Author Topic: Shuttle as X-Vehicle  (Read 6944 times)

Offline Proponent

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Shuttle as X-Vehicle
« on: 07/04/2009 09:10 AM »
Jorge pointed out in a recent thread that one of the big mistakes of the Shuttle program was not building a research vehicle before attempting to build an operational one.

Well, if the Shuttle has never become truly operational, has it at least served as a de facto research vehicle?  Obviously it is larger and more expensive than a proper X-vehicle would have been, but has it taught us the same things?

If so, what are those lessons?

Offline Ben the Space Brit

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Re: Shuttle as X-Vehicle
« Reply #1 on: 07/04/2009 06:09 PM »
Well... for a start, putting a vehicle-survival critical system like TPS downstream of a known debris fall area is not smart.

That aside, NASA has probably learnt a lot about post-flight and reconditioning for reusable vehicles and engines.

[EDIT]
After my post, I realised that my first point would be a bit glib and that it should be further explained.

Unless I am very much mistaken, the problem of insulation foam coming loose from the ET and striking the orbiter's TPS was not known at the time STS was being designed.  Only later experience would show that this was a problem.

I would suggest that this is, first and foremost, an inherit fault with the concept of "all-up testing".  Whilst NASA got away with this when it rushed Saturn-V to IOC for Apollo 8, there were enough problems with the design that they dodged a bullet or two on that flight.  With STS they were not lucky (at least not in the long run).  Hopefully, in future, even though it will slow things down and might cost more, I hope that NASA would thoroughly test unknows such as a new type of vehicle arrangement or new form of tank insulation to ensure that there are no hidden problems before a crewed spacecraft is put in the way of any faults coming down the grade.
« Last Edit: 07/04/2009 06:24 PM by Ben the Space Brit »
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Offline whitewatcher

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Re: Shuttle as X-Vehicle
« Reply #2 on: 07/04/2009 06:19 PM »
I concur. It was sold to the public as the ultimate space-workhorse while at the same time incorporating many new elements: Reusability, large lifting body, ceramic TPS, 7 crew, on-board robotic arm, solid fuel rocket motors, ...

It's a pity that there will be no STS v2. I would have loved to see that. The wings would probably be much smaller (see CRV) and it would have no rudder.
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Offline lorahpj

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Re: Shuttle as X-Vehicle
« Reply #3 on: 07/04/2009 08:18 PM »
It's a pity that there will be no STS v2. I would have loved to see that. The wings would probably be much smaller (see CRV) and it would have no rudder.

Though it has been studied other times, an STS v2 study was done in the wake of the Challenger accident (see attached) and addressed the lessons learned at that point - namely the high costs and slow turnaround of the v1 system and safety issues known at the time (for example, Shuttle II eliminated the SRBs and created a crew escape system).

Foam damage would still have been an issue as would the increased risk of the orbiter striking orbital debris and damaging the TPS that way. 

It's an interesting "what if" to consider how the program might have been different if the Shuttle II replacement system had been given the green light.  Fielded in the late 90's to early 2000's, the Shuttle program might have had more frequent launches at greatly reduced costs.  A heavy lift vehicle was also part of the plan.  However, development of the replacement system might have meant that funding for the space station might have been redirected - ISS may not have become a reality and/or Mir might have been extended/become ISS.

Anyway, back on subject, Shuttle 1 delivered an amazing amount of technology, though, the design itself was incapable of meeting the original system goals (inexpensive, frequent launches).  Though it will be retired, I believe that it was ahead of its time and that eventually a successor system (if only in a spiritual sense) will developed.

Offline meiza

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Re: Shuttle as X-Vehicle
« Reply #4 on: 07/04/2009 08:40 PM »
If you have only one operational monolithic system providing a needed sustained capability, it's a bit hard to make changes to it.

STS, Manned spaceflight in this case.

The whole fundamental STS architecture choice allowed some nice incremental testing that probably improved safety greatly and reduced cost (orbiter glide flights for example) but it prevented some too (vertical takeoff horizontal landing with solids and expendable tank makes incremental flight testing, as well as aborts, very difficult).

It is very far from the X vehicle philosophy.

Offline NUAETIUS

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Re: Shuttle as X-Vehicle
« Reply #5 on: 07/04/2009 09:54 PM »
It is very far from the X vehicle philosophy.

You could almost say the the Shuttles reusability proves out the need, at least in the near term, for almost all space vehicles to be expendable, or at least designed with the assumption it will only be reused a few times.

