The other space shuttles???

[9GClub]

What is our space program accomplishing?

http://www.thespaceplace.com/nasa/spinoffs.html

We also fly in space 'cause it's there.



In related news, this insulation-shedding propensity is freaking me out, guys. NASA brass is now saying that the largest piece that fell off this time "could have been bad"...... by which of course they mean a repeat of three years ago. As much as I love to see them fly, blowing chunks so consistently is unacceptable.

I'm sure they've looked into alternative fuel sources.... wasn't Spaceship One a few months ago powered by solid rubber and alcohol? Don't quote me on that, but something like that might eliminate the need for thermal insulation. Somebody who knows what they're talking about please chime in.

 

[Fly_Chick]

atlantis is in the vehicle assembly building having been or about to be mounted to the stack of the external tank and solid rocket boosters for the sept. launch but that is now in jeapordy after a large piece of foam still came off the tank during the discovery launch.

How many orbiters fit in the VAB at one time?

 

[Bluto]

What is our space program accomplishing?

If we had something more efficent, maybe we could do something more with it than re-arrange satellites and stick pieces on the ISS. I think space exploration is important to our future, but if NASA can't handle it maybe privately owned and financed operations are the way of the future. I just have to wonder, considering the cost, if the shuttle is the best tool for the job.

 

[canyonblue737]

How many orbiters fit in the VAB at one time?

certainly only one in the stacked configuration, but perhaps you could fit another waiting to go since the building was made to house the saturn V. i have never seen more than 1 in there at a time.

 

[EagleRJ]

-Challenger was originally intended to be the test vehicle, while Enterprise was going to be a flight vehicle. They were switched due to the fact that Enterprise was going to be finished far earlier.

-SpaceShipOne was powered by a cast solid fuel consisting mostly of tire rubber, with nitrous oxide as an oxidizer. That choice of fuel had the advantage of being benign and non-explosive, but it lacks the Specific Impulse (basically gas mileage) of hypergolics. The liquid hydrogen/oxygen powered engines on the Orbiter develop far more thrust per pound of propellant.
The SS1 doesn't require the same thermal insulation as the Shuttle because it isn't exposed to the same heat. SS1 essentially freefalls from 360,000', and the only heating is due to the speed built up from falling in a vacuum. It has a lot of drag in the "feathered" position, and doesn't weigh a lot, so Mach number- and heating- is kept to a minimum. The Shuttle is orbital, and must aerobrake from around 18,000 MPH in order to re-enter the Earth's atmosphere. It obviously weighs a lot for its frontal area, so heating is much higher.

-There have been several attempts to develop a replacement for the Shuttle. The most mature was the X-33, a single stage to orbit lifting body with a more efficient "aerospike" engine that would serve as a technology demonstrator for a much larger version, called the VentureStar. The program was making good progress, but was killed due to funding issues.
Sounds like this flight may be the last for a while. NASA has grounded the Shuttle fleet pending resolution of the debris issue.

 

[bocefus]

"How many orbiters fit in the VAB at one time?"

3 stacked and one horizontal, if you had 4 total.

 

[SuperFLUF]

Can't we do better than 30 year old technology? Why are we still relying on these dinosaurs for our space program?

Money, money, money, monaaaay............

We could do better, and have had plans to do better, but nobody wants to pay for it.

The X-30 would have been a step in the right direction:

http://www.fas.org/irp/mystery/nasp.htm

 

[mzaharis]

http://www.thespaceplace.com/nasa/spinoffs.html

We also fly in space 'cause it's there.



In related news, this insulation-shedding propensity is freaking me out, guys. NASA brass is now saying that the largest piece that fell off this time "could have been bad"...... by which of course they mean a repeat of three years ago. As much as I love to see them fly, blowing chunks so consistently is unacceptable.

I'm sure they've looked into alternative fuel sources.... wasn't Spaceship One a few months ago powered by solid rubber and alcohol? Don't quote me on that, but something like that might eliminate the need for thermal insulation. Somebody who knows what they're talking about please chime in.

I find that justifying NASA as industrial policy due to spinoffs is suspect. Certainly, we have gotten certain technological spinoffs from NASA. The question is, however, what economic benefit would you have gotten from either leaving that money in the public's pocket, or investing in any other arbitrary technical goal (say, the Superconducting SuperCollider, or Sematech, or some other technological investment). Dual-use technologies, as much as NASA tries to draw attention to them, are few and far between. Economists generally find a poor return on investment for money invested this way. Don't get me wrong, I'm a strong supporter of human spaceflight, I'm just not going to pretend that Mylar, Formulaid, and improved golfballs is the reason why it is a valuable investment, or that these or similar technologies wouldn't come around if the money were left in the public sector. The program needs to be justified first and foremost on what it gives us in terms of exploration and expanding the human vista.

Space exploration and high energy physics always use the "Spinoffs" argument, because many people are unable or unwilling to accept that the primary benefit of these fields (expansion of human knowledge) is an end that justifies public investment, even of the relatively small amounts involved by NASA (<1% of US Gov't budget, part of which is industrial research for the aerospace industry, making that next Boeing airplane that much better - OK, maybe Boeing should pay for that itself).

SpaceShip One uses the fuel system due to simplicity of engine design and manufacture for a throttleable engine. It doesn't make any difference on the thermal protection system, which comes into play on reentry, when the engines are off. SpaceShip One had a much more benign thermal entry regime due to its relative low speed (<M4, vs. M25 on Space Shuttle entry interface).

BTW, the shuttle solid rocket engines use a combination of aluminum powder, a rubber binder/fuel, and ammonium perchlorate as the fuel and oxidizer.

