Why not external tank on X-33?

[carp]

The greatest problem with X-33 was the fuel internal tank too much heavy,right? Why not add an external tank (expendable or utilizable again)?

 

[gunsandrockets]

"The greatest problem with X-33 was the fuel internal tank too much heavy,right? Why not add an external tank (expendable or utilizable again)? "<br /><br />Then you are back to the old LockMart concept of the Starclipper shuttle, an option I raised in this other thread about how to redesign the Space Shuttle...<br /><br /><br /><br /><br />http://uplink.space.com/showthreaded.php?Cat=&Board=businesstech&Number=406131&page=0&view=collapsed&sb=5&o=0

 

[propforce]

Why would you think an external tank would be <i>lighter</i> than an internal tank? <div class="Discussion_UserSignature"> </div>

 

[carp]

Because the problem with X.33 was that the internal tank was too much eavy.

 

[carp]

"Then you are back to the old LockMart concept of the Starclipper shuttle"__________I think that Starclipper was a great design!

 

[carp]

The X-33 (and the follow up Venture Star) failed largely because it was technically unfeasible to build the vehicles with the kind of fuel fraction needed to be a single stage to orbit system. They tried to lighten the vehicle excessively and this led to cracking of the fuel tanks and a futile search for suitable heat shield material that is light enough. Even if funding was not pulled and they did fix the problems, it is doubtful that the X-33 would be able to reach orbital velocities -- even without a payload. Basically a 92% fuel fraction is simply unattainable in a vehicle that is to survive re-entry, and bring everything back. <br /><br />Nonetheless, the Linear Aerospike motor is largely a success. And if the vehicle is allowed to be heavier, it can be a lot more robust and feasible. I have always wondered if the system would work if they stop insisting that it be SSTO vehicle. What if they bolt a bundle of four 4 SRB cans side by side to the tail end of that thing? The SRBs will get it to 30km altitude and Mach 2.5. The vehicle then proceed with it's hydrogen aerospike engine. Would it have worked? <br /><br />

 

[spacefire]

<font color="yellow">The composite tankage that failed was forced on the designers by the size of the SCALE MODEL X-33. Had the vehicle been twice as large, scale factors would have allowed alloy metal tanks. So, in a roundabout way, you could say that tank weight was a problem.</font><br /><br />interesting insight...so you'resaying that the payload fraction of the VStar would have amde it a viable SSTO even with Aluminum tanks?<br />At the same time, the X33, which in actuality was not even supposed to reach orbital velocities, failed because it required ultralight tanks which could not be built with current technology?<br />If this indeed is true, it means the program's goals were viewed backwards which points to gross mismanagement of the program, ultimately leading to its cancellation while still technically viable. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[carp]

http://img383.imageshack.us/img383/8793/147xj.jpg http://img381.imageshack.us/img381/9420/x3317je.jpg http://img381.imageshack.us/img381/1060/017my.jpg

 

[gunsandrockets]

"I think that Starclipper was a great design!"<br /><br />I like the lighter 300 ton version of the Starclipper that used 3 x SSME. Of course it never had a chance since it's payload and crossrange weren't enough to meet USAF requirements. But for NASA's needs it would have been great, and maybe even lived up to the grandiose claims for a Space Shuttle system.

 

[gunsandrockets]

"... the follow up Venture Star) failed largely because it was technically unfeasible to build the vehicles with the kind of fuel fraction needed to be a single stage to orbit system."<br /><br />"I have always wondered if the system would work if they stop insisting that it be SSTO vehicle."<br /><br />Bingo.<br /><br />I think the effort to create viable SSTO RLV is a dead end. The best that might be hoped for is something less than that, such as a TSTO RLV or a Starclipper style 1-1/2 stage concept with an expendable drop tank. And critics of the RLV concept love to use the strawman of attacking the SSTO RLV concept as a way to claim that every RLV concept is impossible.<br /><br />

 

