Space Shuttle 2.0

[BruceJohnJennerLawso]

So hello out there,

I was thinking a bit the other day about the whole topic of the Space Shuttle. From what I understand, the Space Shuttle program was just not competitive as a payload launch system, usually cited as being around 10000 dollars per kilogram to orbit, sometimes as high as 60000 per kilo when adjusted for full program costs, although I suspect that value must be slightly exaggerated. This contrasts with a price tag of about 5000 per kilo for the Soyuz, and around 3000-4000 per for the Proton (I think, dont quote me on that).

So obviously, the Shuttle would appear to have been more expensive than the competition, rather counter to the whole purpose of using space shuttles in the first place. The reasons for this are quite complex, but I thought Id post my ideas for how the design could be improved, if the idea were ever revisited again. (maybe not so likely)

Okay, so:

-Tear out those blasted SSMEs, and use disposable engines, particularly J-2s. Using the J-2 design would work nicely by allowing the design to be off the shelf, and having a restartable engine would also allow a shuttle launch to launch to orbit with no payload, then act as a kick stage for some payload waiting up there. That does imply the next point to the design, since the Shuttle itself cant be going with the space probe

-Once youve torn out those engines, dont put the J-2 on the Orbiter, put it on the External Tank. This is a bonus because it reduces the number of parts that need to be checked/repaired/replaced at the end of the mission, and it allows for a second use of the engine & external tank after the Shuttle Orbiter has detached. It also might make more sense to move the RCS systems to the body of the ET, so that the stack can maneuver easily once in Orbit (closer to the CG, which I would figure would be somewhere right below the orbiters wings while attached to the big orange tank) and it removes a really tricky ground maintenance operation with the Orbiter (defuelling the RCS).

-Of course you may be wondering how the hell the shuttle is supposed to deorbit. In the cavity left by the SSMEs, perhaps a solid fuel booster could be placed, also giving the shuttle a decent kick during an abort sequence too

So what do you think?

 

[sorindafabico]

-Tear out those blasted SSMEs, and use disposable engines, particularly J-2s.
(...)
Once youve torn out those engines, dont put the J-2 on the Orbiter, put it on the External Tank.

The idea remembers me the Buran design.

But I did not understand one thing: moving the RCS to the ET, you mean that the ET would be attached to the orbiter during the mission? This wouldn't limit orbital performance?

 

[Pipcard]

Solid boosters for deorbit (which requires precision) and abort sounds risky. I don't think there's any way you can safely separate a big spaceplane that is sitting right next to two giant solid boosters, while those giant boosters are burning (separating those burning solids first would result in the tank and orbiter being engulfed in SRB exhaust).

 

[Kyle]

Remove everything in relation to solids on the space shuttle, make it an entirely liquid fueled design.

 

[orbitingpluto]

If your not going to reuse engines(priced per part, the most expensive part of any rocket), why bother? Throw away tankage, throw away engines, and then your left with a hideously expensive payload shroud with the capability to carry people. Better in my opinion, to abandon the shuttle as it was completely, and instead embody it's ideals in a new machine that has a chance to make those ideas reality. A cheap reusable cargo truck to LEO could be possible, if the people going at it keep themselves trained to find the simplest, safest and cheapest way to go about it. If it's cheaper to toss away everything but a thermally protected reusable engine pod, they shouldn't be distracted by making the tankage reusable too. Feature creep is a large part of what went wrong with the shuttle, along with hubris(my opinion).

Solid boosters for deorbit (which requires precision) and abort sounds risky.

Solid rockets are extremely reliable, even more so than most liquid fueled rockets. The only match I know of is hypergolics, which are nasty toxic stuff. Plus, lack of precision isn't necessarily something that will always accompany solid rockets; a form of throttling could be only lighting off a few of of the multiple deorbit rockets, or sizing just one solid rocket based on the mission, which is compatible with the planning of a burn before the spacecraft leaves the ground that space agencies already deal with.

