Re: Returning an ET: was Re: NASA Targets June Launch for Space Shuttle Atlantis

lol, looks like he got it right to me. Restaurant, Swimming pool, 3-D
Basketball court, Garden module, LEO Commodities Futures Market ...

Why turn a 500 Million dollar tank in LEO back into a 4 Million dollar tank
on the ground? Add a parachute, and the tank is negative sitting back on
the ground, real quick.

My library at work has it in PDF! I wouldn't hang my hat on this
paper. A few highlights (pardon the poor OCR spacing):

Under "Assumptions and Their Consequences"

The model used i n t h i s analysis was assumed to be a perfectly
smooth cylinder. The SSET is far from smooth; numerous
pipes and s t r u t s form protrubances likely
to experience heating far in excess o f t h e
s t a g n a t i o n region heating. It is possible
t h a t f a i l u r e o f t h e tank could r e s u l t from
s t r u c t u r a l weakening caused by the d i s i n t e -
g r a t i o n of an appendage experiencing highly
l o c a l i z e d heating. Only f u r t h e r study
w i l l r e v e a l t h e f u l l extent o f the problem,
i f indeed there is a problem. Even i f the
assumption of a smooth surface for the
SSET is i n e r r o r , and it looks unlikely
t h a t an i r r e g u l a r external tank could survive
re-entry, a l l is not l o s t . I n situat
i o n s such as these, it is well advised engineering
p r a c t i s e to make r e a l i t y conform
to the analysis model and make t h e s u r f a c e
o f t h e SSET smooth. This could be e a s i l y
accomplished during t h e i n - o r b i t r e t r o f i t
o f t h e tank. A spray-on foam i n s u l a t i o n
could be applied by a t e l e o p e r a t o r device
while payload is being loaded i n t o t h e t a n k.

Under "Towards the Future"
A s is t h e conclusion of most f e a s i -
b i l i t y s t u d i e s , f u r t h e r study is recommended.
It may be economically i n f e a s i b l e t o
r e - e n t e r payload i n the otherwise u s e l e s s
e x t e r n a l tank because of the high i n d i r e c t
c o s t s of recovery. If t h i s is t h e case,
t h e r e is one f i n a l j u s t i f i c a t i o n f o r ree
n t e r i n g t h e e x t e r n a l tank; consider t h e
money to be made from t u r n i n g r e - e n t e r e d
SSET's i n t o r a t h e r unique r e s t a u r a n t s . If
people a r e w i l l i n g t o e a t i n o l d r a i l r o a d
c a r s , p o t e n t i a l space e n t r e p r e n e u r s could
make q u i t e a business o u t o f s e a t i n g hungry
d i n e r s i n t h e i n s i d e s of what was once
t r a v e l l i n g a t Mach t h i r t y !

Who, besides the people reading these groups, want to eat is a
resturant that has flown at Mach 30?

--Rolf

http://www.aiaa.org/content.cfm?pageid=406&gTable=mtgpaper&gID=66838

From the above page:

   The Space Shuttle external tank as a re-entry module

   KENT, S. (Aerojet Liquid Rocket Co., Sacramento, Calif.)
   AIAA-1979-888
   In: Conference on Advanced Technology for Future Space Systems,
   Hampton, Va., May 8-10, 1979, Technical Papers. (A79-34701 14-12)
   New York, American Institute of Aeronautics and Astronautics,
   Inc., 1979, p. 159-164.

If you click on the link to the "first page" of the PDF, you'll find that
stabilization of the orientation of the tank (so that it's got its "side"
facing the direction of flight) and rotation of the tank to reduce the
stagnation heating (by approximately a factor of two) are proposed as
methods of reducing entry heating.

This is only an AIAA paper, but it does show that someone was thinking about
this in the 70's.

Jeff

Good questions.  (Where's Mary or Henry when we need them? :-)

I suspect a stock tank wouldn't cut it.

But I wonder if you were willing to sacrifice a little payload, what changes
you could make to make it worthwhile?

I wonder if it was ever looked at.

"Greg D. Moore \(Strider\)" <mooregr_deleteth1s@greenms.com> wrote:

My gut feeling is no - not for a reentry from LEO.  

And even so - are the 'ridges' on the intertank structure 'tall
enough' to disrupt the boundary layer?  The extreme nose is less
insulated - what happens to it?

D.

I've always wondered what it would take to make an ET survive re-entry.

Put some sort of stabilization on it, chute for landing?

Would the existing SOFI work well enough as a ablative shield of some sort?

Even as a demo it could be interesting.  I mean the tank is sort of the
epitome of what people describe as ideal for re-entry, very light but
massive.

