landing
mode.

>One of the primary arguments against a capsule is the need to mount a full
>scale search and rescue effort every time one lands.

Your knowledge fails. With few exceptions the capsules came down in
the intended area, and neither search nor rescue was required.

>But, I have also seen drawing and notes for a controlled landing by an advance
>Gemini capsule using a fabric based, hang glider like Rollo wing.

Your knowledge fails. That's the original intended landing mode for
Gemini, but the parawing was canceled when it had severe developmental
problems.

>Putting the two together and a reusable capsule is a very doable
>and much less expensive than many make it out to be.

That's an opinion, and a very debatable one at that.

D.
--
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[Brian Thorn]

On Sat, 09 Aug 2003 13:21:11 -0700, Eddie Valiant
> wrote:

>>I think it would probably make more sense to go the wings or lifting
>>body route if reusability were your prime concern. Then you'd have the
>>SM functions in the same airframe and can reuse the whole shebang.
>
>And just to open a line of discussion, what would be the need for a
>winged/lifting body concept over a capsule design?

Weight, for one. A crew module descent under parachutes is one thing.
Trying to bring the mass of the entire CM/SM down under chutes,
well... you can volunteer to be the first passenger! Now, a DC-X-like
design with powered vertical landing could work, too, but that also is
fairly far removed from the capsule concept, and we have a lot more
experience with wings and lifting bodies.

>What does one do
>over the other that would make it preferable? To my way of thinking,
>the capsule would be the route to go since there's really no need
>[that I can see] to carry large payloads up with a manned crew ala the
>space shuttle.

I wasn't talking about the payload, I'm talking about the orbital
maneuvering system, power, long-duration life support, and fuel that
the Service Module carries. They're heavy and expensive, and they're
thrown away with all of the capsule concepts, and even some of the
wing/lifting body concepts.

I'd like to see the SM be reusable, too. Perhaps the design for the
OSP should have a universal cargo arear, where on some missions, the
"cargo" is actually a crew compartment. On other missions, it's an
MPLM or ATV-like cargo module. That way, we get full reusability of
the manned spacecraft, the cargo carrier, and the service module.

Brian

[OM]

On Sat, 09 Aug 2003 22:34:10 GMT, (Derek Lyons)
wrote:

>Your knowledge fails.

....CT's Syndrome, first stage.

>That's the original intended landing mode for Gemini, but the parawing
>was canceled when it had severe developmental problems.

....Most, if not all of those problems were in deploying the wing from
its stored state between the hatches. Deployed, the Rogallo Wing
worked pretty much as advertised.

OM

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[Derek Lyons]

OM <om@our_blessed_lady_mary_of_the_holy_NASA_research _facility.org>
wrote:

>On Sat, 09 Aug 2003 22:34:10 GMT, (Derek Lyons)
>wrote:
>
>>That's the original intended landing mode for Gemini, but the parawing
>>was canceled when it had severe developmental problems.
>
>...Most, if not all of those problems were in deploying the wing from
>its stored state between the hatches. Deployed, the Rogallo Wing
>worked pretty much as advertised.

That pretty much counts as developmental problems in my book... No
matter how wonderful the Rogallo performed, it's of little use if you
cannot deploy it.

Anyone know if there has been any further work?

D.
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[gmw]

Your memory fails. There never was any such thing considered.


Damm! How did I get so old?

[David Higgins]

gmw wrote:
> Damm! How did I get so old?

Time.

[Peter Stickney]

In article >,
(Derek Lyons) writes:
> LooseChanj > wrote:
>
>>On or about Sat, 09 Aug 2003 18:54:25 GMT, Brian Thorn >
>>made the sensational claim that:
>>> I think it would probably make more sense to go the wings or lifting
>>> body route if reusability were your prime concern. Then you'd have the
>>> SM functions in the same airframe and can reuse the whole shebang.
>>
>>Or you could design the SM functions into the same capsule. I don't see
>>where wings would have anything to do with reusability.
>
> Wings, or a lifting body, or Roton's blades, all allow for greater
> crossrange and more predictable and precise targeting of the landing
> point.
>
> This has a lot to do with reusability and routine operations.

And cost. What's the point of building a reusable capsule if, in
order to deal with the need for a water landing, you need to keep the
equivalent of a Carrier Battlegroup on watch during a flight.

Yes, I know that if you were shooting for a reusable capsule, you;d
prefer it to land on land, but, no matter what you use it for - either
standalone space flights, or as a station CRV lifeboat, there's a
strong probability, epxecially if you're going to make a lot of
flights, that you;ll have to make unscheduled landings, and ballistic,
or semi-ballistic capsules don't hve a lot of landing footprint after
the retro burn takes place. One of the lucky things about the
Mercury/Gemeni/Apollo era, for the U.S., was that we had a large
number of Antisubmarine Carriers, and their support groups, whose
entire mission was searching for small objects in the Ocean. They
were the logical primary recovery assets for the U.S. capsule
missions. Their operation costs (not cheap by any means) also came
out of the Navy budget - If they weren't working as spacecraft
recovery forces, they'd be doing something else, so it wasn't an added
cost in that case. But they're all gone now. In fact, they've been
gone for more than 30 years. Even the U.S.N. doesn't have the number
of ships that it would take (And it _will_ take a Carrier of some sort
- the only way you can get the search coverage you need is with
aircraft, lots of aircraft.) You can't count on precision location.
Such things can be counted on to fall short when you need them.
And no, there aren't any other assets that would apply. The USAF has
about a half-dozen Rescue Squadrons, which are, with the exception of
the units tasked to cover Cape Canaveral, and Shuttle launches, pretty
much solely geared to short-range Combat SAR. The Coast Guard has no
spare assets whatsoever, and since the retirement of the HH-3F
Pelicans, no long range recovery assets.