EDIT - Sorry Eagle RJ, read your response - you had already addressed some of this.

 

[mzaharis]

-There have been several attempts to develop a replacement for the Shuttle. The most mature was the X-33, a single stage to orbit lifting body with a more efficient "aerospike" engine that would serve as a technology demonstrator for a much larger version, called the VentureStar. The program was making good progress, but was killed due to funding issues.

I remember it having some terrible technology issues, such as the inability to build appropriate fuel and oxidizer tanks out of Carbon Fiber (carbon and resins tend to react badly with liquid oxygen). I was getting rather skeptical that they could have gotten the appropriate propellant mass fractions that would have been necessary to make VentureStar a viable project. They had to back off of their performance claims a number of times, and that went a long way to killing off the project.

 

[NuGuy]

Heyas all,

Anyone wonder why the external tank of the shuttle has all these problems lately?

Didn't they launch 50-60 flights with minimum problems with the tank?

The answer is actually in how the foam insulation is produced for the exterior of the external tank. Some flights back the chemical makeup for the foam was changed to a more "enviromentally friendly" formula, and it just can't stand up to the rigors of the job. They got lucky with a few flights before the Columbia disaster.

NASA knows that this is the problem, but for PR and other reasons, will not go back to the old method of manufacture.

Nu

 

[EagleRJ]

The answer is actually in how the foam insulation is produced for the exterior of the external tank.

I think most of the problems that have arisen from the new foam are related to application, not the properties of the foam itself. The new CFC-free foam is applied in a different way, and NASA has had trouble getting it applied without creating internal voids.

The problem with the foam, and the cause of most foam debris events, is a phenomenon called "cryopumping". That's when a void in the foam is refrigerated by the liquid fuel in the tank, which causes the air in the void to contract, drawing in additional air from the atmosphere. When the Shuttle is launched and aerodynamic heating heats up the void, the gas expands so much that it pops a chunk of foam off the tank. Spraying foam on the tank and getting it absolutely free of voids is tough, but the porosity of the foam also plays a part. I think the new environmentally-friendly foam is more porous and more prone to cryopumping.

The basic problem with debris is the general design of the Shuttle stack. Previous multi-stage rockets lost plenty of foam and other debris, but it wasn't in danger of damaging the vehicle. With the Shuttle, we've got fragile, mission-critical componants (the RCC on the leading edge) behind and below material that is prone to fall off. In retrospect, that's a bad idea! Any future winged-recovery vehicles will need to be smaller designs that are mounted at the very top of the launch vehicle to avoid damage from falling debris.

 

[mzaharis]

Some of these problems have been occurring all along, but weren't thought to be "safety of flight" issues. They've beeng getting dings in tiles for a long time. Just that, after a certain chunk (the bipod covering, which isn't a spray-on, but a glue-on) fell off and shattered a leading edge RCC panel, leading to a loss of spacecraft, people have been noticing what has been happening much more closely. I also believe that EagleRJ is correct that new foam mandated by environmental considerations has led to greater problems with foam adhesion.

If you're at the library and don't mind poring through back issues of Aviation Week, they had some great articles on the subject - you'll just have to go through the last year's issues.

 

[9GClub]

SpaceShip One uses the fuel system due to simplicity of engine design and manufacture for a throttleable engine. It doesn't make any difference on the thermal protection system, which comes into play on reentry, when the engines are off. SpaceShip One had a much more benign thermal entry regime due to its relative low speed (<M4, vs. M25 on Space Shuttle entry interface).

Eagle and MZ,

Thanks for the info, that helped.

The thermal insulation I was referring to is the foam on the external tank, not the tile matrix on the orbiter. A SS1-esque fuel configuration (or something besides LOX/hydrogen) would make a difference because you wouldn't need to insulate the fuel tank(s).

Alternatively, fly with the current fuel setup and just bolt the landing craft to the top of the rocket. That wouldn't solve NASA's apparent birdstrike problems (I'd love to see a video clip from the camera that caught that incident), but it would be a step in the right direction in terms of foam impacts.

 

[mzaharis]

Eagle and MZ,

Thanks for the info, that helped.

The thermal insulation I was referring to is the foam on the external tank, not the tile matrix on the orbiter. A SS1-esque fuel configuration (or something besides LOX/hydrogen) would make a difference because you wouldn't need to insulate the fuel tank(s).

Alternatively, fly with the current fuel setup and just bolt the landing craft to the top of the rocket. That wouldn't solve NASA's apparent birdstrike problems (I'd love to see a video clip from the camera that caught that incident), but it would be a step in the right direction in terms of foam impacts.

Yeah, NASA may use a solid fuel rocket (the existing Shuttle SRB) for the CEV, and the spacecraft would be mounted on top, out of the way. There are some good histories about why the Shuttle ended up with its current configuration, and it was all due to seemingly sound engineering decisions, but they all led to a very problematic vehicle configuration (solid rocket booster joints next to a liquid hydrogen tank, delicate thermal protection systems downstream from fragile foam insulation and ice accumulations, wacky load paths in an asymmetrical vehicle, etc.). Many of these requirements were due to the fact that the DOD kicked in money for it to be used for Defense missions (largely dropped after Challenger), particularly the large crossrange requirement for "abort-once-around" launches from Vandenburg (which never took place - read about the "Curse of Slick 6")

http://www.dailynexus.com/science/2001/1875.html

 

[TurboS7]

To be auctioned off at a TBA date, keep a watch out in your local USA Today.


ie: they would make a great restraunt