If the Shuttle had been smaller and designed to be replaced every 4-5 launches (insert non replaceable main engines), it would have been upgraded over the years like the Soyuz and EELV fleets.  Also if each vehicle had a fixed life cycle, it would have allowed the external tanks to and solid rocket booster designs to be drastically altered as a new family of "Shuttles" came into use.

When the world goes back to the RLV, eventually, I hope we learn the lessons of the shuttle, and not lock ourselves in that generation of technology, and incorporate a more modular, expandable, and expendable approach.

Saturn rockets where bullets with no name, the Shuttle where Battleships with names to be remembered by history.  Shuttle proved that we need our space vehicles to be fighter aircraft, designed to be worn out and parked in a desert.
« Last Edit: 07/04/2009 09:58 PM by NUAETIUS »
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Offline vt_hokie

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Re: Shuttle as X-Vehicle
« Reply #6 on: 07/04/2009 11:00 PM »

It's an interesting "what if" to consider how the program might have been different if the Shuttle II replacement system had been given the green light. 

Perhaps it was given the green light...

http://www.aviationweek.com/aw/generic/story_generic.jsp?channel=awst&id=news/030606p1.xml

I'm not convinced, but still can't help but wonder!
« Last Edit: 07/04/2009 11:00 PM by vt_hokie »

Offline nooneofconsequence

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Offline khallow

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Re: Shuttle as X-Vehicle
« Reply #8 on: 07/05/2009 01:19 PM »

You could almost say the the Shuttles reusability proves out the need, at least in the near term, for almost all space vehicles to be expendable, or at least designed with the assumption it will only be reused a few times.

The economics of the Shuttle were known from the beginning. For some reason, they were expecting that the launch rate could be brought up to 40 or so launches a year and that there would be enough business to support that launch rate. Without that high launch rate, the overhead of a mostly reusable vehicle wasn't justified, just as we found out.

Quote
If the Shuttle had been smaller and designed to be replaced every 4-5 launches (insert non replaceable main engines), it would have been upgraded over the years like the Soyuz and EELV fleets.  Also if each vehicle had a fixed life cycle, it would have allowed the external tanks to and solid rocket booster designs to be drastically altered as a new family of "Shuttles" came into use.

Interesting idea, but I don't see the need to replace a vehicle every few launches. As I understand it, most of the vehicle isn't significantly stressed in each mission aside from the TPS and the engines.

Quote
When the world goes back to the RLV, eventually, I hope we learn the lessons of the shuttle, and not lock ourselves in that generation of technology, and incorporate a more modular, expandable, and expendable approach.

Saturn rockets where bullets with no name, the Shuttle where Battleships with names to be remembered by history.  Shuttle proved that we need our space vehicles to be fighter aircraft, designed to be worn out and parked in a desert.

I think we need to look at more mundane craft like cargo airplanes or small passenger jets. Fighter aircraft don't seem to me to be a good analogy. They need extremely high performance (for staying alive, for example) that isn't required by normal aircraft.
Karl Hallowell

Offline Jim

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Re: Shuttle as X-Vehicle
« Reply #9 on: 07/05/2009 02:01 PM »

It's an interesting "what if" to consider how the program might have been different if the Shuttle II replacement system had been given the green light. 

Perhaps it was given the green light...

http://www.aviationweek.com/aw/generic/story_generic.jsp?channel=awst&id=news/030606p1.xml

I'm not convinced, but still can't help but wonder!

http://www.thespacereview.com/article/576/1

Offline JohnFornaro

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Re: Shuttle as X-Vehicle
« Reply #10 on: 07/05/2009 04:11 PM »
That Aviation Week article was interesting:  "Two false claims don't make a postive".  Maybe the author was slyly suggesting that three claims would?  hardy har har.

Backing up to the foam problem.  Briefly what is the technical issue making it so heard to keep all the foam in place?
Sometimes I just flat out don't get it.

Offline Ben the Space Brit

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Re: Shuttle as X-Vehicle
« Reply #11 on: 07/05/2009 04:45 PM »
Briefly what is the technical issue making it so heard to keep all the foam in place?

IIRC, the geometry of the ET isn't smooth or regular around the forward orbiter attachment point, so air bubbles form underneath the foam when it is sprayed onto the tank.  Occasionally, the aerodynamic and harmonic forces during lift off knock chunks of it loose from that area as the air bubbles stop it adhering to the tank properly.  Unfortunately, the airflow from there heads right towards the leading edges of the orbiter's wings.
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DON'T PROPAGANDISE, FLY!!!

Offline meiza

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Re: Shuttle as X-Vehicle
« Reply #12 on: 07/05/2009 06:10 PM »

You could almost say the the Shuttles reusability proves out the need, at least in the near term, for almost all space vehicles to be expendable, or at least designed with the assumption it will only be reused a few times.

