Explain: What changed in Shuttle design that made it less effecient than intended?

[mellojoe]

I've heard numerous times that NASA's Shuttles ended up being massively less efficient than originally intended, and that it comes back to a design change somewhere in the process. But, I can't seem to find out what changed. What was the initial intent? Did it have something to do with the Main Shuttle Engines? Was it the wing design? From what I understand, the military demanded the wings to be as big as they were. Why was that?

Thanks.

[Rakaydos]

My understanding was the the shuttle was originally going to have a titanium or tungsten hull to withstand atmospheric reentry, but their budget got slashed halfway through, and they spent three times as much figuring out the foam glass heat shield they ended up with.

[astropapi1]

The military also required a bigger payloa ba, and that it was able to get into a polar orbit, so it was way more complicated than it needed to be for it's regular purpose.

[Nuke]

also the fact that you didnt just refuel the ship and launch it. they actually had to take all the engines out put em in a test rig and re-certify them between every mission. still i think the thermal protection system was still mostly responsible, since engine maintenance was expected to be a huge part of the refit cost. i also dont think they had as much success refurbishing srbs as they thought they would. frankly the shuttle had way to many disposable components, or components that are only guaranteed to work once. then twice you had disasters brought about by bureaucracy compromising safety, which no doubt resulted in more time being spent re-certifying parts of the shuttle.

[xenomorph555]

It was also meant to have a smaller cargo hold (1/4 of actual one), but the military intervened to make it bigger to launch spy satellites which they never did. Also the solid boosters were meant to be smaller and simple refuel but the larger ones they used had to be refurbished. The heat tiles had to be replaced every time. Overall it was cheaper to launch a saturn v then the shuttle...

[Brun]

The Shuttle ended up being very financially inefficient (i.e. it ended up costing more to operate than expected), in addition to technically inefficient, and it's this financial inefficiency that people often talk about when criticizing the shuttle. The biggest reason for the added expense is that the Department of Defense (which helped fund shuttle development and had considerable input on its final design) was expected to make regular use of the shuttle and, by doing so, partially subsidize its operations. When Challenger happened in '86, the shuttle fleet was grounded for over two years. This meant that several DoD payloads that only the shuttle could carry were also grounded, and that frustrated the DoD greatly. There were also other high-profile DoD launch failures around that same time (a Delta and 2 Titan failures, both carrying DoD payload), and combined with Challenger it really made the DoD worry about its ability to reliably deliver payloads to orbit, without long downtime caused by mishaps. So, the DoD bowed out and pursued their own launch vehicles. Without DoD money coming in the cost for all future launches went way up.

(Not to cast the DoD in a bad light here - they didn't just wait for the first mishap and bail on the shuttle program. The exact situation caused by the Challenger disaster had been something they had feared since the very beginning.)

EDIT: I know you asked about the shuttle's design specifically, but the operations side of things was also hugely important to the Shuttle's efficiency problems. While it was technically overdesigned for civil and science work, that alone didn't really kill the Shuttle's efficiency, since those tradeoffs were expected to be paid for by carrying DoD payloads. The DoD dropping out of the program is really what hurt it most, more than any single design aspect.

Edited April 22, 2014 by Brun

[mellojoe]

The military also required a bigger payloa ba, and that it was able to get into a polar orbit, so it was way more complicated than it needed to be for it's regular purpose.

I think this was the reason for larger wings, too, right? In order to bail out of failed launches from polar orbit attempts? In order to glide back to a usable runway?

[Simon Ross]

The large delta wing was simply to meet the USAF requirement for a large cross range capability during rentry

[astropapi1]

I think this was the reason for larger wings, too, right? In order to bail out of failed launches from polar orbit attempts? In order to glide back to a usable runway?

Yep, I forgot about that. They required a ridiculous cross-range capability, so the "flying brick" needed a delta wing.

[KASASpace]

Hmm, well:

The USAF wanted the ability to glide over 1,000 kilometers.

They also had spysats that were 60ft by 15 ft, and the shuttle's original bay was 12 by 40 (if I remember correctly.....)

