SLS Shuttle

[Comrade Jenkens]

The whole point of a space shuttle is to bring back the SSMEs, which are the most expensive piece of the kit. If you are putting the engines on the core, then it simply doesn't make sense to have a reusable spacecraft.

Yet the space launch system uses 4 SSMEs and throws them away every time. Moving them from the shuttle to the main fuel tank would save weight on the orbiter and improve its dV.

[Nibb31]

The SSMEs that are used by SLS are paid for and have been amortized over 30 years. In other words, they are free, and you can't get much cheaper than that. So there is no point in reusing them.

The RS-25s that are supposed to go on the later SLS (if more than 3 ever fly, which I doubt) are designed to be cheaper than the old SSME design.

[Soda Popinski]

The SSMEs that are used by SLS are paid for and have been amortized over 30 years. In other words, they are free, and you can't get much cheaper than that. So there is no point in reusing them.

The RS-25s that are supposed to go on the later SLS (if more than 3 ever fly, which I doubt) are designed to be cheaper than the old SSME design.

The Shuttle program had to be cheap on a per launch basis, as it was intended to be launched very frequently. Hence the name "shuttle."

The SLS on the other hand is meant to launch infrequent big deep space missions. So reducing costs by savings SSMEs aren't as big of a deal.

Interesting tidbit, STS stood for "Space Transportation System," which would have had the shuttle, LEO space station, lunar space station, space tug, and a NERVA powered vehicle for transfering to lunar, GSO, or interplanetary trajectories. The only thing that survived was the shuttle.

[The Yellow Dart]

I don't know if you'll find this to be related or not, but have you hear of the Dream Chaser? I just found out about it yesterday. It is a small reusable space plane that sits on top of a rocket rather than attaching to the side, and can return to any conventional runway. It is for crew only, though, no large cargo bay or anything. I was just surprised I hadn't heard of it before now. They are already flight testing the prototype, and since the thing isn't really otherwise powered, besides orbital maneuvering thrusters, that is the main barrier to being used, really, just getting the aerodynamics right.

http://www.sncspace.com/ss_space_exploration.php

[hugix]

A shuttle radially attached to a SLS would not work. Attaching it to the third stage (or second or whatever) would make the thing really top heavy and unbalanced.

[jwenting]

Yet the space launch system uses 4 SSMEs and throws them away every time. Moving them from the shuttle to the main fuel tank would save weight on the orbiter and improve its dV.

that's one of the reasons it was fundamentally flawed, the whole idea of reusing major components was never achieved.

They also replaced a lot of the heat shields after every flight, rather than just a few tiles here and there.

Wasn't intended that way, but worked out that way.

[Nibb31]

I don't know if you'll find this to be relyated or not, but have you hear of the Dream Chaser? I just found out about it yesterday. It is a small reusable space plane that sits on top of a rocket rather than attaching to the side, and can return to any conventional runway. It is for crew only, though, no large cargo bay or anything. I was just surprised I hadn't heard of it before now. They are already flight testing the prototype, and since the thing isn't really otherwise powered, besides orbital maneuvering thrusters, that is the main barrier to being used, really, just getting the aerodynamics right.

http://www.sncspace.com/ss_space_exploration.phphttp://upload.wikimedia.org/wikipedia/commons/thumb/7/7a/Dream_Chaser_pre-drop_tests.6.jpg/800px-Dream_Chaser_pre-drop_tests.6.jpg

Of course we know about it. Every space geek has known about it for years.

Yes, it's reusable, but it's still functionally just a fancy reusable capsule on top of a disposable rocket. You still have to throw away the engines and tanks on each flight. The CST-100 capsule and Dragon capsule are also reusable, but the capsule is just a small part the vehicle. The big economical incentive comes from recovering the engines, not the crew compartment.

There is also the question of the cost to check and refurbish the vehicle between each flight. A spacecraft goes through a lot of physical stress: launch loads, landing loads, tanking, thermal cycles... The CST-100 for example is supposedly rated for 10 flights. Dragon is probably similar depending on required maintenance and engine rotations. We don't know how many times DreamChaser or any other spacecraft can be reused until the vehicles are thoroughly inspected after the first few flights.

