Discussion Space Shuttle in Retrospect

[Urwumpe]

There you are, the Saturn could have gone on for longer, maybe using less "budget intensive" launches like two a year instead of six to match the Space Shuttle.

Sorry, but you are arguing with blind faith, not with facts. Like your LEM is like a ISS module stuff - if things would be that easy to do, we would already fly to the center of the galaxy to tap our energy off it.

In reality, things have costs, schedules and requirements.

Do you know why the VAB has four high bays? Not because this adds symmetry. The Saturn V simply needed so long for assembly and integration tests, that using only one high bay would have meant much lower flight rates than it already had.

Also, have you ever bothered to look at the old videos how work was like back then? The Saturn V required hundreds of people working at the pad for getting ready for launch. People that also cost a lot of money, since you can't just lay them off between launches. The many different connections and systems at the launch pad, everything had to be operated and checked manually. Automated tests like the Shuttle has had not been possible with Saturn, only for later updates, automatic testing environments got researched - which the Shuttle received already early in its design process. Any Saturn V update (the Saturn V was essentially done by 1962 technology) would have required more and more workarounds that increase workload - only a real clean sheet redesign like the Shuttle had a chance at all to incorporate also the many tiny details for cheaper processes on the ground (yes, as funny as it sounds), that made it cheaper than the Saturn V.

Take for example something as trivial as loading the payload while the shuttle is already on the pad. The Saturn V was unable to do so, it needed the payloads to be installed on the pad. Idiots like to say that the RSS was just an air force requirement to installed payloads secretly, but that is wrong: Any good economic launcher today is like the Shuttle, designed to accept the payload as late as possible and permit work on the payload until late into the launch countdown. The shuttle has the advantage that the payload hangs way lower on it and can be accessed with simpler processes - which save time and money.

Also, the space shuttle made good use of Apollo technology anyway, do you really think it was "everything new, forget Apollo"? The Space Shuttle took the best of Apollo for it. And added stuff that no update could have added.

Really: Stop treating Apollo like it was the holy grail of spaceflight. They only landed on the moon. Not more, not less. Even Apollo astronauts envied the Shuttle astronauts because they got a spacecraft that permitted them to do much more in space, as it was possible with the Apollo program.

If you care about the economics and technology, Apollo was even way more primitive than Gemini. Simply because Apollos design was frozen already before Gemini was even started.

---------- Post added at 08:41 PM ---------- Previous post was at 08:39 PM ----------

Yes, that is actually what I am actually trying to point out. The Space Shuttle needs crews, the Saturn does not.

Yes, and? The crew is the primary payload. How many spacecraft in the world can currently carry a crew of seven astronauts?

Without manned missions around it, the Saturn V would have been completely not affordable.

 

[Scruce]

Ok, I'm in error when comparing the Space Shuttle to the Saturn V and saying that the Space Shuttle is "all better". It's not, the Saturn was the "brute force to the Moon" option, It's not suited to the general applications option that the Space Shuttle had provided.

But, in my new opinion, something other than continuing Saturn or starting the Space Shuttle would ultimately have been better.

While the system was developed within the original cost and time estimates given to President Richard M. Nixon in 1971, the operational costs, flight rate, payload capacity, and reliability have been much worse than anticipated.

In order to get the Shuttle approved, NASA over-promised its economies and utility. To justify its very large fixed operational program cost, NASA initially forced all domestic, internal, and DoD payloads to the shuttle. When that proved impossible (after STS-51-L), NASA used the ISS as a justification for the shuttle.

The Shuttle program is flawed. Achieving a reusable vehicle with early 1970s technology forced design decisions that compromised operational reliability and safety. Reusable main engines were made a priority. This made it necessary that they did not burn up upon atmospheric reentry, which in turn made mounting them on the orbiter itself a seemingly logical decision. However, this had the following consequences:

• A more expensive 'clean sheet' engine design was needed, using more expensive materials, as opposed to existing and proven off-the-shelf alternatives (such as the Saturn V mains);
  
• Increased ongoing maintenance costs related to keeping the reusable SSMEs in flying condition after each launch, costs which in total may have exceeded that of building disposable main engines for each launch;
  
• Less absolute tonnage available to be lifted into space, since the mass of the SSMEs attached to the orbiter necessarily cut into the craft's 'payload budget' (more payload launched at any one time, by definition, reduces launch costs per pound).

The Space Shuttle is over now, we've learned new information out of it that we can use in new NASA projects. Such as that what lies in the head can change drastically in reality.

Original vision of ground processing of the Space Shuttle:

And what it turned out to be:

Things what the Space Shuttle was designed for, but later changed:

• NASA's initial policy of using the Shuttle to launch all unmanned payloads declined , and eventually was discontinued. ELVs proved much cheaper and more flexible.
  
• Following the Challenger disaster, use of the Shuttle to carry the powerful liquid fueled Centaur upper stages planned for interplanetary probes was ruled out for Shuttle safety reasons.
  