Oceans are big places, and it matters not one bit if you lose a crew
to a re-entry failure, or the perish at sea waiting for rescue.

If you're going to be flying into space on a regular basis, reusable
or not, you're going to need a spacecraft concept that can make a safe
landing from anywhere. The Shuttle does this with wings & landing
gear, but it doesn't have to be that way. I like the concept of the
X-38 prototype, myself - build a shape optimized for high speed
flight, and let the landing phase be performed under a parawing. That
keeps teh number of "sticky-out bits" to a minumum, and gives the best
landing options.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster

[LooseChanj]

On or about Sun, 10 Aug 2003 15:21:41 -0400, Peter Stickney
> made the sensational claim that:
> And cost. What's the point of building a reusable capsule if, in
> order to deal with the need for a water landing, you need to keep the
> equivalent of a Carrier Battlegroup on watch during a flight.

Do you? A capsule doesn't mean everything has to be done just as Apollo
was.

> If you're going to be flying into space on a regular basis, reusable
> or not, you're going to need a spacecraft concept that can make a safe
> landing from anywhere. The Shuttle does this with wings & landing
> gear, but it doesn't have to be that way. I like the concept of the
> X-38 prototype, myself - build a shape optimized for high speed
> flight, and let the landing phase be performed under a parawing. That
> keeps teh number of "sticky-out bits" to a minumum, and gives the best
> landing options.

And precludes the use of a capsule how?
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[George William Herbert]

Brian Thorn > wrote:
>"Michael Gallagher" > wrote:
>>Would it be possible to build a reusable CAPSULE? Obviously, it would be
>>launched on an ELV and still have a disposable SM, but why not build a
>>series of capsules that can be used repeatedly and save a little money? The
>>reusability concept must have some validity to it!
>
>I think it would probably make more sense to go the wings or lifting
>body route if reusability were your prime concern. Then you'd have the
>SM functions in the same airframe and can reuse the whole shebang.

[This is lousy terminology, by the way, but I will approach that
problem later...]

Why would you not put the 'SM functions' inside the main capsule
if you are designing a capsule for reusability?

The reasons to put them outside are to minimize the re-entry TPS
and recovery systems mass, in a non-reusable system. If you are
going to reuse those systems, the mass multipliers for TPS and
for recovery are the same if you have CM or CM+SM functions in
the one capsule, or if you have CM+SM functions in one winged
or lifting body vehicle.


-george william herbert

[George William Herbert]

Brian Thorn > wrote:
>But isn't there a point where your spacecraft is just getting too big
>to land under parachutes? X-38 already had the largest airfoil ever
>flown, and it was still small compared to the conventional wisdom on
>OSP designs.

X-38 had the largest parafoil I am aware of being made or tested.
But very large parachute clusters have been used repeatedly and
successfully in the past. The Army has airdropped stuff in that
size range for decades and decades.

And keep in mind... a capsule is going to be lighter for the same
capabilities, as it doesn't have all those dead weight wings etc.


-george william herbert

[Michael Gallagher]

On Sat, 09 Aug 2003 21:12:38 GMT, "gmw" > wrote:

> ..... I have also
>seen drawing and notes for a controlled landing by an advance Gemini capsule
>using a fabric based, hang glider like Rollo wing. Putting the two together
>and a reusable capsule is a very doable and much less expensive than many
>make it out to be.
>
Tom's article proposes that a revived CM would make a land landing
somewhere in the US southwest, cushioned by either retro rockets or
air bags. That should take care of the salt water problem!



>

[Michael Gallagher]

On Sat, 09 Aug 2003 18:54:25 GMT, Brian Thorn >
wrote:

>I think it would probably make more sense to go the wings or lifting
>body route if reusability were your prime concern. Then you'd have the
>SM functions in the same airframe and can reuse the whole shebang.
>

True. The point is if TPTB decide in the end to go for a capsule,
could it be resuable?

[jeff findley]

Brian Thorn > writes:
> Instead, it will have to have a honkin' big parachute/airfoil which
> had better deploy just right. Even then, you might still need a retro
> rocket to make landing bearable for the crew.
>
> And how big a capsule can they fit on top of a Delta or Atlas before
> they start getting into aerodynamic problems that make wings look
> easy?

Capsules are still easier to launch on ELVs than anything with wings.
Their axisymmetric shape makes the aerodynamics much easier, even if
you have to resort to a "hammer head" design.

Every model rocket designer knows that you don't want to add large
aerodynamic surfaces at the nose of a rocket. I wonder why "real"
aerospace engineers often gloss over this issue when they propose
mounting anything with wings on an ELV. It really is a complex issue
that shouldn't be glossed over, yet how many "pretty pictures" have we
seen of an X-38 style CRV on top of a Delta IV or an Atlas V?

Still, Delta IV looks to be 5m diameter, which is larger than the
Apollo CSM's 3.90m diameter, and this is before you start talking
about "hammer head" shapes. Atlas V has a mild "hammer head" payload
fairing in order to achieve the same 5m diameter payload fairing. In
traditional US units, this is about 16.4 ft in diameter. That's a
pretty large capsule. I'll bet you could fit quite a few standard ISS
payload racks in a capsule this size.

Jeff
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[George William Herbert]

Brian Thorn > wrote:
(George William Herbert) wrote:
>>And keep in mind... a capsule is going to be lighter for the same
>>capabilities, as it doesn't have all those dead weight wings etc.
>
>Instead, it will have to have a honkin' big parachute/airfoil which
>had better deploy just right. Even then, you might still need a retro
>rocket to make landing bearable for the crew.

Retro rocket, or moderate crush space in the seat mounts, etc.

>And how big a capsule can they fit on top of a Delta or Atlas before
>they start getting into aerodynamic problems that make wings look
>easy?