Remove everything in relation to solids on the space shuttle, make it an entirely liquid fueled design.

I think solids have a place in spacecraft and rockets, and I don't understand the bashing or need to toss them out of hand for liquids. While the Shuttle's SRBs did cause 7 people to die, other solid rockets have done their job without fault and done their jobs well, for example acting as part of ejection seats. A poorly designed or poorly cared for rocket can kill somebody, solid or liquid, and both types have. Well designed and well kept rockets can be safe even when exploding, even if that rocket has both solid and liquid propulsion on board, like Soyuz 18a. Solids can do things liquids can't do without having large drawbacks, like having a long storage time. Or safety, as solids are used in situations that demand them to work when asked and not go off at any other time; like ejection seats, or the Soyuz's landing rockets. There are real benefits that solid propellents have that liquids propellents don't, and a variety of situations where one works better than the other. I think rocket designers should be aware of the good and bad things of both types, and choose according to what is needed and what they have to work with, and not a no allowances rule.

 

[C3PO]

Solid rockets are extremely reliable, even more so than most liquid fueled rockets. The only match I know of is hypergolics, which are nasty toxic stuff. Plus, lack of precision isn't necessarily something that will always accompany solid rockets; a form of throttling could be only lighting off a few of of the multiple deorbit rockets, or sizing just one solid rocket based on the mission, which is compatible with the planning of a burn before the spacecraft leaves the ground that space agencies already deal with.

IIRC that's how it was done on Mercury missions.

 

[garyw]

-Of course you may be wondering how the hell the shuttle is supposed to deorbit. In the cavity left by the SSMEs, perhaps a solid fuel booster could be placed, also giving the shuttle a decent kick during an abort sequence too

So what do you think?

I was wondering how the shuttle is supposed to do any sort of manuever without some form of RCS or is the plan to keep the tank attached the whole time that the shuttle is on orbit?

As the fuel drains out of the ET the CoG will move towards shuttle so if the plan is to keep the ET attached once it's empty the RCS will induce a rolling motion and be very unstable.

 

[Donamy]

You still need RCS for reentry.

 

[Hlynkacg]

Remove everything in relation to solids on the space shuttle, make it an entirely liquid fueled design.

Why?

---------- Post added at 09:31 ---------- Previous post was at 08:55 ----------

Ok serious answer time

Moving both the RCS and the Main propulsion system to the ET defeats the purpose of having a space shuttle in the first place. That expensive Orbiter is now dead weight so you might as well delete it entirely and call your new launch vehicle SLS.

On a more constructive note there is something to be said for using the cheaper lighter J2s on the orbiter, and early STS designs did exactly this. They even included internal tank age so that the J2s could be used for orbital maneuvering. You should really look into the pre-shuttle STS designs, or just say "screw it" and build a Buran.

 

[Urwumpe]

-Tear out those blasted SSMEs, and use disposable engines, particularly J-2s. Using the J-2 design would work nicely by allowing the design to be off the shelf, and having a restartable engine would also allow a shuttle launch to launch to orbit with no payload, then act as a kick stage for some payload waiting up there. That does imply the next point to the design, since the Shuttle itself cant be going with the space probe

Everything, but not J-2 engines. These are for their thrust only slightly cheaper than a SSME over the life-time of a reusable SSME - no real game changer. Next, there are better technologies around, that could be used for replacing the SSME by something more economic.

Making a Full-Flow Staged Combustion Cycle version of the SSME would be a much better solution, but this is currently still experimental. But such a engine would operate at so low temperatures that a SSME replacement could operate for multiple hours, be cheaper (lower temperatures again) and still have a comparable performance (slightly lower specific impulse, because the fuel is colder when injected)

-Once youve torn out those engines, dont put the J-2 on the Orbiter, put it on the External Tank. This is a bonus because it reduces the number of parts that need to be checked/repaired/replaced at the end of the mission, and it allows for a second use of the engine & external tank after the Shuttle Orbiter has detached. It also might make more sense to move the RCS systems to the body of the ET, so that the stack can maneuver easily once in Orbit (closer to the CG, which I would figure would be somewhere right below the orbiters wings while attached to the big orange tank) and it removes a really tricky ground maintenance operation with the Orbiter (defuelling the RCS).