You mean the military requirements for a large payload bay and around 60k
lbs payload?  Or do you mean NASA's requiremnt to contain development costs
and (somewhat needlessly) constrain the overall vehicle size?  At one point,
NASA wanted a fully reusable launch vehicle with liquid fueled engines.
They certainly didn't move away from that desire because they thought it
would make the reoccurring costs lower.

True, it's not been done yet.  But the physics involved does seem to favor
keeping your empty tanks with your reentry vehicle if one of your design
goals is lower TPS requirements than the shuttle.

The reason the shuttle ET was designed with a propulsive tumble vent valve
is because the designers did not want the ET to remain intact when it
reentered.

Jeff

Certainly in _developing_ a 'sensible' reusable launch vehicle, you'd
keep the tanks.  But when you got around to actually _designing_ the
beast - you'd run into the same problems that caused NASA to back off
from that scheme, and which remain unsolved.

It's an open question whether they can be solved economically.

D.

The reasons you state have little to do with whether a spacecraft is winged
or not.  They have a lot more to do with other things, like how dense the
spacecraft is.  How dense it is impacts the TPS requirements.  The real
weakness is the fragile TPS.

By the way, the shuttle is very dense because it drops the lowest density
part of a launch vehicle, which is the empty propellant tanks.  It keeps the
heavy SSME's.  If you were designing a sensible reusable launch vehicle, you
wouldn't throw away the tanks, which makes the TPS requirements lower.

Jeff

I agree.  I think winged spacecraft are inherently bad for two reasons:

1.  The termal protection is fragile and complex.
2.  The weather requirements for ascent aborts and end of mission landing
are too high

I am a big fan of capsules for manned spacecraft.  Send the big payloads up
without people in a winged vehicle.  Wasn't Challanger carrying a TDRS?  Why
risk life to send up a payload such as this?

Danny Deger

Ironically, the very capabilities that made the STS so attractive to begin
with is leading to it's demise.  I think the Shuttle is a classic example
of how any system can become too complicated to manage effectively or
efficiently.

George

Op Thu, 12 Apr 2007 00:18:29 -0700, schreef Hyper:

Unless of course when a real rescue flight must be done.

Are you sure?

Unfortunately, the requirement for a rescue flight also means we'll
never see two shuttles in orbit at the same time.
THAT would be a publicity stunt I'd love to watch.

John Doe <jdoe@doe.org> wrote in news:89322$461d7eca$cef8887a$28578
@TEKSAVVY.COM:

LON rescue flight capability. The next orbiter won't be ready in time to
rescue 118 if Endeavour launches that early. That's the reality with a
three orbiter fleet as long as LON capability is a program requirement.

Unless the decision to extend the Shuttle's graveyard 2010 deadline has
already been taken (secretly) NASA cannot afford to postpone launches by
months.

Wasnt 118 supposed to go in late June ?

What would prevent NASA from launching Atlantis on june 8th and
Endeavour at end of June ?

April 10, 2007

Allard Beutel
Headquarters, Washington
202-358-4769

Kyle Herring
Johnson Space Center, Houston
281-483-5111

RELEASE: 07-83

NASA TARGETS JUNE LAUNCH FOR SPACE SHUTTLE ATLANTIS

WASHINGTON - NASA is targeting June 8 as the next possible launch
opportunity for space shuttle Atlantis' STS-117 mission to the
International Space Station.

Tuesday's decision by agency management followed a meeting that
reviewed the progress in repairing insulating foam on the shuttle's
external fuel tank, which was damaged during a sudden hail storm Feb.
26 at NASA's Kennedy Space Center, Fla. That damage required
engineers to repair approximately 2,660 sites on the tank.

The meeting also included an assessment of using the repaired
external
tank for the STS-117 mission versus swapping to one that arrived last
week from the manufacturing plant in New Orleans. Managers decided to
finish repairs to Atlantis' current tank and use it for STS-117. The
tank that arrived Friday will be prepared for space shuttle
Endeavour's STS-118 mission to the space station and now is targeted
for launch in August.

"The workforce has done an amazing job of assessing and repairing the
tank so far, but the sheer volume of repairs dictates moving the
launch target to June," said Space Shuttle Program Manager Wayne
Hale.

June 8 is the opening of the next available launch window for
Atlantis
to go to the station. STS-117 Commander Rick Sturckow, Pilot Lee
Archambault and mission specialists Jim Reilly, Patrick Forrester,
Steven Swanson and John "Danny" Olivas will continue training at
NASA's Johnson Space Center, Houston. During the 11-day mission, the
astronauts will work with the station crew and ground teams to
install a new, girder-like truss segment, unfold a new set of solar
arrays and retract one array on the starboard side of the station.

For more information about the STS-117 crew and mission, visit:

http://www.nasa.gov/shuttle

-end-