[vt_hokie]

<i>I like the lighter 300 ton version of the Starclipper that used 3 x SSME. Of course it never had a chance since it's payload and crossrange weren't enough to meet USAF requirements. But for NASA's needs it would have been great, and maybe even lived up to the grandiose claims for a Space Shuttle system.</i><br /><br />I would love to see them try it again and do it right this time! The CEV capsule proponents are always quick to point out that the capsule, despite its appearance, will have many advances over the Apollo command module. Well, the same holds true for a true space shuttle replacement. Imagine what we could do today with the available technology and without being hampered by the Air Force requirements that shaped STS.

 

[gunsandrockets]

"I would love to see them try it again and do it right this time!... Imagine what we could do today with the available technology and without being hampered by the Air Force requirements that shaped STS. "<br /><br />On the plus side of trying again, the SSME are going to be around for a long long time under current NASA plans. On the minus side it will be a titanic struggle to fund just the existing plan let alone find extra money for another go at a Shuttle. Ah, well...<br /><br />I think for RLV we will have to wait for some private effort to step into the breech. A t/Space capsule launched by Falcon V booster is my favorite candidate.

 

[scottb50]

That sounds pretty much like what I have been saying. A first stage X-33 type launch vehicle with a restartable second stage. Crew return vehicle, cargo container or other payload would attach to the upper stage.<br /><br />Once in orbit the second stage is used as a Tug or the Modules converted for other uses. Engines are used as spares, while failed engines are returned for repair or recycling. <div class="Discussion_UserSignature"> </div>

 

[gunsandrockets]

"Nonetheless, the Linear Aerospike motor is largely a success. And if the vehicle is allowed to be heavier, it can be a lot more robust and feasible. I have always wondered if the system would work if they stop insisting that it be SSTO vehicle. What if they bolt a bundle of four 4 SRB cans side by side to the tail end of that thing? The SRBs will get it to 30km altitude and Mach 2.5. The vehicle then proceed with it's hydrogen aerospike engine. Would it have worked?"<br /><br />Probably, but that choice combination isn't very efficient. The big advantage of aerospikes is altitude compensation. If the aerospike engine is only used as an upper stage engine then what's the point of using an aerospike instead of a conventional engine?<br /><br />How about this for a wacky way to launch Venturestar, a solid propellent booster assisted horizontal take off? Combine a solid rocket booster (maybe smaller than a shuttle SRB) with an external heavy landing gear structure that supports the loaded horizontal Venturestar at a nose raised attitude to the runway. At takeoff the booster ignites along with the aerospike engines. After liftoff the burnt out booster and landing gear structure is jettisoned (look out below!) and the Venturestar then climbs at an ever steeper angle until it is out of the atmosphere. I know this is a wacky idea, and I set it out more for amusement than anything else.<br />

 

[gunsandrockets]

"That sounds pretty much like what I have been saying. A first stage X-33 type launch vehicle with a restartable second stage. Crew return vehicle, cargo container or other payload would attach to the upper stage."<br /><br />Trying for a launch vehicle scheme similar to what you describe, it seems to me basing the LV design around using the 20 tonne Centaur LOX/LH2 stage as the upper stage would be a good starting point. I wouldn't even bother with trying to reuse the Centaur, just expend it, while trying to reuse everything else that goes into your launch vehicle system. This method resembles in many ways the t/Space launch architecture which uses a combination of reusable and expendable elements. <br /><br />

 

[spacester]

Interesting proposals. What if one was most interested in re-using the Centaur for orbital operations - could you do a first stage with multiple drop tanks and get enough advantage that way?<br /><br />What about a three stage system? Make the first stage totally reusable, flyback maybe but mostly make sure you keep its dV load low (~ 2 to 3 km/s) to keep its operational costs down. Make the second stage expendable and cost-efficient going to a bit higher and faster than normal Centaur separation. Put the Centaur on top of that and take it into orbit as a propulsion module, aka space tug. The launch payload would be the grapplers and other hardware needed to function as a tug or orbital fuel depot, integrated into the Centaur itself, no need for 'spacecraft deployment'.<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[dobbins]