Edited May 21, 2014 by Nibb31

[magnemoe]

I'm aware of Buran, but it's a totally different concept which was designed for use with the Energia from the beginning. Buran itself had no main engines which fired at launch, only its equivalent of the OMS. However the shuttle was designed with both the main engines and the OMS in the orbiter and only the fuel tank and boosters not on the orbiter. Buran was more of a payload, while the shuttle was part of the actual launch vehicle itself.

The only real differences to the shuttle I see on this concept would be a larger fuel tank with one more engine, larger boosters, letting the engines burn up instead of recovering them and even more structural forces and asymmetric thrust than the space shuttle already had. Needing to build completely new engines would result in higher launch cost(they already needed to be rebuilt partially, but the cost for that was still a lot less than building completely new ones). I don't see how this would get around the problems of the space shuttle program. Also the only advantage over the SLS that I see would be the ability to return something from orbit, but that ability of the space shuttle was rarely used.

Soviet at the time was not capable of making reusable rockets, secondary they saw that the large general shuttle was a mistake and designed the system as a very heavy lifter for other uses too.

However the return something was commonly used in the shuttle loads of missions with an lab in the cargo compartments instead of launching parts of an space stations and bring back samples.

[magnemoe]

that's one of the reasons it was fundamentally flawed, the whole idea of reusing major components was never achieved.

They also replaced a lot of the heat shields after every flight, rather than just a few tiles here and there.

Wasn't intended that way, but worked out that way.

The main problem is that adding more weight to first stage to let you recover it is 10 times less expensive than adding weight to the upper stage.

Something like an small shuttle or an large dragon pod on top of a first stage makes far more sense.

The shuttle was too stressed to achieve the goal they had to work it like a formula 1 car. Engine of a F1 car has to be rebuild after each run.

[Jouni]

The whole space shuttle paradigm simply doesn't make much sense at all. It was a great technological achievement and it was pretty, but it was a fundamentally flawed concept.

The concept wasn't flawed, only its implementation. Maybe NASA did some design mistakes back in 60s and 70s, or maybe the technology wasn't up to the task, but something similar might work in the future.

There were something like three main ideas in the Space Shuttle concept:

1. Reusable boosters. People still believe in that idea, and SpaceX apparently has figured out how to do it cost-effectively.
   
2. A large reusable multi-purpose orbiter that can carry a significant payload and a large crew to LEO, and stay in orbit for weeks. That might be a good idea, if we ever build more than just a few research stations in orbit.
   
3. Carry fuel in a disposable tank, while bringing the engines back with the orbiter. This is probably the most questionable part of the concept.
   

[Nibb31]

The concept wasn't flawed, only its implementation. Maybe NASA did some design mistakes back in 60s and 70s, or maybe the technology wasn't up to the task, but something similar might work in the future.

No the concept of a winged spacecraft is flawed. The wings, the landing gear and the hydraulics are all heavy, complex, and unnecessary.

The concept of a side-mounted launch vehicle is flawed. It adds a whole new set of failure modes and the thrust vectoring is inefficient.

[magnemoe]

The concept wasn't flawed, only its implementation. Maybe NASA did some design mistakes back in 60s and 70s, or maybe the technology wasn't up to the task, but something similar might work in the future.

There were something like three main ideas in the Space Shuttle concept:

1. Reusable boosters. People still believe in that idea, and SpaceX apparently has figured out how to do it cost-effectively.
   
2. A large reusable multi-purpose orbiter that can carry a significant payload and a large crew to LEO, and stay in orbit for weeks. That might be a good idea, if we ever build more than just a few research stations in orbit.
   
3. Carry fuel in a disposable tank, while bringing the engines back with the orbiter. This is probably the most questionable part of the concept.
   

The boosters had safety issues and cost of fixing them after splashdown was pretty much the same as making new ones.

Drop tanks are pretty common on fighter jets doing combat missions, might be that the shuttle tank was too expensive because cryogenic fuel and weight requirements.