Both Atlas V and Delta IV are qualifying with 5m shrouds.
So at least that big. There has been open speculation of
a 7m shroud to fit a winged OSP under while avoiding the
wing lift loads problem, so someone is thinking of that
sized hammerhead on both vehicles. A large hammerhead is
more drag, and more shroud weight, but is not an unmanageable
problem by any means.

A 5m capsule is plenty big for the OSP mission...


-george william herbert

[Brian Thorn]

On 11 Aug 2003 16:16:33 -0400, jeff findley
> wrote:


>Still, Delta IV looks to be 5m diameter, which is larger than the
>Apollo CSM's 3.90m diameter, and this is before you start talking
>about "hammer head" shapes. Atlas V has a mild "hammer head" payload
>fairing in order to achieve the same 5m diameter payload fairing. In
>traditional US units, this is about 16.4 ft in diameter. That's a
>pretty large capsule. I'll bet you could fit quite a few standard ISS
>payload racks in a capsule this size.

But not the payload racks and the Service Module.

Brian

[Brian Thorn]

On Sun, 10 Aug 2003 15:21:41 -0400, (Peter
Stickney) wrote:

>> This has a lot to do with reusability and routine operations.
>
>And cost. What's the point of building a reusable capsule if, in
>order to deal with the need for a water landing, you need to keep the
>equivalent of a Carrier Battlegroup on watch during a flight.

You don't. The greatest "miss distance" of an operational Apollo
splashdown was something like 5 miles, and that was unusual: most were
within a mile, well within sight of the carrier.

You could aim for routine splashdowns off the Cape, recovered by the
SRB recovery ships. In an emergency, you could aim for just outside
pretty much any major seaport.

Brian

[George William Herbert]

Brian Thorn > wrote:
> wrote:
>>Still, Delta IV looks to be 5m diameter, which is larger than the
>>Apollo CSM's 3.90m diameter, and this is before you start talking
>>about "hammer head" shapes. Atlas V has a mild "hammer head" payload
>>fairing in order to achieve the same 5m diameter payload fairing. In
>>traditional US units, this is about 16.4 ft in diameter. That's a
>>pretty large capsule. I'll bet you could fit quite a few standard ISS
>>payload racks in a capsule this size.
>
>But not the payload racks and the Service Module.

What service module are you referring to here?


-george william herbert

[George William Herbert]

Brian Thorn > wrote:
(George William Herbert) wrote:
>>>>I'll bet you could fit quite a few standard ISS
>>>>payload racks in a capsule this size.
>>>
>>>But not the payload racks and the Service Module.
>>
>>What service module are you referring to here?
>
>The propulsion and power systems to get the racks to and from the
>Space Station. Even if this requires only half the mass of the Apollo
>SM (and I think that's a realistic ballpark figure), we're still
>talking two or three times the mass of the CM alone. All in a capsule
>only a couple of feet greater in diameter than Apollo.

Several feet greater in diameter, but I digress.

I recommend to you a bit of directed research:
go through the manned capsules section of Mark Wade's
site looking at the delta-V of space station logistics
vehicles real and proposed, and figure out their mass
ratios and fuel fractions. The best bets are to look
at the numbers for the various Soyuz models and the
British Aerospace Multi-Role Capsule.

"2-3 times the mass of the CM alone" is a gross, gross
overestimate. Small multiplier. Really.

>I have no objection to a large capsule used for crew and cargo
>transport. It's the proposal that the crew (or cargo) AND the service
>systems (propulsion, life support -- more than a few hours worth --
>and electrical power) can be all compressed into a 15-ft diameter
>capsule that I have difficulty accepting. My argument is that if we
>want to reuse the service systems in addition to the crew cabin, then
>the capsule is less suited for it than a winged or lifting-body shape.

Look at all the MRC was able to compress into a single 4 meter capsule.

Work out the numbers on required delta-V, mass ratio, etc.

Design a few capsules, on a notepad. Just sketch them
to get an idea of volumetric requirements for people,
systems, fuel tanks, etc.

You can do a lot in 5 meters (16.4 feet).
Plenty, if your mission is OSP. Even the "7-8 passengers up
and down and/or lotsa racks" jumbo version.


-george william herbert

[jeff findley]

Brian Thorn > writes:
>
> The propulsion and power systems to get the racks to and from the
> Space Station. Even if this requires only half the mass of the Apollo
> SM (and I think that's a realistic ballpark figure), we're still
> talking two or three times the mass of the CM alone. All in a capsule
> only a couple of feet greater in diameter than Apollo.

You're being grossly mislead by a system designed for lunar travel.
The Apollo SM was grossly oversized for LEO missions. As such, you're
comparing apples and oranges. For reasonable sized service modules, I
suggest you look at vehicles (existing and proposed) that serve this
role in LEO.

I'd look at the delta-V of Progress, Soyuz, ATV, HTV, and the like.
You'll be pleasantly surprised that these don't require nearly the
delta-V needed to brake (the CSM and LM) into lunar orbit and later
put the CSM on an earth return trajectory.

> I have no objection to a large capsule used for crew and cargo
> transport. It's the proposal that the crew (or cargo) AND the
> service systems (propulsion, life support -- more than a few hours
> worth -- and electrical power) can be all compressed into a 15-ft
> diameter capsule that I have difficulty accepting. My argument is
> that if we want to reuse the service systems in addition to the crew
> cabin, then the capsule is less suited for it than a winged or
> lifting-body shape.

Where did you get 15 feet? You've got a 16.4 foot diameter limit, if
you're talking about using Delta IV or Atlas V as your launch vehicle.
That extra 1.4 feet buys you quite a bit of extra volume, since it
also lets the capsule be longer and still maintain an Apollo CM shape.

If you grossly simplify the problem as a cube, you see:

16.4ft ^ 3 = 4411ft^3
15ft ^ 3 = 3375ft^3

So that extra 1.4 feet of length increases your volume by nearly 1/3
of the smaller volume. I'll bet your LEO specified replacement SM
equipment will fit in that space.

