Genesis Auger - End of Manned Capsule Worship?

"Edward Wright" wrote in message
m...
Richard Schumacher wrote in message
...

A ram-air parachute is about 9% of landed weight. If you're not the
trusting sort and want a backup, you're now up to 18%. Wings
typically
account for about 20%, so the difference is not very great.

There are costs besides the mass of the components themselves. For
example during ascent wings induce aerodynamic bending loads on the
structure and increased drag.

Not necessarily. Bending loads depend on the location of the wing
relative to the center of gravity. Drag does increase, but so does
lift. With proper design, it can be a net win.

Would it be fair to say that a capsule is roughly 15% more mass efficient
than a winged design for a given down mass? That is that aero surfaces,
structural mass increase due to variable stresses, and horizontal type
landing gear will result in a vehicle with only 15% more landing mass than
a symetrical VL capsule.

I was under the impression that the difference is much greater than that,
in the 50-100%+ range including the structural mods. If it is that or less,
then the argument for HL is strengthened. I would like to see a curve that
somewhat specifies the mass requirements for an HL vehicle to match mass
performance with the 'simple' capsule. Even a numerical comparison as
flawed as my thing on minimum airbreather requirements would be a start.

I believe there may be a structural configuration for HL vehicles that
matches
that of VL vehicles. I consider HL desirable if affordable. Trying to figure
a
better layout is a waste of time if the sum differences are already within
15%
of so. A slightly bigger launcher would gain the HL advantages at minimal
cost if the low percentage is true.

A quick technical question, has anyone ever considered quickly winching
the parachute in to reduce vertical landing velocity? It requires a bit
of power but might be lighter and safer than landing rockets.

There are a number of possible ways of doing it. One method,
(basically a large gas ram), would be to make a flexible tube from a
series of spheres, on pressurization the spheres inflate and length
reduces, (by pi/2). This could form part of the main parachute line.
Pressurization could be provide by a high pressure cylinder, small
explosive charge, energy of descent, etc.

Another trick might be a small explosion, (fuel/air?), beneath the
parachute, (like the Medusa), this should be quite light weight and
simple, and the failure mode is just a hard landing.

Pete.

On 15 Sep 2004 21:33:35 GMT, (George William
Herbert) wrote:

X-38 flared at 8 fps; that's nowhere near what carriers land at.

It's half the limit of 16 fps.

Mary

--
Mary Shafer Retired aerospace research engineer

(George William Herbert) wrote in message ...

A circular parachute
will give you less control, so your choice of landing site will be
constrained by a possible off-filed landing in a backup situation.
Thus, you lose some of the advantages of having a ram-air chute in
the
first place.

One of my design assumptions for capsules is that the landing point
will eventually be on the worst possible spot (sharp heavy rock,
solid thick cement, whatever). If your design assumption is that
you have to avoid injury WHEN that happens, then landing on the nice
prepared raked sand at Dugway or wherever is just gravy.

I was thinking of the true worst case -- coming down in the middle of
I-80 at rush hour or in a schoolyard at recess. That's not something
you can design for, it's something you have to factor into selection
of your drop zone. If your backup system is significantly less
accurate than your main system, the backup becomes the limiting
factor.

Vertical touch-down velocities for X-38 were about twice those of
carrier landings. That may not approch physiological limits, but I
wouldn't call it comfortable, either.

X-38 flared at 8 fps; that's nowhere near what carriers land at.

I think you may have mistaken feet and meters. Marti Sarigul-Klijn
reported the average vertical landing velocity as 20 fps (6 m/s) and
the maximum as 27 fps (8.2 m/s). From the videos I've seen of X-38
landings, I can easily believe that. A carrier landing is about 10 fps
(3 m/s), so it's quite a bit harder.

Either one might be a hard sell for certain missions, though. The
ISS
ambulance mission, for example.

If the flight controls lock up on a winged ISS ambulance CEV,
the vehicle is a writeoff,

Perhaps you've forgotten that on the last flight of SpaceShip One, a
flight control did lock up. Mike Melvill simply went to a backup
system. You're assuming a winged vehicle with no more rendundancy than
a model airplane, which isn't likely to be the case.

and the crew either all die or
the evacuee can't survive a parachute hop and dies or the
evacuee gets an unpleasant personal parachute ride but survives.

Or they have an escape capsule. I find rather strange that people who
advocate using capsules as routine transportation always seem to
overlook the possibility of using them as emergency systems.

"redneckj" wrote in message m...

Would it be fair to say that a capsule is roughly 15% more mass efficient
than a winged design for a given down mass? That is that aero surfaces,
structural mass increase due to variable stresses, and horizontal type
landing gear will result in a vehicle with only 15% more landing mass than
a symetrical VL capsule.

That sounds a bit low. As a starting point, though, you might look at
SpaceShip One. If you were to remove the wings, SpaceShip One would
look very much like a symmetric capsule, so if you estimate the weight
of the wings vs. parachutes, etc., it should give you a starting
point.

