Genesis Auger - End of Manned Capsule Worship?

It is not hard to imagine a similar result with a manned
capsule. Perhaps Constellation will have wings after all.

- Ed Kyle

On Wed, 08 Sep 2004 11:13:16 -0700, edkyle99 wrote:

It is not hard to imagine a similar result with a manned capsule.
Perhaps Constellation will have wings after all.

Manned capsules have (almost) always had reliable results with
parachutes--partly because they've had multiple chances to work
out the bugs in the design, redundancy, etc.

Wings fail, too.

For earth to low orbit shuttles, I prefer wings and runway
landings. For high energy reentry, a capsule is probably more
practical.

--Damon

wrote in message
...
It is not hard to imagine a similar result with a manned
capsule. Perhaps Constellation will have wings after all.

Doesn't help you if your APU's die and you have no control of your
aerodynamic surfaces.

We'll have to wait to see what happened to Genesis to cause it to not deploy
its parachutes. It's entirely possible that the failure has absolutely
nothing to do with the capsule versus wings debate.

Jeff
--
Remove icky phrase from email address to get a valid address.

"Jeff Findley" wrote in message
...

wrote in message
...
It is not hard to imagine a similar result with a manned
capsule. Perhaps Constellation will have wings after all.

Doesn't help you if your APU's die and you have no control of your
aerodynamic surfaces.

Right. The point being that no method is inherently "best".



We'll have to wait to see what happened to Genesis to cause it to not
deploy
its parachutes. It's entirely possible that the failure has absolutely
nothing to do with the capsule versus wings debate.

Jeff
--
Remove icky phrase from email address to get a valid address.

wrote:

It is not hard to imagine a similar result with a manned
capsule. Perhaps Constellation will have wings after all.

Only if it's designers are idiots. Any crewed craft will be extensively
tested before it carries a crew. And of course a crew can always fire
chute mortars manually if needs be.

"Richard Schumacher" wrote in message
...
wrote:

It is not hard to imagine a similar result with a manned
capsule. Perhaps Constellation will have wings after all.

Only if it's designers are idiots. Any crewed craft will be extensively
tested before it carries a crew. And of course a crew can always fire
chute mortars manually if needs be.

Always?

Even if say the mortar's damaged? The firing circuits are corroded, etc?

Remember, it was a passive item on Columbia that doomed it and an
essentially passive item on Challenger that failed.

If passive items can fail, I can think of even more failure modes for active
items.

Nothing is perfect.

And of course a crew can always fire
chute mortars manually if needs be.

Always?

Even if say the mortar's damaged? The firing circuits are corroded, etc?

Backup chutes/mortars; backup circuits and batteries.

While this *is* rocket science, it is also generations old.

Greg D. Moore (Strider) wrote:


It is not hard to imagine a similar result with a manned
capsule. Perhaps Constellation will have wings after all.

Only if it's designers are idiots. Any crewed craft will be extensively
tested before it carries a crew. And of course a crew can always fire
chute mortars manually if needs be.


Always?

Even if say the mortar's damaged? The firing circuits are corroded, etc?

Remember, it was a passive item on Columbia that doomed it and an
essentially passive item on Challenger that failed.

If passive items can fail, I can think of even more failure modes for active
items.

So can we all. Now, can you assess the probabilities of these modes,
and the costs of mitigating them? Fixed wings on non-military
orbiting/landing spacecraft add costs which outweigh their benefits.



Nothing is perfect.

And some things are less perfect than others: components and systems
which cannot be tested are always less perfect than those which are
tested.

Richard Schumacher wrote in message ...

So can we all. Now, can you assess the probabilities of these modes,
and the costs of mitigating them? Fixed wings on non-military
orbiting/landing spacecraft add costs which outweigh their benefits.

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.

And some things are less perfect than others: components and systems
which cannot be tested are always less perfect than those which are
tested.

What makes you think parachutes are easier to test?

Edward Wright wrote:
Richard Schumacher wrote:
So can we all. Now, can you assess the probabilities of these modes,
and the costs of mitigating them? Fixed wings on non-military
orbiting/landing spacecraft add costs which outweigh their benefits.

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.

Ram-air parachutes are heavier than normal circular ones for the
same landed weight. Look at, oh... BRS (www.brsparachutes.com),
the BRS-182 model (Cessna 182, max suspended weight 3040 lbs,
parachute system weight 85 lbs, less than 3% of the landed weight).

If you want or need a ram-air chute, you can back it up with
an equivalent circular chute. Or two, each of which is about
half the size, and a sixth the weight. If both backups work
then the landing velocity is the same, if one fails then the
landing velocity is sqrt(2) higher and the G-loads 2x as large,
but that's probably not a problem. The landing loads will
have to be "human comfortable" anyways, not approaching the
maximum physiological limits for routine service. 2x comfortable
loads is still 'safe' in the 'injures very few people' sense.
The statistics for chute failures, multiple chute failures,
and impact surface conditions can be worked out to arrive
at acceptable injury risk. A hard landing 1% of the time,
with expected injuries of 0.1 or lower in the hard landing,
is less than 1E4 risk per passenger. Which people will
almost certainly go for, including insurance companies.
And the real numbers are better than that.

If the main fails and both of the backup circular chutes fail,
see my post from yesterday about personal chutes. The added
vehicle system mass for those (even if you include a rocket
tractor extraction system to pull the crew out of the capsule)
is going to be trivial. The risk seems to be detailed tradeoff
of added risk of having large solid rockets inside the cabin
for the extraction system, and all the possible failure and
undesired actuation issues with that, versus people climbing
out on their own. At some point someone will have to figure
out how hard it is to climb out of a worst case falling
spinning capsule, a task I do not envy but have on roadmaps.


-george william herbert