> Whether we should try to reuse the service systems is another matter.
> But I think if we're going to aim for eventual reusability of the
> command module, we should instead aim from the beginning for complete
> reusability... command and service module... with an airframe designed
> for it from the start.

No doubt. However, the devil in the details isn't as bad as you
suspect. We're trying to reuse the shape of the Apollo CM, the SM is
largely irrelevant. The systems the SM contains ought to be replaced
with more modern systems anyway. Especially the propulsion system,
where I'd want to get away from toxic propellants and switch to
something a bit more benign.

Jeff
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[Brian Thorn]

On 12 Aug 2003 11:17:40 -0400, jeff findley
> wrote:

>> The propulsion and power systems to get the racks to and from the
>> Space Station. Even if this requires only half the mass of the Apollo
>> SM (and I think that's a realistic ballpark figure), we're still
>> talking two or three times the mass of the CM alone. All in a capsule
>> only a couple of feet greater in diameter than Apollo.
>
>You're being grossly mislead by a system designed for lunar travel.

No, I'm not. Apollo was not designed for lunar travel, it was designed
as NASA's all-purpose manned spacecraft to succeed Mercury. The moon
mission came later.

That said, I am grossly overestimating its mass. Empty, the SM weighed
about 20,000 lbs., far less than I had thought. And that's about twice
as much as is needed for the LEO mission.

Remember that one of OSP's requirements is for greater maneuverability
than Shuttle. That's going to drive prop requirements significantly
higher.

>> I have no objection to a large capsule used for crew and cargo
>> transport. It's the proposal that the crew (or cargo) AND the
>> service systems (propulsion, life support -- more than a few hours
>> worth -- and electrical power) can be all compressed into a 15-ft
>> diameter capsule that I have difficulty accepting. My argument is
>> that if we want to reuse the service systems in addition to the crew
>> cabin, then the capsule is less suited for it than a winged or
>> lifting-body shape.
>
>Where did you get 15 feet?

Lifeboat mode, to be launched aboard Shuttle. Unless we decide on two
variants (driving up costs) were stuck with 15 feet max.

Brian

[Derek Lyons]

Brian Thorn > wrote:

>On 12 Aug 2003 11:17:40 -0400, jeff findley
> wrote:
>
>>> The propulsion and power systems to get the racks to and from the
>>> Space Station. Even if this requires only half the mass of the Apollo
>>> SM (and I think that's a realistic ballpark figure), we're still
>>> talking two or three times the mass of the CM alone. All in a capsule
>>> only a couple of feet greater in diameter than Apollo.
>>
>>You're being grossly mislead by a system designed for lunar travel.
>
>No, I'm not. Apollo was not designed for lunar travel, it was designed
>as NASA's all-purpose manned spacecraft to succeed Mercury. The moon
>mission came later.

Yes you are. Apollo was *intended* as a general purpose orbiter, but
it's design was hardly begun before it's mission, and design, were
shifted to being the command craft for the lunar mission.

D.
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[Thomas J. Frieling]

Well since I wrote the op-ed piece I'll add to this discussion.

1) Yes you can reuse Apollo type Command Modules.

Remember NASA launched Gemini 2, then gave it to the USAF who carved a
hatch in its heat shield, then re-launched it on the first and only
MOL flight. It was recovered in good shape and I believe is still on
display at the USAF Museum at the Cape.

But do you want to reuse the CM? I doubt it. For one thing if you, by
some miracle, got Congress to fund Apollo Redux, the contractor will
build five or ten, then shut the production line down. Then you start
losing them over time and you're in the same state NASA is in today
after losing 40% of its Shuttle fleet in two decades of flight: the
other side of the coin of reusability is "losability." Much better to
have the production lines open.

If NASA keeps flying Shuttles, some day they will run out of Shuttles.
Russia, on the other hand, just keeps building Soyuzes. We should have
followed their model: Even though they built a Shuttle, they never
discarded their Soyuz technology. If the US had kept Apollo CSM/Saturn
1B technology, we'd be a lot better off today than we are, waiting for
the Shuttle to return to flight.

Is it cost effective to reuse a CM? Who knows? But note that NASA goes
to a lot of trouble to recover and reuse the Shuttle SRBs even though
studies have determined it would be cheaper to throw them away.

I submit that NASA is chasing a chimera with reusability and would be
better off if it gave up on that notion.

2) You don't need Carrier Task Groups deployed for contingency
landings Even if your flying an Apollo type CSM. Does Russia deploy
Naval vessels for Soyuz? Heck no. You solve the contingency landing
zone problem by giving the craft sufficient on-orbit loiter time to
hit any landing zone. I prefer Kansas, or Edwards, but you also have
the vast steppes of Russia (where more than a few manned missions have
ended, right?) or even the Australian Outback if you needed it.

3) And you don't even need all that much open space. Apollo did have
some, albeit modest, cross range capability, since its center of
gravity was offset. Enough to avoid bad terrain on landing is all you
need. Plus, Apollo landings were very accurate. So land landings are
not a particular challenge.

4) Proponets of OSP "wings and wheels" approaches like to tout the
gentle low g reentry, supposedly so injured crewman will not suffer
adverse effects. But Apollo LEO reentries only pulled a little more
than three Gs max. I submit if a cremember is too ill to manage 3 gs,
he probably is beyond help.

And the one major advantage of reviving the manufacture of Apollo CM
vehicles is it opens the possibility of going back to the moon. You'll
never be able to justify the payload hit you'd suffer by hauling wings
and wheels all the way to the moon where they are of absolutely no
use. But once again having a CSM, you could at least entertain the
notion of going back.

Bottom line is: The next Shuttle disaster will be the last one. I am
sure the political fallout of losing another orbiter will surely end
the program.