The economics of the Shuttle were known from the beginning. For some reason, they were expecting that the launch rate could be brought up to 40 or so launches a year and that there would be enough business to support that launch rate. Without that high launch rate, the overhead of a mostly reusable vehicle wasn't justified, just as we found out.

Shuttle couldn't launch every week anyway.

The lesson is NOT that reusables are bad. It's that STS doesn't work as an operational system.

Don't generalize too much.
« Last Edit: 07/05/2009 06:11 PM by meiza »

Online hop

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Re: Shuttle as X-Vehicle
« Reply #13 on: 07/06/2009 01:50 AM »
IIRC, the geometry of the ET isn't smooth or regular around the forward orbiter attachment point, so air bubbles form underneath the foam when it is sprayed onto the tank.
The CAIB report goes into detail, but it is greatly complicated by the extremes of the environment. The ET shrinks significantly as it cools down, air that gets close to the tank can liquefy and boil later, the outside gets hot enough to char noticeably...

It's amazing they've gotten it as good as they have really.

Offline Archibald

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Re: Shuttle as X-Vehicle
« Reply #14 on: 07/06/2009 05:45 PM »
Slightly "Off Topic" maybe, but of interest

OV-101 Enterprise ALT tests are well known.

There was a Langley proposal for a 1/4 subscale shuttle powered by a XLR-99.

Between the two was a third proposal

http://www.up-ship.com/drawndoc/drawndocspaceshuttle.htm

"A Shuttle Development Flight Test Vehicle"

Can't help thinking the three made a full, incremental test program.

1/4 subscale shuttle > Enterprise ALT > full-size hypersonic flights > STS-1

However budget decided otherwise...



... that ackward moment when you realize that Jeff Bezos personal fortune is far above NASA annual budget... 115 billion to 18 billion...

Offline Proponent

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Re: Shuttle as X-Vehicle
« Reply #15 on: 07/07/2009 02:21 AM »
Can't help thinking the three made a full, incremental test program.

1/4 subscale shuttle > Enterprise ALT > full-size hypersonic flights > STS-1

How much would this have helped, though?  It would have allowed the Shuttle's hypersonic aerodynamics to be pinned down accurately (Is it true that, because of mis-estimation of the center of pressure about a ton of dead weight had to be added to move the center of mass to compensate?). But otherwise, it seems as though the Shuttle's principal problems are operational, and I wonder whether this hypothetical test series would have been able to highlight those problems.

Offline Archibald

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Re: Shuttle as X-Vehicle
« Reply #16 on: 07/07/2009 05:57 AM »
Can't help thinking the three made a full, incremental test program.

1/4 subscale shuttle > Enterprise ALT > full-size hypersonic flights > STS-1

How much would this have helped, though?  It would have allowed the Shuttle's hypersonic aerodynamics to be pinned down accurately (Is it true that, because of mis-estimation of the center of pressure about a ton of dead weight had to be added to move the center of mass to compensate?).
But otherwise, it seems as though the Shuttle's principal problems are operational, and I wonder whether this hypothetical test series would have been able to highlight those problems.

Agree with the above. I wonder that, too, but this is not a board for alt-history!

IMHO it looks like the shuttle program could not really be stopped after Nixon  go-ahead in January 1972. Even Mondale/Carter preferred stopping the B-1A rather than the STS.

Didn't some Apollo astronaut (Stafford or Borman, can't remember) suggested stopping the shuttle program after STS-1, and turn it into some... X-vehicle ?

... that ackward moment when you realize that Jeff Bezos personal fortune is far above NASA annual budget... 115 billion to 18 billion...

Offline khallow

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Re: Shuttle as X-Vehicle
« Reply #17 on: 07/08/2009 01:42 PM »

You could almost say the the Shuttles reusability proves out the need, at least in the near term, for almost all space vehicles to be expendable, or at least designed with the assumption it will only be reused a few times.

The economics of the Shuttle were known from the beginning. For some reason, they were expecting that the launch rate could be brought up to 40 or so launches a year and that there would be enough business to support that launch rate. Without that high launch rate, the overhead of a mostly reusable vehicle wasn't justified, just as we found out.

Shuttle couldn't launch every week anyway.

The lesson is NOT that reusables are bad. It's that STS doesn't work as an operational system.

Don't generalize too much.

That's worth repeating. Sometimes we can learn the wrong lessons from these programs. As I see it, the Shuttle is a proof of concept for reusability technology that NASA made too big and used for too large a role.
Karl Hallowell

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