Makes the turn-around cheaper, but the construction more expensive. Instead of checking the engine between every flight, you have to check it during construction.

Also, the RCS then has to rotate 15 tons ET and be far away from the Center of Gravity. That is extremely stupid and means you also have to cut down payload mass for making the RCS work reliable.

-Of course you may be wondering how the hell the shuttle is supposed to deorbit. In the cavity left by the SSMEs, perhaps a solid fuel booster could be placed, also giving the shuttle a decent kick during an abort sequence too

Even a small such booster would weight a lot and be a safety risk by itself. The SSMEs and the fuel that flows to them weight about 15 tons. A 15 ton SRB could provide a lot of thrust, but not enough for dragging the orbiter to safety during an early launch abort. And later, it is just a useless dead mass that you have to carry with you. Especially during reentry, I don't want to have a SRM at the aft.

So what do you think?

I think you have not yet understood the Space Shuttle well enough to suggest sensible improvements. You don't make it better your way. You copy a Russian make-shift solution and think it was really better only by that. It wasn't. Buran had been better in many details, but you didn't locate these details in your improvements.

---------- Post added at 08:34 PM ---------- Previous post was at 08:30 PM ----------

Remove everything in relation to solids on the space shuttle, make it an entirely liquid fueled design.

Would be possible, but not automatically better. Additionally to what was already said: Solids are extremely economic engines. They have some drawbacks, but are extremely cheap for their thrust and impulse. A liquid booster replacing the SRBs would cost easily a multiple of a single SRB and be always more unreliable than a SRM, because SRMs don't fail. They can only perform too good for the vehicle.

 

[Pipcard]

So why does Energia have LRBs, then?

 

[garyw]

Because 4 x LRB's worked for Energia? Because the Russians don't have much expertise with solids unlike the US?

Also, energia only launched twice.

 

[Urwumpe]

So why does Energia have LRBs, then?

No experience with large solid rockets at all. While the USA focussed soon on developing large solid ICBMs and solve the technical problems with that, Russia decided to improve the storable propellant technology and with it, bipropellant technology as whole.

You can see that well if you compare the RD-0120 and the SSME. Or look closer at the NK-33. Technically miles more advanced than what the USA have ever considered in terms of bipropellant engines, but also with much lower complexity thanks to a better understanding of the behavior of the engines.

If you look at what Russian engines can do, you can get an idea, what would still be possible in the future for simple bipropellant engines. We have not yet reached the technical limit at all.

 

[garyw]

Russia decided to improve the storable propellant technology and with it, bipropellant technology as whole.

Wasn't that the whole dabbling they did with the devils venom?

 

[Urwumpe]

Wasn't that the whole dabbling they did with the devils venom?

Exactly. The Rockot or Dnepr launchers also still use it. While previously, the rockets had only been able to be fueled for a few days or weeks, the modern ones can be stored fueled for years.

 

[BruceJohnJennerLawso]

The idea remembers me the Buran design.

But I did not understand one thing: moving the RCS to the ET, you mean that the ET would be attached to the orbiter during the mission? This wouldn't limit orbital performance?

Yes, and I recall hearing that bringing an empty ET along wouldnt cut into payload much at all (maybe 5000 kg at the most?). The author of External Tank stations talked about it a lot.

[ame="http://www.orbithangar.com/searchid.php?ID=2067"]http://www.orbithangar.com/searchid.php?ID=2067[/ame]

Solid boosters for deorbit (which requires precision) and abort sounds risky. I don't think there's any way you can safely separate a big spaceplane that is sitting right next to two giant solid boosters, while those giant boosters are burning (separating those burning solids first would result in the tank and orbiter being engulfed in SRB exhaust).