So does NASA roll the dice every time it flies a Shuttle, hoping it
will return in one piece? Or does it get on with the task of replacing
it? If NASA does lose another Shuttle before a replacement is
operational, it will likely mean the end of US manned spaceflight.

As I said in the op-ed piece: Use the Shuttles to finish Space
Station construction, then retire the fleet. An updated Apollo CSM
then takes over crew rotation and an unmanned cargo carrier--a Jumbo
Progress vehicle--takes over logistics for resupply.

Then back to the moon....

"Phil A. Buster" > wrote in message >...
> "Michael Gallagher" > wrote in message
> ...
> > [carbon copy of this message being e-mailed to the man himself]
> >
> > Hi, All..
> >
> > Saw Thomas Frieling's piece in Spaceflight. Very nice!
> >
> > No strong feelings either way on whether the shuttle should be ultimately
> > replaced by either a manned capsule or a small spaceplane, but this brings
> > up a question I've had in mind for a long time:
> >
> > Would it be possible to build a reusable CAPSULE? Obviously, it would be
> > launched on an ELV and still have a disposable SM, but why not build a
> > series of capsules that can be used repeatedly and save a little money?
> The
> > reusability concept must have some validity to it!
> >
>
> It is certainly possible. The bigger question is whether it is cost
> effective. According to a number of articles I've seen over the years, NASA
> found that returned Apollo capsules were in surprisingly good condition, and
> actually did give some thought to reuse. It was not pursued because of the
> limited scope of the program and the adequate number of capsules
> manufactured and available at the time. I have occasionally wondered if
> Russia reuses any Soyuz components. They don't as far as I know, but I
> have never seen it discussed one way or the other. One would think that a
> certain amount of hardware (e.g. radios and the like) should be readily
> reusable, regardless of the bigger issue of the capsule itself.

[jeff findley]

(Derek Lyons) writes:
>
> Yes you are. Apollo was *intended* as a general purpose orbiter, but
> it's design was hardly begun before it's mission, and design, were
> shifted to being the command craft for the lunar mission.

Especially the SM. As I said, the SM is grossly oversized for the
types of LEO missions that NASA needs to perform.

http://www.astronautix.com/craft/apolocsm.htm

The SM's propellant load was 18,413 kg while its overall mass was
24,523 kg. The maneuver system delta v was 2,804 m/s. To most, this
figure may be meaningless, so for comparison, let's look at the
shuttle:

http://www.astronautix.com/craft/endavour.htm

Endeavour's delta v is listed as 700 m/s. That puts the CSM's delta v
at 4x that of the shuttle. I'm not sure what orbit insertion costs in
terms of delta v, but that's a figure one could arguably charge
against the "launch vehicle", which you won't have for a CRV/CTV if
you assume that the launch vehicle puts it completely in orbit.

http://www.astronautix.com/craft/soyuztma.htm

One more data point. The Soyuz TMA has a listed delta v of 390 m/s,
which is a bit more than 1/2 that of Endeavour and less than 1/7 that
of the Apollo CSM.

Jeff
--
Remove "no" and "spam" from email address to reply.
If it says "This is not spam!", it's surely a lie.

[Derek Lyons]

jeff findley > wrote:
>One more data point. The Soyuz TMA has a listed delta v of 390 m/s,
>which is a bit more than 1/2 that of Endeavour and less than 1/7 that
>of the Apollo CSM.

That may be a product of Soyuz's role as a dedicated taxi as opposed
to the Shuttle's partial role as a general purpose orbiter. The
Shuttle's listed delta-V may be misleading if it's at the orbiters
empty weight. Unlike Soyuz and Apollo, the Shuttle's payload varies
greatly and is an appreciable fraction of the total mass.

D.
--
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[Henry Spencer]

In article >,
Derek Lyons > wrote:
>Your memory fails. Gemini briefly was intended to come down on land
>(under a parawing), but Apollo was targeted for a water landing from
>the start.

Nope. Not if you go back to the very start. The original Apollo specs
called for land touchdown in the continental US... not just for a nominal
flight, but for most abort cases as well (which was seriously hard).
Significant work was done on land touchdown before the requirement was
relaxed; you can find early Apollo papers on things like braking rockets
and landing-gear design.

(The *reason* for this requirement was the same as the reason why the
original specs called for totally autonomous navigation with no ground
assistance at all, not even a voice link: Cold War security jitters.)

>>Again, I ma working from memory, each Apollo capsule could have bee
>>flown up to five times...
>
>Your memory fails. There never was any such thing considered.

Re-use of Apollo capsules was definitely *considered*, although by the
time hardware was actually flying, the idea had gone very much to the back
burner. Even so, the flight program did include one or two small test
objectives related to re-use.

>>Strongly, being heated to several thousand degrees before taking a sal****er
>>dunk did nothing for the capsules reusability.
>
>Your knowledge fails. The interior of the capsule is exposed to
>neither great heat, nor sal****er. The heatshield, which is so
>exposed, would have to be replaced each time regardless of landing
>mode.

Correct. As witness the successful reflight of one unmanned Gemini
capsule.

>>One of the primary arguments against a capsule is the need to mount a full
>>scale search and rescue effort every time one lands.
>
>Your knowledge fails. With few exceptions the capsules came down in
>the intended area, and neither search nor rescue was required.

Indeed, the landing precision was good enough that an operational system
could have landed just offshore, or even in a major lake, which would have
needed much less nautical infrastructure.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

[Henry Spencer]

In article >,
Brian Thorn > wrote:
>>Or you could design the SM functions into the same capsule. I don't see
>>where wings would have anything to do with reusability.
>
>If you can figure out how to do it that way, I'd be all for it, but I
>think a CM/SM one-airframe design is going to be so complicated...