I was under the impression that the difference is much greater than that,
in the 50-100%+ range including the structural mods. If it is that or less,
then the argument for HL is strengthened. I would like to see a curve that
somewhat specifies the mass requirements for an HL vehicle to match mass
performance with the 'simple' capsule. Even a numerical comparison as
flawed as my thing on minimum airbreather requirements would be a start.

Here are the masses of crewed reentry vehicles from the 60's.

Gemini (2 crew) - 1,983 kg.
Soyuz TM (3 crew) - 2,802 kg
Apollo CM (5 crew) - 5,806 kg.
Big Gemini (9 crew) - 5,227 kg
X-20X Dyna-Soar (5 crew) - 5,165 kg.

In each case, I've shown the weight for the reentry section only and
for Apollo, I've shown the maximum crew in the rescue configuration,
rather than the crew actually carried. For the X-20X, I used the
weight for the basic X-20 configuration, since that's all I have. X-20
and X-20X were to have the same form factor, so it's probably not too
far off.

On a mass basis, the Big G capsule appears to be much more efficient
than Dyna-Soar. To be fair, however, Dyna-Soar was a reusable vehicle,
so it would probably reenter with some equipment that a capsule would
simply discard in orbit. So, the difference might not be quite as
large as it appears.

The Gemini, Soyuz, and Apollo capsules, however, don't seem to be much
more efficient than Dyna-Soar. All of them are in the range of
900-1200 kg per person. Apollo, not Dyna-Soar, is the heavy-weight of
the group.

So it appears that capsules can, in theory, be more efficient, but in
practice, other design choices can outweigh that difference.

Edward Wright wrote:

In each case, I've shown the weight for the reentry section only and
for Apollo, I've shown the maximum crew in the rescue configuration,
rather than the crew actually carried.

Somewhere around here I have Rockwell document showing how to pack six in an Apollo. A dedicated "taxi" Apollo
could dispense with a lot of the instrumentation Apollo usually had, clearing up space.

For the X-20X, I used the
weight for the basic X-20 configuration, since that's all I have. X-20
and X-20X were to have the same form factor, so it's probably not too
far off.

It's about right.



On a mass basis, the Big G capsule appears to be much more efficient
than Dyna-Soar. To be fair, however, Dyna-Soar was a reusable vehicle,
so it would probably reenter with some equipment that a capsule would
simply discard in orbit. So, the difference might not be quite as
large as it appears.

Plus Dyna Soar had better cross-range, for what that's worth.

The Gemini, Soyuz, and Apollo capsules, however, don't seem to be much
more efficient than Dyna-Soar. All of them are in the range of
900-1200 kg per person. Apollo, not Dyna-Soar, is the heavy-weight of
the group.

So it appears that capsules can, in theory, be more efficient, but in
practice, other design choices can outweigh that difference.

If you want the maximum in capsule efficiency... look at something like MOOSE. Well under 500 lbs/person, not
counting the rather important space suits.

"Scott Lowther" wrote in message
...


Edward Wright wrote:

In each case, I've shown the weight for the reentry section only and
for Apollo, I've shown the maximum crew in the rescue configuration,
rather than the crew actually carried.

Somewhere around here I have Rockwell document showing how to pack six in
an Apollo. A dedicated "taxi" Apollo
could dispense with a lot of the instrumentation Apollo usually had,
clearing up space.

Well for one thing, forgo the "stroke" of the center couch. This was left
in in the rescue version because they assumed they might have an injured
patient who could not survive a hard landing.

There's a 12 person version I think Henry Spencer has mentioned. But I
think that's pushing it.

And a modern version could probably free up even more room.

Plus Dyna Soar had better cross-range, for what that's worth.

For an operational system, it definitely helps.

Pete Lynn wrote:
A quick technical question, has anyone ever considered quickly winching
the parachute in to reduce vertical landing velocity? It requires a bit
of power but might be lighter and safer than landing rockets.

This has been proposed, mechanically winching the chute in
just prior to touchdown.

I am not personally terribly in favor of the method, but it
is certainly on the table of decellerator methods...

There are a number of possible ways of doing it. One method,
(basically a large gas ram), would be to make a flexible tube from a
series of spheres, on pressurization the spheres inflate and length
reduces, (by pi/2). This could form part of the main parachute line.
Pressurization could be provide by a high pressure cylinder, small
explosive charge, energy of descent, etc.

I hadn't seen that idea specifically proposed.
It seems workable... but feels, without having
run any numbers... like it will be too heavy.

Another trick might be a small explosion, (fuel/air?), beneath the
parachute, (like the Medusa), this should be quite light weight and
simple, and the failure mode is just a hard landing.

I don't recall seeing that idea suggested before.

It sounds slightly insane... but I can't think of why it wouldn't
work ok. The overpressure is going to be unfriendly to the
capsule and landing region, but the length of the parachute
tether can be increased to attenuate it.

Easily testable, too.

Nice idea. Have to see how far it flies when numbers are
applied...


-george william herbert

Edward Wright wrote:
(George William Herbert) wrote:
A circular parachute
will give you less control, so your choice of landing site will be
constrained by a possible off-filed landing in a backup situation.
Thus, you lose some of the advantages of having a ram-air chute in
the
first place.