Well the abort idea might not be that great, but as a deorbit stage, SRBs would be fine. They're often used on GEO missions as the final kick stage, since they're more reliable than liquid engines, and they can be stored for quite a while.

I was wondering how the shuttle is supposed to do any sort of manuever without some form of RCS or is the plan to keep the tank attached the whole time that the shuttle is on orbit?

As the fuel drains out of the ET the CoG will move towards shuttle so if the plan is to keep the ET attached once it's empty the RCS will induce a rolling motion and be very unstable.

You still need RCS for reentry.

Yeah, putting the RCS solely on the ET wouldn't be such a great idea, but there must be some way that a combined stack could be controlled. Was there ever any study done on how the shuttle would maneuver in orbit with the External tank attached? (ie for the purposes described above with the ET stations idea)

I think you have not yet understood the Space Shuttle well enough to suggest sensible improvements. You don't make it better your way. You copy a Russian make-shift solution and think it was really better only by that. It wasn't. Buran had been better in many details, but you didn't locate these details in your improvements.

Actually, I know virtually nothing about Buran beyond the basic info, but I just wanted to throw some ideas out there as to how the Shuttle could have been better. I'm not convinced that the core concept of the Space Shuttle is flawed, just that "1.0" had some design issues that held it back from being as good as it could have been.

You know, just about anything probably looks good when strapped to an Energia

 

[garyw]

Yeah, putting the RCS solely on the ET wouldn't be such a great idea, but there must be some way that a combined stack could be controlled. Was there ever any study done on how the shuttle would maneuver in orbit with the External tank attached? (ie for the purposes described above with the ET stations idea)

RCS and OMS on the shuttle would be sufficient. Once on orbit the tank doesn't weigh that much so maneuvering with the tank attached wouldn't be an issue. Having RCS just on the tank would be impossible due to the weight of the shuttle above it.

It's all to do with the CoG and how most of it is focused on the shuttle once the tank is empty.

 

[Urwumpe]

Actually, I know virtually nothing about Buran beyond the basic info, but I just wanted to throw some ideas out there as to how the Shuttle could have been better.

Yeah, but you will see me disagree on them, because they don't go into the right direction.

I'm not convinced that the core concept of the Space Shuttle is flawed, just that "1.0" had some design issues that held it back from being as good as it could have been.

There you will have me agree. The Endeavour was already one step further away from prototype status, but still had many issues to fix. The USA gave up improving spaceplanes too soon and became too content with what they had.

The hydraulics for example are one extremely bad part in the Shuttle design. The heatshield was also too complex.

You know, just about anything probably looks good when strapped to an Energia

How right you are. :rofl:

 

[garyw]

There you will have me agree. The Endeavour was already one step further away from prototype status, but still had many issues to fix. The USA gave up improving spaceplanes too soon and became too content with what they had.

The hydraulics for example are one extremely bad part in the Shuttle design. The heatshield was also too complex.

Agreed. There were many improvements on the drawing boards that ultimately went nowhere. Look at the glass cockpit upgrade and the SSPTS which is something that was an after thought. So much more that could have been done...

 

[Urwumpe]

Agreed. There were many improvements on the drawing boards that ultimately went nowhere. Look at the glass cockpit upgrade and the SSPTS which is something that was an after thought. So much more that could have been done...

Yes. And also many many small things, not just such big changes like the engine choice.

The EPS also lacked some refinement, that the shuttle was really depending on the fuel cells even in an emergency was not wise. Adding a small battery for at least being able to start a fuel cell again would have been a better choice, when you can't fly at all without electricity.

And the programming language of the Shuttle was also one part there, that made the Shuttle rather a prototype. While historically the right choice to develop HAL/S, today you would rather use Ada there. Ada already does a lot of the verification automatically that made the Shuttle software development so expensive.