Why? There was nothing very complicated in the SM. Indeed, some later
capsule designs, like BAe's Multi-Role Capsule, did incorporate very
nearly all the orbital hardware into the capsule itself. It means a
somewhat bigger and heavier capsule, but by and large it doesn't add much
complexity.

It is a little tricky to find a capsule configuration which can
accommodate a full RCS/OMS system, but the MRC design managed, with minor
operational limitations.

The only thing which does add complexity is if you want major deployable
appendages, like antennas or solar arrays, on a capsule. That was the one
thing MRC did use an expendable service module for: the SM held the solar
array and possibly some of the antennas.

>From a practical point of view, I think an X-20/HL-20-type airframe lends
>itself much more to reusable service components than an Apollo or
>Soyuz-like capsule does.

There is no real reason why that would be so, given design for it from the
start. Once on the ground, one is much like the other... except that the
aerodynamic lander is typically bigger, heavier, and more complex.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

[Henry Spencer]

In article >,
Derek Lyons > wrote:
>Wings, or a lifting body, or Roton's blades, all allow for greater
>crossrange and more predictable and precise targeting of the landing point.
>
>This has a lot to do with reusability and routine operations.

Crossrange has nothing in particular to do with reusability, and makes
only the most minor contribution to routine operations unless flight rates
are very high.

Given the accurate descent navigation demonstrated by Apollo and ARD, a
gliding parachute is almost certainly sufficient to make pinpoint landings
with a capsule.

By the way, capsules can do powered landings. The early work on rotor
landings was for Apollo, and several other powered-landing approaches were
explored and seemed feasible. "Manned spacecraft: engineering design and
operation", Purser et al eds, 1964, has some interesting papers on this.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

[Henry Spencer]

In article >,
Brian Thorn > wrote:
>I wasn't talking about the payload, I'm talking about the orbital
>maneuvering system, power, long-duration life support, and fuel that
>the Service Module carries. They're heavy and expensive, and they're
>thrown away with all of the capsule concepts...

No, wrong. See the BAe Multi-Role Capsule papers in the Feb 1989 issue of
JBIS, for example.

The obsession with adding expendable service modules to reusable capsules
is the result of trying to make the capsule itself as small as possible.
But making the capsule bigger really costs very little, given adequate
launcher diameter, and it can ease many design problems.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

[Henry Spencer]

In article >,
Derek Lyons > wrote:
>Handwaving away the shock problems inherent in a land touch down, no
>they are not a particular challenge. Modifying the Apollo capsule so
>that it can tolerate the shock is a very different matter.

This is actually quite straightforward to solve, if you are willing to
postulate a new design which exploits the greater capsule size possible.
On close examination, the hard part of a touchdown without some sort of
terminal velocity reduction (braking rockets, parafoil flare maneuver,
whatever) is trying to reduce the velocity to zero with a very short
shock-absorber stroke.

But there is *no reason* why the stroke has to be so short! Make the
outer (aerodynamic) hull substantially larger than the inner (pressure)
hull, so there is room for a long-stroke shock-absorber system in between.
If you have the extra size -- quite feasible, for an EELV launch -- then
you just need a chief designer who is willing to dig in his heels and
insist that the empty space within the outer hull will *remain* empty, and
will *not* fill up with equipment/cargo/etc. just because it's there.

And that's assuming you're still using Apollo-style parachute descent,
rather than interesting alternatives like rotor landing, jet lift,
deploying a hot-air balloon rather than a parachute, etc.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

[Henry Spencer]

In article >,
Brian Thorn > wrote:
>>And keep in mind... a capsule is going to be lighter for the same
>>capabilities, as it doesn't have all those dead weight wings etc.
>
>Instead, it will have to have a honkin' big parachute/airfoil which
>had better deploy just right.

Capsule designs routinely provide redundancy in parachutes. (Try doing
that with wings. :-))

>Even then, you might still need a retro
>rocket to make landing bearable for the crew.

Not if you use a gliding parachute with a flare maneuver, or simply make
the capsule big enough for a decent shock-absorber stroke.

>And how big a capsule can they fit on top of a Delta or Atlas before
>they start getting into aerodynamic problems that make wings look
>easy?

Rather bigger than the winged vehicle which can go up on the same launcher
without incurring much worse aerodynamic problems.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

[Paul F. Dietz]

Henry Spencer wrote:

> By the way, capsules can do powered landings. The early work on rotor
> landings was for Apollo, and several other powered-landing approaches were
> explored and seemed feasible.

How hard would it be to make the 'capsule' be a low-performance
upper stage, and use its engine to do a powered landing as in
the various SSTO concepts?

Paul

[OM]

On Sat, 23 Aug 2003 18:44:35 GMT, (Henry Spencer)
wrote:

>Flight vehicles should not be thought of as permanent assets to be
>passed on to your grandchildren.

....On the other hand, if my granddad had left me a couple of F-14s, or
even an F-111, I wouldn't have bitched too loudly :-)


OM

--

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- General George S. Patton, Jr

[Henry Spencer]

In article >,
Paul F. Dietz > wrote:
>> By the way, capsules can do powered landings...
>
>How hard would it be to make the 'capsule' be a low-performance
>upper stage, and use its engine to do a powered landing as in
>the various SSTO concepts?

The configuration is a little awkward, because both the heatshield and the
engine(s) want to point down. And the optimal acceleration for a liquid-
fuel upper stage tends to be fairly low. The idea is not ridiculous, but
I suspect it's not the best way of doing things. It looks better for an
SSTO, which has to solve the configuration problem anyway and has lots of
engine power available.

Turbojet lift engines were investigated in the 1960s, and they looked to
be mass-competitive with lifting bodies, if both were required to handle
reasonable contingencies (e.g., go-around capability for the lifting
body). However, either had about half the payload of a vehicle with a
gliding parachute (plus backup chute).