So, bigger payload, polar orbits, more cross-range capability, and also the Shuttle External Tank. It was actually the largest cause for preventing quick(er) turn-a-rounds.

Not to mention the way too optimistic per year launch estimation.

Oh, and having a micro-budget given by Nixon.

[Nibb31]

From what I understand, the military demanded the wings to be as big as they were. Why was that?

Although the military requirements did nothing to make things easier, the real reason the Shuttle didn't work as intended is that paper rockets always work better than real ones. Engineering and physics will always make things harder.

This is a rule for all aerospace designs. They always end up overweight, overbudget and underperformance, which is why you always need to include margins in your basic design. This is also why things like Skylon are a pipe dream, because on paper its margins are so thin. Once you start cutting metal, testing always shows that things are less efficient as planned or that structures need reinforcing, or that a system needs more redundancy, etc... Once you've cut into your payload fraction, then your design no longer makes sense.

Any of those SSTO and TSTO designs that you see labelled as "Shuttle alternatives" were also based on thin margins. Once they would have entered the detailed study phase, all sorts of fundamental flaws would have popped up and they would probably have ended up with a similar compromise as what we got in the end. None of those alternative designs would have worked in real-life because a reusable spacecraft was such a tough nut to crack with 1970's technology, and still is.

[rkman]

The inefficiency is mainly due to a change in the application of the shuttle: instead of having a few launches per month as advertised in political circles, which would have reduced the per-launch overhead cost to acceptable level, it did only a few per year. http://en.wikipedia.org/wiki/Criticism_of_the_Space_Shuttle_program

[Nibb31]

The inefficiency is mainly due to a change in the application of the shuttle: instead of having a few launches per month as advertised in political circles, which would have reduced the per-launch overhead cost to acceptable level, it did only a few per year. http://en.wikipedia.org/wiki/Criticism_of_the_Space_Shuttle_program

And of course, at the time, everybody at NASA knew that the advertised launch rate was intenable...

It wasn't less efficient than intended, because it was never really designed to launch 50 times per year.

Edited April 22, 2014 by Nibb31

[rkman]

Not so sure about everybody at NASA, given that a couple of years later NASA management would go on the record claiming a 1 in 1000 chance of mission failure.

Not doubt more than a few at NASA knew the advertised launch rate was unrealistic, but not everyone at NASA gets to talk to politicians.

[Umlüx]

now this is an interresting topic. putting all those additional requirements aside.. the large bay, the cross range capability... how would the shuttle actually look if nasa built one simply to their own requirements?

[Nibb31]

now this is an interresting topic. putting all those additional requirements aside.. the large bay, the cross range capability... how would the shuttle actually look if nasa built one simply to their own requirements?

Before the DoD got its grubby hand into the STS program, Max Faget was the guy in charge, and it was leaning towards a reusable TSTO design with stub wings. It was nicknamed the "DC-3", because of those wings. On some of the iterations, those wings were retractable.

http://www.astronautix.com/lvs/shuledc3.htm

Type "Faget Shuttle" in Google and you will find all sorts of pretty pictures of the "DC-3" concept. Take it all with a grain of salt though... There's no reason to believe that Faget's shuttle wouldn't have had the same problems that the actual STS had, or even worse. It probably wouldn't have been capable of reaching orbit at all.

Edited April 22, 2014 by Nibb31

[Moar Boosters]

It wasn't just the military requirements that caused problems. Originally it was supposed to service a huge NASA space-station. The plans for the station were postponed and eventually cancelled, so it quickly became apparent the orbiter was going to have to do a lot of the tasks the station was supposed to perform.

This meant the design got much bigger.

[NeoMorph]

It was also meant to have a smaller cargo hold (1/4 of actual one), but the military intervened to make it bigger to launch spy satellites which they never did.

Ummm... How do you know they didn't. For example, look up STS-51C.

I think they launched at least one Keyhole spy sat...

Edited April 22, 2014 by NeoMorph

[xenomorph555]

Ummm... How do you know they didn't. For example, look up STS-51C.