Main issue was that to get the shuttle to work they had to stress everything to the limit, maintenance after flight was extreme. This both reduced the available launches but also made the shuttle to expensive to operate reducing the launches as it was only used for missions only it could perform this increased the costs of missions as its lots of fixed costs.

[Deathsoul097]

The idea behind the shuttle was sound but too many things kept being added into the design until it was just inefficient and poor at everything.

Also how did Buran stay balanced if its own engines weren't used for the accent?

Real engines have a LOT of thrust vectoring. (Though, the SSMEs had a lot, even for RL standards.) Something we are not so fortunate to have in-game. The engines on the Energia Core could gimbal about 8 degrees, IIRC, and being mounted inline with the rocket itself, it was not only more efficient, it had to gimbal less to keep stable, as more of the mass was inline with the engines. It also made the orbiter lighter when using it's OMS, which was also more inline with CoM, and thus more efficient and more easily manageable. While Buran in itself had a more than a handful flaws (Such as some Columbia-esque damage to the left wing on re-entry, which cause some warping) that needed to be worked out, it only flew one flight, so we cant really call it properly whether it was truly better or not. That said, I still think it was better and was, if not very close to, a space shuttle done right.

No the concept of a winged spacecraft is flawed. The wings, the landing gear and the hydraulics are all heavy, complex, and unnecessary.

The concept of a side-mounted launch vehicle is flawed. It adds a whole new set of failure modes and the thrust vectoring is inefficient.

I wholly disagree with your first point. Though a winged vehicle adds complexity, it also allows a very large range of possibilities, such as low G re-entry, which means that more fragile cargo and experiments can be transferred between on site in orbit and ground stations, and the ability to more easily control your point of return, in case anything goes wrong, to name two off of the top of my head.

I find myself kind of agreeing with your second point though. Side mounted, while the most Badass and iconic things there is, is quite an inefficient way of doing things, never mind the complexity of implementing it, which as you said, creates a whole new line of failures that could occur. It does have some benefits (Such as the ability to abort reasonably safely, to an extent, but this is only really applicable for the Buran, as the Space Shuttle was completely screwed if anything went wrong, as it was carrying the engines.), though I don't think they outweigh the downfalls. TBH, I think the best way to do it would be closer to what SNC is doing with Dreamchaser, or how the USAF X-37B is deployed. (Stack launch, winged return, and in the case of the X-37B, AFAIK, hidden inside a fairing. (Not sure about SNC's Dreamchaser, I've got no real foreknowledge about it.))

Edited May 21, 2014 by Deathsoul097

[Jouni]

No the concept of a winged spacecraft is flawed. The wings, the landing gear and the hydraulics are all heavy, complex, and unnecessary.

The concept of a side-mounted launch vehicle is flawed. It adds a whole new set of failure modes and the thrust vectoring is inefficient.

What if one of the billions of engineers who have not been born yet found a way to solve those problems? Would the concept still be flawed? If nobody can make something work, it only means that the people who are currently alive are not very bright. You need much more evidence to say that the idea is fundamentally flawed.

Besides, your second point has nothing to do with the Space Shuttle concept. It's just a technical solution people thought would be most convenient for launching a winged spacecraft.

The boosters had safety issues and cost of fixing them after splashdown was pretty much the same as making new ones.

Drop tanks are pretty common on fighter jets doing combat missions, might be that the shuttle tank was too expensive because cryogenic fuel and weight requirements.

Main issue was that to get the shuttle to work they had to stress everything to the limit, maintenance after flight was extreme. This both reduced the available launches but also made the shuttle to expensive to operate reducing the launches as it was only used for missions only it could perform this increased the costs of missions as its lots of fixed costs.

All of your points are technical issues unrelated to the Space Shuttle concept itself. The first one has almost been solved by advancements made after the development of the Space Shuttle. Powered landings seem to be a better way to retrieve used boosters than splashing them to sea with parachutes.

[Nibb31]

What if one of the billions of engineers who have not been born yet found a way to solve those problems? Would the concept still be flawed? If nobody can make something work, it only means that the people who are currently alive are not very bright. You need much more evidence to say that the idea is fundamentally flawed.

