Abandoning Orion for a Next Generation Shuttle?

David Spain wrote:
In that way, the effort of lifting them is never wasted.

Excellent point. Do we know how effective solids are at high altitudes?

Like all rocket engines they should be more effective at high altitude
than at sea level, due to decreased external air pressure generating
increased thrust due to the pressure differential inside and outside of
the engine being greater.


I am under the impression that they effectively supply their own
oxidation once combustion temperatures are reached, is that correct?
Assuming air resistance is reduced they could be very effective.

Yes, they contain their own oxidizer in their fuel, but specific impulse
tends to be lower than liquid-fueled engines for the same weight of
propellants.


Bring the casings back down and they could be refueled as well.
Might not be the prettiest looking spacecraft but very serviceable.

Another approach would be to use the equivalent of a PAM module or
a final stage to provide orbital insertion as well as an escape
system.


That would work, although trying to make a solid stage recoverable after
it reenters is probably more trouble than it's worth from a monetary
sense. If you design the motor to be single-use, you not only save the
weight of the TPS and parachutes, but can make the casing out of wound
fiber composites rather than steel (like on the Shuttle SRBs) and save
yet more weight that way.

The key is to keep pushing, it doesn't really matter who does
the pushing. The nice thing about a liquid fueled escape system based
on a top stage is that you could cut it off at various points in the
flight profile. Allow escape with return or escape with sub-orbital
return to remote landing sites. But of course, it does need to be
reliable. Hypergolic?


For simplicity's sake as well as reliability that would be the obvious
alternative to solid fuel. You would also almost certainly make it
pressure fed rather than using turbopumps for the same reasons if you
went the liquid-fueled route.
But that would cut back its performance to the point where it would be
around the same as the solid-fueled type, and the solid one would be a
lot simpler to make, and probably cheaper as well.

Pat

Pat Flannery writes:
For simplicity's sake as well as reliability that would be the obvious
alternative to solid fuel. You would also almost certainly make it pressure
fed rather than using turbopumps for the same reasons if you went the
liquid-fueled route.
But that would cut back its performance to the point where it would be around
the same as the solid-fueled type, and the solid one would be a lot simpler to
make, and probably cheaper as well.

One could also take the Scaled Composites approach and use a hybrid upper
stage, with a combo of liquid oxidizer feeding a solid fuel.

That would give you a cutoff ability during the flight profile, while
maintaining the advantage of the simpler solid fueled engine.

Dave

Greg D. Moore (Strider) wrote:
In that way, the effort of lifting them is never wasted.

This has been proposed before and has some merit. In fact I'd say the OMS
burns during launch (as opposed to the OMS-1/2 burns) are similar to this.

It's a pity that the OMS engines don't have enough thrust to peel the
Shuttle off of the stack while the SRBs are burning, as that would make
a good LES.
Gemini would have salvo-fired its four retrorockets to separate itself
from the Titan II in a emergency once it had climbed beyond the
effective altitude limit of its ejection seats.

Pat

David Spain wrote:

One could also take the Scaled Composites approach and use a hybrid upper
stage, with a combo of liquid oxidizer feeding a solid fuel.

That would give you a cutoff ability during the flight profile, while
maintaining the advantage of the simpler solid fueled engine.

That's certainly another way, but the nitrous oxide they used as a
oxidizer has to be kept from overheating, or it will go into a vapor
state...as they found out the hard way during the fatal accident with
the SpaceShipTwo engine.
KSC gets pretty hot in summer, and that could pose a safety problem in
regards to using that type of motor, at least with N2O as the oxidizer.

Pat

Pat Flannery writes:
The Shuttle was already over-budget and was
generating nowhere near the savings in launch cost over the use of expendable
boosters that had been promised when the program began. NASA probably figured
that a few more problems and delays for redesigns could end the program, and
wanted to keep flying even if safety concerns were evident (the multiple
launch scrubs on Challenger were making it look like a lemon to the news media
also) Combined with the very high launch rate that NASA wanted to do in 1986,
and you had all the things in place for a disaster.

Another way to think about it, delays and cost overruns are par for the
course for most government undertakings. They usually are swept under the
rug, there are execeptions, such as the M247 Sgt. York DIVAD. But a Crit-1,
well, that's a tough one to sweep.

I won't dispute the issue that "launch fever" was certainly an issue with
the Challenger accident and that the previous scrubs were putting pressure on
to get it launched. But the problem had evidenced itself more than a year
before the Challenger incident. The management thinking you mention was truly
flawed if it really thought that delays and redesigns are more likely to kill
a program than a Crit-1.

However...

Experience now tells us that a single Crit-1 will get you 50% of the way
to program termination. Two Crit-1's places the program on a path to
'retirement'. Three Crit-1's and you're done I suspect.

I can guarantee you that if NASA had it all to do over again it would have had
some sort of escape system on board, even if it were just souped-up ejection
seats for the crew; more likely it would have ended up being something like
this system that was proposed after Challenger:
http://www.spaceref.com/news/viewnews.html?id=780

I can't speak for the B-52 escape capsules, but when it comes to escape pods,
if our experience with the B-1 Lancer program is at all relevant, it isn't
a very good record. It would be a very novel system indeed to have ejection
seats in the mid-deck. But not unheard of. There was the F-104A jet fighter
that offered a downward firing ejection seat. There's the horrible video
I've seen of Iven Kincheloe's take-off abort, where he is desperately trying
to intentionally roll the aircraft at about 100ft off the deck to get it
into an attitude so that he could eject into something other than tarmac.
Alas, to no effect, it crashed and killed him before he could complete the
maneuver. That was the end of downward firing ejection seats on all future
jet fighters.

http://www.vectorsite.net/avf104_1.html
http://www.ejectionsite.com/f104seat.htm

Whether something like that could have saved Columbia's crew is a open
question, as the orbiter broke up while experiencing high aerodynamic and
thermal loads that might well destroy the escape pod and capsules as well.