• The Shuttle's history of unexpected delays also makes it liable to miss narrow launch windows.
  
• Advances in technology over the last decade have made probes smaller and lighter. As a result, robotic probes and communications satellites can now use expendable launch vehicles, such as the Delta and Atlas V, which are less expensive and more reliable than the Shuttle.

Also, I don't believe that Apollo was "the holy grail of spaceflight", Gemini probably would have been the better option to get to the Moon ([ame="http://www.orbithangar.com/searchid.php?ID=213"]as described here[/ame]).

But as the title of the thread says: The Space Shuttle in Retrospect, should we attempt something like the Space Shuttle ever again?

In the year 1972, the Space Shuttle seemed like a great idea, we now know that the Space Shuttle was a failure that we had to learn from.

 

[Urwumpe]

It has to be said: This "Original vision" is done by an artist, who never even bothered about engineering. The original Shuttle design documents had been much closer to the reality like it is now.

And hell yeah, we should do something like the Shuttle again. Attempt the impossible to achieve the possible.

It must not do everything like the Space Shuttle, but many important aspects of it are too good to ignore. Like its payload bay being optimal for EVA work. The ISS is pretty good there, but too confusing in its size and shape to be a good EVA "playground" like the Shuttle was.

 

[T.Neo]

Yes, that is actually what I am actually trying to point out. The Space Shuttle needs crews, the Saturn does not.

AFAIK the only thing STS needs a crew onboard for is to activate things like landing gear and air data probes on landing.

Of course, there was also the Remote Control Orbiter cable that could remove the need for a crew onboard to accomplish these tasks. So STS could really be operated remotely, it's just that the hardware did not always exist.

I agree, partially; for some payloads, human presence is not necessary, and thus human presence will increase costs.

But from a payload standpoint... STS actually had a useful payload size. Saturn did not.

STS only had pretty bad GEO/BEO performance, because it never flew with the high performance, cryogenic stages that were originally intended to fly on it.

But, in my new opinion, something other than continuing Saturn or starting the Space Shuttle would ultimately have been better.

I tend to agree, but the question of "better" has no single answer.

Even the shuttle program that we had, with some small changes or improvements (that were proposed but sadly did not occur), would have been better.

flawed. Achieving a reusable vehicle with early 1970s technology forced design decisions that compromised operational reliability and safety. Reusable main engines were made a priority.

Not all engines are created equal. The SSME is a high performance, complex, staged-combustion beast. Its technical nature obviously impacts its reuse.

Perhaps if an engine like the J-2 were chosen as the SSME, it would have been more successful reuse wise. And they were also continuously increasing the throttle rating of the SSME, which puts it under even more stress.

For example, Pratt & Whitney gives figures for their Common Extensible Cryogenic Engine of 10 000 seconds service life and 50 in-space starts.

That is enough for some 20 flights, including a two-burn trajectory. Now imagine what you could do, if you could buy a $30 million engine, and reuse it 20 times with just cheap recertification checks on the ground in between flights?

Less absolute tonnage available to be lifted into space, since the mass of the SSMEs attached to the orbiter necessarily cut into the craft's 'payload budget' (more payload launched at any one time, by definition, reduces launch costs per pound).

Placing engines on the core instead of the vehicle gives you a minimal saving mass-wise, because it almost goes all the way to orbit.

All launch vehicles carry some engines to the final payload deployment. Including Saturn.

 

[_Designer_]

I understand that the program is 35+ year old technology still in use with technology booming all around. I cannot wait to see the new spacecraft once developed. Maybe we'll be able to go to mars soon.

besides, looks like we'll have faster-than-light-travel soon *crosses fingers*
http://www.reuters.com/article/2011/09/22/us-science-light-idUSTRE78L4FH20110922

 

[Saturn V]

The bottom line is, no matter how vehemently we argue "what might have been," there's no telling where follow on development to the Saturn might have gone. It's all conjecture.

There is far more history and evidence (for and against) of the Shuttle's accomplisments simply due to the longevity of the program.

Yes, the objectives for the Shuttle changed significantly...even after it started its operational life.

The U.S.S.R./Russia had 25 years worth of experience with space stations (compared to the few months Skylab was flown with a crew aboard) before the shuttle was tasked with crew transfer/ resupply duties for MIR & the ISS. Technologically, they didn't really need our help (IIRC, the core module of MIR was launched just a few weeks after the Challenger disaster). They'd done just fine all those years without us. Financially, it's another story. And yes, it made sense for both parties to pool resouces and share the cost. And yes, there were tremendous strides forward made possible by the collaborative effort.

But use of the Shuttle to perform those functions was an afterthought. The Shuttle was an abject failure as a commercial venture. And yes, it WAS dangerous. ALL manned spaceflight is, and will continue to be. Let's not forget, people died in Apollo too. The fact that they never left the ground is irrelevant. They died aboard an American spacecraft.