How could you make a winged spacecraft not as complex as an equivalent non-winged spacecraft? If you can figure a way to add wings, landing gear, and hydraulics without adding weight, then surely the same technology could be used to make non-winged spacecraft even lighter.

Besides, your second point has nothing to do with the Space Shuttle concept. It's just a technical solution people thought would be most convenient for launching a winged spacecraft.

The Shuttle's side-mount architecture was part of its fundamental design. If it wasn't side-mounted, then it wouldn't have been the Space Shuttle but some other vehicle.

All of your points are technical issues unrelated to the Space Shuttle concept itself. The first one has almost been solved by advancements made after the development of the Space Shuttle. Powered landings seem to be a better way to retrieve used boosters than splashing them to sea with parachutes.

You really need to clarify what you understand by "the Space Shuttle concept". For me, the Space Shuttle concept was the Vertical-Takeoff-Horizontal-Landing that NASA designed, which I think was a flawed concept. The main advantage of gliding to a landing was that it looked cool, and all through the 1970's, people were influenced by Buck Rogers and Star Wars. That is the main reason for wanting wings.

Powered landings were envisioned ever since people started dreaming about rockets. Look at some early 20th century sci-fi. Vertical landing was studied extensively with a whole bunch of experimental aircraft ever since the Convair XFY-1 all the way to Apollo LM.

[Jouni]

How could you make a winged spacecraft not as complex as an equivalent non-winged spacecraft? If you can figure a way to add wings, landing gear, and hydraulics without adding weight, then surely the same technology could be used to make non-winged spacecraft even lighter.

Complexity is just a price you have to pay, not a flaw in itself. The computer you are using is probably more complex than the entire Apollo program.

You really need to clarify what you understand by "the Space Shuttle concept". For me, the Space Shuttle concept was the Vertical-Takeoff-Horizontal-Landing that NASA designed, which I think was a flawed concept. The main advantage of gliding to a landing was that it looked cool, and all through the 1970's, people were influenced by Buck Rogers and Star Wars. That is the main reason for wanting wings.

I did it a few messages age: reusable boosters (a good idea), a big reusable multi-purpose orbiter (possibly a good idea), and bringing the engines back for reuse while disposing the fuel tank (not so sure). Those are all fundamental choices. We want to build a spacecraft that can do these things. We want to make it as reusable as possible. Fuel tanks are relatively cheap, so they can be discarded, if it's not feasible to bring them back. Things like shuttle attachment and horizontal landings are implementation issues.

Powered landings were envisioned ever since people started dreaming about rockets. Look at some early 20th century sci-fi. Vertical landing was studied extensively with a whole bunch of experimental aircraft ever since the Convair XFY-1 all the way to Apollo LM.

The difference is that powered landings are no longer a matter of study or sci-fi, but almost production-level technology.

[Nibb31]

I did it a few messages age: reusable boosters (a good idea), a big reusable multi-purpose orbiter (possibly a good idea), and bringing the engines back for reuse while disposing the fuel tank (not so sure). Those are all fundamental choices. We want to build a spacecraft that can do these things. We want to make it as reusable as possible. Fuel tanks are relatively cheap, so they can be discarded, if it's not feasible to bring them back. Things like shuttle attachment and horizontal landings are implementation issues.

Well we pretty much agree then.

Your definition is that of any generic reusable spacecraft. That's ok, and I guess it's an idea that makes sense*.

The Space Shuttleâ„¢ was an implementation of that idea. That implementation was fundamentally flawed.

* It's an idea that makes sense only if the economical environment makes it worthwhile to sustain a high enough launch rate. If you don't have enough payloads or customers, then a reusability is not economically viable.

[sgt_flyer]

Glided landings are useful for pinpoint landings (an apollo capsule usually splashed within a circle of a few km after reentry) - whereas a spaceplane will be able to land easily on a runway. - they are also much more gentle on the astronauts bodies / experiments (both during reentry and landing - less G forces)

[Nibb31]

There's no reason you can't do a pinpoint vertical landing. In fact, that's what SpaceX and Boeing are going to do.