One of my design assumptions for capsules is that the landing point
will eventually be on the worst possible spot (sharp heavy rock,
solid thick cement, whatever). If your design assumption is that
you have to avoid injury WHEN that happens, then landing on the nice
prepared raked sand at Dugway or wherever is just gravy.

I was thinking of the true worst case -- coming down in the middle of
I-80 at rush hour or in a schoolyard at recess. That's not something
you can design for, it's something you have to factor into selection
of your drop zone.

Right. The system should be designed so that worst case credible
winds and worst case credible landing ellipse error can't add up
to the capsule landing in densely populated areas, unless there
is a truly catastrophic out of control re-entry or something
(in which case all bets are off no matter what design approach
you have chosen... ).

If your backup system is significantly less
accurate than your main system, the backup becomes the limiting
factor.

True. But with appropriate drop zones, that parameter works
out to "how hard is the landing on the passengers" because
you land outside the nicely pre-prepared sand bunker area,
not "how many kindergartners does it squash".

For a water touchdown, there is a technical argument to
be made that a company doing capsules based in the
San Francisco Bay area would want to land them in
San Pablo Bay (northern arm of "San Francisco Bay"
comples). However, it fails the ellipse safety test.
Which is a pity, because using a small motor boat for
recovery and retrieval instead of an aircraft carrier
is really attractive.

Vertical touch-down velocities for X-38 were about twice those of
carrier landings. That may not approch physiological limits, but I
wouldn't call it comfortable, either.

X-38 flared at 8 fps; that's nowhere near what carriers land at.

I think you may have mistaken feet and meters. Marti Sarigul-Klijn
reported the average vertical landing velocity as 20 fps (6 m/s) and
the maximum as 27 fps (8.2 m/s). From the videos I've seen of X-38
landings, I can easily believe that. A carrier landing is about 10 fps
(3 m/s), so it's quite a bit harder.

www.parachutehistory.com/space/iss.html says it's 8 ft/sec

The Astronautix entry shows 3.7 m/s sink rate during landing,
which is 12.2 ft/sec.

As Mary indicated, carrier planes land at 16 ft/sec sink rate.

As with any parachute, once you know the actual flight
performance of a chute or parafoil concept, you can adjust
the sink rate by adjusting the chute area, or limiting the
payload weight. Designing with capacity (weight/volume)
margins in the chute and parafoil systems is easy.

Also, really... the velocity is secondary. What hurts is the
decelleration, which is the velocity and the shock absorber
or crush structure stroke distance and energy absorbtion.
So as long as the structure can take 20 fps, if the people
inside have space and shock absorbers to take that over
some reasonable time and shock absorber stroke, it's not
a problem in any way. Or the whole vehicle can have
shock absorbers or airbags or something.

Either one might be a hard sell for certain missions, though. The
ISS
ambulance mission, for example.

If the flight controls lock up on a winged ISS ambulance CEV,
the vehicle is a writeoff,

Perhaps you've forgotten that on the last flight of SpaceShip One, a
flight control did lock up. Mike Melvill simply went to a backup
system. You're assuming a winged vehicle with no more rendundancy than
a model airplane, which isn't likely to be the case.

No, I'm thinking of catastrophic flight control failures in
a number of aircraft over the last few decades. Complete power
(electrical or hydraulic) failures happen, and will kill FBW
vehicles like returning winged spacecraft. The odds can be
made very low, but they will remain nonzero.

and the crew either all die or
the evacuee can't survive a parachute hop and dies or the
evacuee gets an unpleasant personal parachute ride but survives.

Or they have an escape capsule. I find rather strange that people who
advocate using capsules as routine transportation always seem to
overlook the possibility of using them as emergency systems.

I'm not sure why you'd have an escape capsule.

You have a capsule to protect people from the space
environment. You don't need to be protected from
the air on landing. You want to be protected from
a hard landing, but plenty of parachutists do that
just fine without anything but their legs (and arms).

By the time you want or need to bail out of a crashing
space capsule, you're at low enough altitude to do fine
with a personal chute.

Besides, the weight penalties will be pretty bad...

What do you see that they would add that's significantly
useful, as opposed to just having individual parachutes
possibly with a good assured crew bailout extraction
system of some sort, like ejection seats or tractor
rockets or a pole or the like?


-george william herbert

Scott Lowther scottlowtherAT, ix, DOT, netcom, DOT, com wrote:
Edward Wright wrote:
In each case, I've shown the weight for the reentry section only and
for Apollo, I've shown the maximum crew in the rescue configuration,
rather than the crew actually carried.

Somewhere around here I have Rockwell document showing how to pack six
in an Apollo. A dedicated "taxi" Apollo
could dispense with a lot of the instrumentation Apollo usually had,
clearing up space.

The Apollo CM had 1,500 kg of electrical and electronic systems.
Just using modern systems there will save the vast bulk of that
mass and volume... there's enough volume in there to put two
more people, so that gets you to eight (6 for rescue max combo,
no seat landing stroke, plus two more).

More significant redesigns, and perhaps another foot of diameter
or so, get you a lot more people in sardine can mode...


-george william herbert