"And critics of the RLV concept love to use the strawman of attacking the SSTO RLV concept as a way to claim that every RLV concept is impossible."<br /><br />The biggest problem with an RLV is the bloody thing has to be serviced. That means you have to have a service center.To make the service center economically viable you have to a high flight rate to spread the costs of running it over as many flights as possible. This is the bugbear that makes the Shuttle so darn expensive to operate.<br /><br />

 

[gunsandrockets]

"What about a three stage system?...Put the Centaur on top of that and take it into orbit as a propulsion module, aka space tug. The launch payload would be the grapplers and other hardware needed to function as a tug or orbital fuel depot, integrated into the Centaur itself, no need for 'spacecraft deployment'."<br /><br />I don't think you would want to use a Centaur stage as the basis of a reusable orbital tug. First off the Centaur has a balloon tank structure like the old Atlas booster, pretty fragile when empty. Secondly the cold LH2 that fuels the Centaur would be a bear storing and handling for orbital refuelling. <br /><br />Of course these very features make the Centaur an outstanding upper stage, lightweight and extremely efficient. This is why I recommended it as the core expendable element of a partially reusable launch vehicle system. Because the Centaur is so light, the reusable 1st stage can be smaller and lighter. <br /><br />

 

[mlorrey]

The bugbear is designing a TPS that needs tens of thousands of man-hours of maintenance every flight, and SRBs that are nearly as bad.<br /><br />As for RLV, the first law of RLV is this: you can have any two of the following features in an RLV, just pick any two and stick with the choice:<br /><br />a) hydrogen fuel<br />b) single stage<br />c) wings<br /><br />RLVs with all three features are most decidely impossible. RLVs with any two features are merely difficult.

 

[tomnackid]

We can give the x-33 a big external drop tank. That way we can enlarge the cargo bay. Make the tank big so we have enough fuel to add some actual wings to the orbiter so we can get some cross range and a bit slower landing speeds. With all this weight we might need some solid rockets to to get the whole thing off the pad. I'm thinking that with a litle work we could end up with something like this artists impression below <img src="/images/icons/wink.gif" /><br /><br />

 

[space_dreamer]

What! <br /><br />So you think it’s possible to have a SSTO RLV with wings and that uses a fuel other than Hydrogen.<br /><br />I would like to see that!!!!<br /><br />I was under the understanding the only reason to use hydrogen as a fuel was because you get more power for the weight (despite all the complications of having to have bigger tanks and keeping the fuel at such a low temp)<br /><br />If there a rocket fuel out there that could be handled like kerosene but is more powerful than Hydrogen.<br /><br />Firstly, what is it?<br /><br />Secondly, why aren’t we using it?<br />

 

[carp]

"We can give the x-33 a big external drop tank. That way we can enlarge the cargo bay".________________Yes,this is my idea.A modern starclipper design!

 

[tomnackid]

Actually, the Shuttle IS the modern Starclipper design--just stripped to the bare bones. A big cylindrical tank instead of the more complex wrap around tank. Solids to get it off the pad, Wings to keep the Air Force happy. <br /><br />The STS is what you get if you take the Starclipper concept and reduce development cost to the bare bones (the administration didn't give a hoot about OPERATING costs since they would be long one by the time the Shuttle was regularly flying!) while trying to cater to DOD needs at the same time. (That was the joke I was trying to make) <img src="/images/icons/wink.gif" />

 

[space_dreamer]

Yes, this is my idea. A modern starclipper design!<br /><br />- I would like to see that as well BUT NOT WITH NASA/US GOVERNMENT MONEY! <br /><br />Lockheed Martin could use the own money and years of experience to build a modern starclipper.<br />

 

[space_dreamer]

bump<br />