Oh sorry, launch on a lots of them on a large scale.

[jwenting]

the original idea could have worked. But by the time the design by committee was complete it was a major miracle it was able to lift off at all...

[Mazon Del]

It wasn't just the military requirements that caused problems. Originally it was supposed to service a huge NASA space-station. The plans for the station were postponed and eventually cancelled, so it quickly became apparent the orbiter was going to have to do a lot of the tasks the station was supposed to perform.

This meant the design got much bigger.

I think the station you are mentioning is actually the canceled second half of the ISS. The ISS was supposed to be (and mostly is) a research platform that housed astronauts. However, the astronauts in question were primarily going to be the workers at a second station right next door (only several hundred meters away) which was to be an orbital dry dock for construction of ships. Dry dock in this case being somewhat the opposite, in that it was meant to fill with air so the crew could work on the ship without suits. The two stations were never supposed to be connected because they didn't want the vibrations of the industrial processes going on to interfere with the experiments on the primary ISS.

[NeoMorph]

Oh sorry, launch on a lots of them on a large scale.

Ahhh... gotcha...

Some of those early lifting bodies look a lot like Spaceship One (and Two). The big difference was the new material science that makes the body so much lighter. The Shuttle on the other hand turned into nothing more than a flying brick...

Most of the Astronauts from the Mercury/Gemini/Apollo hated shuttle. They called flying it nothing more than being a bus driver. So I'm betting they did everything in their power to make it suck more so it would fail lol.

Seriously though, America lost its way in the space race... It's like they got to the the moon and said.... "WE WON... but there isn't anything here... let's go home" and just lost the plot.

Now China is storming ahead... and with all the tech they have bought, stolen and invented, they are in a really strong place. The US on the other hand don't even have a man rated launch spacecraft.

Did the shuttle overcosts, poor design (due to penny pinching bureaucrats) and disasters actually kill the US space program? Personally I think it did. And Obama finished it off.

[cm2227]

Overall it was cheaper to launch a saturn v then the shuttle...

I disbelief that, as a Saturn V cost around 1.2 billion in todays money. But still, it was way more expensive.

Adding to the cost was the experience with reusable engines. Before the shuttle, all liquid fuel engines were sometimes fired several times, they were still designed as disposable. Over the years NASA found out how much has to be refurbished and checked in the SSMEs. This was just not compatible with the intended recycle times during flights.

Also, the shuttle was not as appealing to commercial satellite launches, even before STS-51L. After the Challenger disaster NASA didn't want commercial operation any more, as the spacecraft was considered too risky and valuable to wager it on a tv satellite.

[Rakaydos]

Did the shuttle overcosts, poor design (due to penny pinching bureaucrats) and disasters actually kill the US space program? Personally I think it did. And Obama finished it off.

Didnt NASA get a biigger budget this year than in the last few administrations?

I mean, it's not like there's been a war on or anything to distract people...

[Moar Boosters]

I think the station you are mentioning is actually the canceled second half of the ISS. The ISS was supposed to be (and mostly is) a research platform that housed astronauts. However, the astronauts in question were primarily going to be the workers at a second station right next door (only several hundred meters away) which was to be an orbital dry dock for construction of ships. Dry dock in this case being somewhat the opposite, in that it was meant to fill with air so the crew could work on the ship without suits. The two stations were never supposed to be connected because they didn't want the vibrations of the industrial processes going on to interfere with the experiments on the primary ISS.

The space station plans go as far as the proposals for the shuttle itself.

After the apollo plan, NASA decided they had 4 options. A manned mission to mars, a followup moon program, an orbital infrastructure program, or discontinuing manned spaceflight.

They went with the orbital infrastructure program, but it was decided that it'd cost too much to develop the station and the shuttle at the same time. Their plan was to build the shuttle first and then use that to construct the station, however it soon became apparent the space station was never going to happen, so they had add lots of life support and science capabilities to the shuttle so it'd be capable of more than just dropping people off at a station.