One very interesting idea, which looked like it might be mass-competitive
with parachutes and could deliver a very low touchdown velocity, was to
deploy a drogue chute and have it pull out, instead of a main parachute, a
hot-air balloon. Initially it functions as a reefed parachute, and then
you light a burner. The downside is that control is in the vertical
dimension only.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

[Hallerb]

>And that's assuming you're still using Apollo-style parachute descent,
>rather than interesting alternatives like rotor landing, jet lift,
>deploying a hot-air balloon rather than a parachute, etc.
>--

How about a mars like air bag?

[Tim Shoppa]

(Henry Spencer) wrote in message >...
> Flight vehicles should not be thought of as permanent assets to be
> passed on to your grandchildren.

The B-52 scampers around this proclomation by being passed down
to great-grandchildren and great-great-grandchildren instead :-).

Tim.

[Derek Lyons]

(Henry Spencer) wrote:

>In article >,
>Derek Lyons > wrote:
>>Wings, or a lifting body, or Roton's blades, all allow for greater
>>crossrange and more predictable and precise targeting of the landing point.
>>
>>This has a lot to do with reusability and routine operations.
>
>Crossrange has nothing in particular to do with reusability, and makes
>only the most minor contribution to routine operations unless flight rates
>are very high.

I shouldn't call relaxing of flight constraints a minor contribution,
nor an increase in abort options.

>Given the accurate descent navigation demonstrated by Apollo and ARD, a
>gliding parachute is almost certainly sufficient to make pinpoint landings
>with a capsule.

"Pinpoint" may be a bit of a stretch. I've never seen a diagram of
the landing eclipse vs landing location for the Apollo missions. It
was also helpful that the landing target could be moved, both in
mission planning and in realtime, as desired. A lake, land, or
coastal target does not offer that freedom.

D.
--
The STS-107 Columbia Loss FAQ can be found
at the following URLs:

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[Henry Spencer]

In article >,
Derek Lyons > wrote:
>>Crossrange has nothing in particular to do with reusability, and makes
>>only the most minor contribution to routine operations unless flight rates
>>are very high.
>
>I shouldn't call relaxing of flight constraints a minor contribution,
>nor an increase in abort options.

An increase in abort options, while useful, doesn't impinge on routine
operations very much: by and large, it doesn't enable flights that used
to be ruled out.

And unless I've missed something, I don't believe you get a lot in the way
of relaxed flight constraints out of higher crossrange -- you're going to
have to explain that one in more detail before I'll buy it.

>>Given the accurate descent navigation demonstrated by Apollo and ARD, a
>>gliding parachute is almost certainly sufficient to make pinpoint landings
>>with a capsule.
>
>"Pinpoint" may be a bit of a stretch. I've never seen a diagram of
>the landing eclipse vs landing location for the Apollo missions.

Numbers for Apollo landing errors are not hard to find (see, e.g., "Apollo
By The Numbers") and they're not large, typically a kilometer or three.
In itself that is not pinpoint, but note that I was talking about adding a
gliding parachute to that -- those errors are small enough that a bit of
late aerodynamic maneuverability ought to suffice to take them out and
permit landing exactly at a chosen point.

>It was also helpful that the landing target could be moved, both in
>mission planning and in realtime, as desired.

Helpful, yes, but that's different from "essential". The one real issue
is weather, and that you handle the same way aviation does, by having
backup sites.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

[Andrew Gray]

In article >, Henry Spencer wrote:
>>
>>"Pinpoint" may be a bit of a stretch. I've never seen a diagram of
>>the landing eclipse vs landing location for the Apollo missions.
>
> Numbers for Apollo landing errors are not hard to find (see, e.g., "Apollo
> By The Numbers") and they're not large, typically a kilometer or three.
> In itself that is not pinpoint, but note that I was talking about adding a
> gliding parachute to that -- those errors are small enough that a bit of
> late aerodynamic maneuverability ought to suffice to take them out and
> permit landing exactly at a chosen point.

Okay, here's a question. If you had a gliding parachute, how pinpoint
would pinpoint be? With late-descent manouevering, I assume Apollo could
never land in a duckpond, but could you reasonably expect to hit, say, a
small lake? An Olympic-sized swimming pool? A pre-selected coastal bay?

Just an intriguing sidenote...

--
-Andrew Gray

[Richard Schumacher]

Henry Spencer wrote:

> In article >,
> Derek Lyons > wrote:
> >Handwaving away the shock problems inherent in a land touch down, no
> >they are not a particular challenge. Modifying the Apollo capsule so
> >that it can tolerate the shock is a very different matter.
>
> This is actually quite straightforward to solve, if you are willing to
> postulate a new design which exploits the greater capsule size possible.
> On close examination, the hard part of a touchdown without some sort of
> terminal velocity reduction (braking rockets, parafoil flare maneuver,
> whatever) is trying to reduce the velocity to zero with a very short
> shock-absorber stroke.
>
> But there is *no reason* why the stroke has to be so short! Make the
> outer (aerodynamic) hull substantially larger than the inner (pressure)
> hull, so there is room for a long-stroke shock-absorber system in between.
> If you have the extra size -- quite feasible, for an EELV launch -- then
> you just need a chief designer who is willing to dig in his heels and
> insist that the empty space within the outer hull will *remain* empty, and
> will *not* fill up with equipment/cargo/etc. just because it's there.

And split the problem into two: stroke in landing legs, followed by stroke in the
couches. A combined three or four meters will make landings feel almost cushy
:_>

[Henry Spencer]

In article >,
Andrew Gray > wrote:
>> In itself that is not pinpoint, but note that I was talking about adding a
>> gliding parachute to that -- those errors are small enough that a bit of
>> late aerodynamic maneuverability ought to suffice to take them out and
>> permit landing exactly at a chosen point.
>
>Okay, here's a question. If you had a gliding parachute, how pinpoint
>would pinpoint be?