You're right about the G-forces, but it's not worse than some rollercoasters than achieve 4 to 6 g. If you're not fit to ride in this, then you shouldn't be going to space in the first place:

http://youtu.be/cu2WnGRJT8k

[Armchair Rocket Scientist]

There's no reason you can't do a pinpoint vertical landing. In fact, that's what SpaceX and Boeing are going to do.

You're right about the G-forces, but it's not worse than some rollercoasters than achieve 4 to 6 g. If you're not fit to ride in this, then you shouldn't be going to space in the first place:

http://youtu.be/cu2WnGRJT8k

That 4-6 Gs only lasts for a few seconds though, while on a reentering spacecraft they would last several minutes.

That being said, capsules can already perform a pretty gentle reentry because they act as lifting bodies. I think Apollo is in the 4-6 G range, while Dragon is supposed to be capable of a 3.5 G reentry.

[Noah_Blade]

Hmm I do see what you mean, The shuttle could have had smaller wings which would mean bigger payloads (theoretically) but the US air force wanted it to do something with polar orbits (cant exactly remember) but then never really used it or took advantage of the bigger wings.

and the ISS is very inclined...

[tater]

Cool, a way to make SLS even more expensive/wasteful.

[Bill Phil]

One payload of SLS could be a spacecraft similar to the Orbiter from the Space Shuttle. But why on the side? It doesn't need to apply thrust at lift off, so it could go where all payloads should go: on top.

Really, the only Shuttle stuff being used in SLS is the tooling for the EXT, the SRBs (barely), and the RS-25s.

[78stonewobble]

Well, I suppose a return vehicle with wings, still makes some kind of sense for bring back capability of something expensive and/or large and/or heavy?

For you know, "outsized" cargo return capability.

The shuttle could bring around 14 tonnes back?

[wumpus]

The concept wasn't flawed, only its implementation. Maybe NASA did some design mistakes back in 60s and 70s, or maybe the technology wasn't up to the task, but something similar might work in the future.

There were something like three main ideas in the Space Shuttle concept:

1. Reusable boosters. People still believe in that idea, and SpaceX apparently has figured out how to do it cost-effectively.
   
2. A large reusable multi-purpose orbiter that can carry a significant payload and a large crew to LEO, and stay in orbit for weeks. That might be a good idea, if we ever build more than just a few research stations in orbit.
   
3. Carry fuel in a disposable tank, while bringing the engines back with the orbiter. This is probably the most questionable part of the concept.
   

"A large reusable multi-purpose orbiter" this should tip you off as a problem: large (aka massive) is everything you don't want in a reusable orbiter. The shuttle was designed to bring back a keyhole (presumably something Hubble-sized, thus the size of the cargo bay) back from polar orbit. Without that, it could simply use fairings like everything else and not need to bring up the heavy cargo bay (+ heatshield and everything else it cost) every time. Having the main engines in the orbiter was another major weakness, one that every other multi-staged vehicle avoids (unless you are using the "works in KSP" defence due to the deletion system). Older shuttle designs tend you use lower and upper "spaceplanes". This seems to be the difference SpaceX grabbed hold of, 90% of their rocket motors barely touch space and don't have to deal with full re-entry (and they aren't bothering with the other 10%).

As far as tossing the fuel tank, that seems to be a no-brainer. Unless you have a multi-stage rocket (and you should), that fuel tank is way to big to bring down. Just imagine trying to replace all the tiles on both the shuttle and the fuel tank (and carry all those tiles up as well).

As far as wings: I'm surprised that SpaceX doesn't use them. I wouldn't suggest shuttle sized wings, more like shrunken X-15 with barely a 1:1 glide ratio. Someone pointed out that such wings were originally designed for the shuttle and they had to switch due to hypersonic issues, so I suspect that they've moved past nearly all the low-lying fruit (such as parachutes). PS: In KSP, using a delta-deluxe winglet works great for bringing home a rocket with a couple of orange tanks and a mainsale. You will also need tailfins (or better yet, vertical stabalizers and airbrakes) as well (the cheap stuff has a <1000C temp range, so don't expect to use them).