Agreed. And of course that's exactly the nub. It's only in these types of
situations that they're likely to be needed anyway.

My take on all this: prevention is usually better than a cure.

Dave

Pat Flannery writes:

Pat Flannery wrote:
http://www.spaceref.com/news/viewnews.html?id=780

Whether something like that could have saved Columbia's crew is a open
question, as the orbiter broke up while experiencing high aerodynamic and
thermal loads that might well destroy the escape pod and capsules as well.

As a follow-up on that, if you were going to design some sort of aerodynamic
reusable launch vehicle like Shuttle or VentureStar again, then the Soviet
Spiral spaceplane might show a really good way of designing a escape capsule
if you were to scale the size of it up to include the whole crew:

Making the escape 'capsule' a part of the shuttle is an interesting idea.

But if we're making the shuttle smaller anyway, why not put the emphasis on
making the TPS as robust as possible. And here's an added idea. If the thing
is going to use a drag parachute to slow it down on a runway, why not make it
a drogue chute as well? Then if you get into control surface problems, trip
the drogue until you've slowed down enough to trip the emergency parachute
trio? Come down to a hard bump landing, but it's still a landing.

Dave

David Spain writes:

I can't speak for the B-52 escape capsules, but when it comes to escape pods,
if our experience with the B-1 Lancer program is at all relevant, it isn't
a very good record.

Pat,

Speaking of B-1s, don't know if they're still flying out of Ellsworth AFB,
but if they are, and you're traveling to your neighbor to the south and in
the vicinity of Rapid City, it's worth it to stop by the McDonalds off exit
67 on I-90. Grab a Mac-meal to go and hang out in their parking lot.

The great big "hill" behind the MacDonalds, if you look carefully has some
interesting lighting arrangments along its flat top. And just about the
time you notice that, you'll notice something else quietly zipping by
directly overhead at about 200ft!

:-)

Dave

David Spain wrote:

Pat said we should start a thread about what we learned from the Space Shuttle
Program that could be applied to a next generation shuttle project. So I'm
doing so, under a deliberately provocative 'Subject' heading just to grab
attention. But seriously, there's no doubt that there is likely not enough
room in NASA's budget to do both Orion and a next gen Space Shuttle.

So to kick things off, here's a few gleanings I've read here and elsewhere
that'd be good starting points.

0) Do we have numerous and sustainable flight rates?

First, drop the buzzword 'sustainable' and define the question in
useful terms.

Then we can talk.

D.
--
Touch-twice life. Eat. Drink. Laugh.

http://derekl1963.livejournal.com/

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

David Spain wrote:

Whether something like that could have saved Columbia's crew is a open
question, as the orbiter broke up while experiencing high aerodynamic and
thermal loads that might well destroy the escape pod and capsules as well.


Agreed. And of course that's exactly the nub. It's only in these types of
situations that they're likely to be needed anyway.

My take on all this: prevention is usually better than a cure.

My take: greatly increasing weight and complexity in order to obtain
a marginal increase in 'safety' is a fool's errand. Find some other
way, or man up and accept reality.

D.
--
Touch-twice life. Eat. Drink. Laugh.

http://derekl1963.livejournal.com/

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

(Derek Lyons) writes:

First, drop the buzzword 'sustainable' and define the question in
useful terms.

Then we can talk.

D.
--

OK sure.

I don't *know* the planned flight rate for Constellation/Orion
assuming it doesn't get canned post Augustine commission.

I would *assume* it depends on the mission. If the return-to
the-moon objective is abandoned that leaves only flights to
the ISS. So how many of those are needed per year after the
shuttle is retired? The ground infrastructure for shuttle
limits us to single digits per year. I guess I don't see that
changing with Orion flights to the ISS only missions, since
the ground infrastructure remains nearly the same. Do you?

How many flights are needed if the return-to-the-moon 'vision'
proceeds? I have seen no proposed numbers.

The Orion capsule I gather is supposed to be reusable,
so we're only discarding LVs on every launch, correct?

Do we know the turnaround time and cost to refurbish an
Orion capsule for each flight? I hope it's less than the
shuttle. It is *supposed* to be, correct?

In a reduced size shuttle, we're still discarding the LVs
so no net win there. For ISS orbital missions it
will be Aries-I's. Is there a plan to recover the solid
booster section on Aries-I like there are for shuttle SRBs?
So it's only the upper stage and CEV's SM that is tossed
each time? That would seem to be likely to be less expensive
on paper than would be tossing out something like a Delta
heavy each time.

So if you venture that the capsule Aries I system is highly
'reusable' then what we're really discussing is vehicle
flexibility on return. A flyable shuttle design gives cross
range and multiple abort options while a capsule requires
multiple abort sites that have to staffed. If the capsule
is only water landing that adds a good deal of cost to
the landing and retrieval infrastructure. Costs that I don't
have a good handle on.

Dave