Depends on the piloting, more than anything else. My understanding is
that given good visibility and reasonable flying conditions, sport
parachutists consider a couple of meters to be a sizable error. But a
capsule is going to have more limited maneuverability, and the pilot's
view of the ground isn't going to be very good, although GPS guidance
might well help.

My first guess (with a caution that it's not an area where I'm very well
calibrated) would be a 95% chance of landing within 50m of the target.

That may be too pessimistic; X-38, which landed under a parafoil rather
than as a lifting body, was supposed to be able to do a fully automatic
runway landing, which implies a crossrange error of at most a few meters.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

[Marshall Perrin]

Henry Spencer > wrote:
> That may be too pessimistic; X-38, which landed under a parafoil rather
> than as a lifting body, was supposed to be able to do a fully automatic
> runway landing, which implies a crossrange error of at most a few meters.

This suggests an entirely different way of dealing with the landing
stroke requirement. The only problem I see is convincing a bunch of
hot-shot test pilots that they have to land on a giant feather mattress...

- Marshall

[LooseChanj]

On or about Wed, 27 Aug 2003 03:12:52 GMT, Greg D. Moore (Strider)
> made the sensational claim that:
> Umm, I'm not sure, but I think putting the bathroom outside the pressure
> hull might not go over well. :-)

Bah. I've had to go worse places.
--
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[Mary Shafer]

On Sat, 23 Aug 2003 18:08:43 GMT, (Henry Spencer)
wrote:

> In article >,
> Derek Lyons > wrote:
> >Wings, or a lifting body, or Roton's blades, all allow for greater
> >crossrange and more predictable and precise targeting of the landing point.
> >
> >This has a lot to do with reusability and routine operations.
>
> Crossrange has nothing in particular to do with reusability, and makes
> only the most minor contribution to routine operations unless flight rates
> are very high.

It's true that crossrange (and downrange) and reusability aren't
related for the hardware, but crossrange is very important in the
reusability of the wetware. Being able to land at a predicted
location makes crew recovery effective.

> Given the accurate descent navigation demonstrated by Apollo and ARD, a
> gliding parachute is almost certainly sufficient to make pinpoint landings
> with a capsule.

Er, Apollo, like Gemini, had enough L/D for some crossrange and
downrange control. I think Apollo had about 0.5 and Gemini about 0.3.
There was more to the reentry trajectory than just ballistics and
parachutes. Actual aerodynamics played a part, too.

Mary

--
Mary Shafer Retired aerospace research engineer

[Henry Spencer]

In article >,
Mary Shafer > wrote:
>> >This has a lot to do with reusability and routine operations.
>> Crossrange has nothing in particular to do with reusability, and makes
>> only the most minor contribution to routine operations unless flight rates
>> are very high.
>
>It's true that crossrange (and downrange) and reusability aren't
>related for the hardware, but crossrange is very important in the
>reusability of the wetware. Being able to land at a predicted
>location makes crew recovery effective.

Some degree of crossrange *control* is important to make semi-precision
landings. But the *amount* of crossrange available determines nothing
except the orbital waiting time and/or maneuvering needed to bring the
orbit track over the desired landing point. This becomes really important
only when the flight rate is so high that a twelve-hour wait puts a real
crimp in the scheduling.

>> Given the accurate descent navigation demonstrated by Apollo and ARD, a
>> gliding parachute is almost certainly sufficient to make pinpoint landings
>> with a capsule.
>
>Er, Apollo, like Gemini, had enough L/D for some crossrange and
>downrange control.

But *not* enough for pinpoint landings. (Defined as: anyone who stands
on the exact aim point had better be prepared to move aside fast.) Even
with some modern improvements like GPS (as tested on ARD), the error due
to remaining navigation uncertainties, high-altitude winds, etc. is still
measured in kilometers.

The problem is that most of the aerodynamic maneuvering capability occurs
very early in reentry, while a lot of the error creeps in later, when the
ability to correct for it is very limited. Pinpoint landing requires, or
at least is greatly aided by, some degree of low-speed aerodynamic
maneuverability -- a gliding parachute, a rotor, jet lift, whatever.

>I think Apollo had about 0.5 and Gemini about 0.3.

Apollo was about 0.35, Gemini 0.19. Apollo was *meant* to get about 0.5,
flying at an angle of attack of 33deg, with the windward side of the cone
essentially parallel to the airflow... but the crowded interior made it
impossible to offset the center of mass enough to trim it for 33deg.

(Ironically, in the end it would have cost almost nothing in mass to make
the CM a bit bigger, giving a roomier interior and more trim flexibility.
Its diameter was dictated by early ideas about the diameter of Saturn
upper stages, but the rockets kept getting bigger, and in the end there
was no compelling reason why the CM had to be that small. Losses like the
growth in heatshield area would have been largely canceled out by gains
like the lower ballistic coefficient and hence less severe reentry.)
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

[jeff findley]

Mary Shafer > writes:
>
> Er, Apollo, like Gemini, had enough L/D for some crossrange and
> downrange control. I think Apollo had about 0.5 and Gemini about 0.3.
> There was more to the reentry trajectory than just ballistics and
> parachutes. Actual aerodynamics played a part, too.

This worked out well for Apollo, allowing it to generate enough lift
to markedly change the reentry profile on lunar missions. A quick
search turns up a reference at my favorite space reference site:

Skip lunar reentry trajectories studied for Apollo
http://www.astronautix.com/details/ski16333.htm

I just found out the JSC Digital Image Collection's text search is
case sensitive! Searching for "apollo reentry" or even "apollo"
results in zero pictures found. However, "Apollo reentry" finds lots
of pics. Go figure. I don't see the picture I remember which shows
what the skip trajectory looked like on a 2D plot. Any good book on
Apollo would have this picture.

Jeff
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