For all their shortcomings (political, social or financial), both programs had their successes & failures.

But in terms of grandeur, lighting the imagination and generating interest in the long term exploration of space, 4 decades in LEO just wasn't doing it.

Regardless of its merits, the Shuttle program made space seem rather boring to "John Q. Public."

Ultimately, NASA will be remebered as the agency that put a man on the moon, NOT the agency that flew the Shuttle.

 

[Urwumpe]

Every spaceflight is dangerous. You can even die far away from any launch complex, when a satellite part falls on your head.

 

[Eli13]

Every spaceflight is dangerous. You can even die far away from any launch complex, when a satellite part falls on your head.

But... but... but what about sharp edges?

 

[GoForPDI]

I'm afraid I can't vote on that poll. I seriously doubt that Mars could have been achieved directly after Apollo if the full Apollo Applications Programme had been pursued rather than STS.

The 30 years of Shuttle service will have done more in terms of Mars preperation and training than continuing the Saturn production. Shuttle pretty much drilled in new ways of doing spaceflight, whether that is crew training (Skill based vs. Mission based training), robotics, EVA, assembling spacecraft in orbit, working with international partners, spacecraft design, crew safety, ground infrastructure... the list goes on and on and on and on and on....

The things I listed above are all very difficult, but necessary pieces of technology and know how that are needed for a Martian excursion. A Mars mission would not have been possible without the thirty years of lessons learned and the technology developed during the era of STS, Mir and ISS.

I'm not saying STS was perfect either, its commercial satellite and military applications were much better suited to unmanned launchers and spacecraft, but, the experience gathered in the past 30 years (as well as the many benefits with regards to science and international cooperation) is absolutely crucial to any future efforts.

But then, how am I to know what happens in an alternate timeline?

 

[Cras]

There is a great work of alternative history, Voyage by Stephen Baxter where the United States does in fact decide to not persue a reusable Space Shuttle, and instead sticks with the Saturn technology and goes to Mars. Good read, shows a very good technical view on what it would have been like. I recommend it to everyone interested in manned space flight.

But there is something to be said for the Shuttle program being fundamentally different from what Saturn represented. The Shuttle was designed to make LEO routine, be cheap to launch, be incredibly safe, carry huge crews, not require the crew to wear pressure suits during launch and re-entry, be able to carry that huge crew along with a huge payload, build a space station, and of course be reusable.

Obviously the Shuttle failed a lot of those objectives. It quickly lost its appeal as a means to launch commercial payloads, the DoD lost interest in encrypting the systems for their classified flights, and Challenger gave them cold feet. The Shuttle quickly proved to not be nearly as safe as it was supposed to be, and that in turn made it incredibly expensive to launch and fly in orbit.

But the fundamental ideas, or I would even hazard to call them ideals, is the payload bay, the resuseability, landing on a runway, not splashing down in the ocean, the large crews, the airlock so EVA could be performed and not required the whole cabin to be depressurised. I would have loved to see, and still wish for, a second generation shuttle, where the mistakes learned from the first fleet are incorporated with modern technologies. A Shuttle MkII would be one heck of a machine.

 

[T.Neo]

But the fundamental ideas, or I would even hazard to call them ideals, is the payload bay, the resuseability, landing on a runway, not splashing down in the ocean, the large crews, the airlock so EVA could be performed and not required the whole cabin to be depressurised.

All of those things can be done by other vehicles. Ok... so what STS does that those vehicles cannot do, is do all of those things together.

But maybe there are other combinations of capabilities, that could also be useful... :hmm:

 

[Cras]

All of those things can be done by other vehicles. Ok... so what STS does that those vehicles cannot do, is do all of those things together.

But maybe there are other combinations of capabilities, that could also be useful... :hmm:

I would agree that we do not need a manned vehicle with that size of a payload bay anymore, unless NASA has a plan to build another LEO space station.

If I had the magic wand and was to design a Shuttle MkII, I would sacrafice that payload bay for more crew space. Larger crews, longer duration flights, more protection for higher altitudes, those would be my goals for a next generation Shuttle. I have more fantastic desires for such a project, such as the ability for it to be used for ferrying people to a lunar surface station and back, but that is not something I would consider "realistic", more just wishful hope that something like the XR2 could exist in real life. :thumbup:

And rethink the whole umbilical external tank buisness. SRBs are dangerous enough, the umbilical external tank feeding the shuttle mains on the orbiter is too much. A second generation shuttle I would envision would have engines on the tank somehow. That would most likely mean it would be require one use engines, which I don't like the idea, I would prefer to build on the reusability factor, but the thing should also come closer to what STS's goals were, cheap launches, safe launches, and quick turnaround for 50 launches a year.

 

[zerofay32]

http://beyondapollo.blogspot.com/2011/04/jscs-shuttle-ii-1988.html

Shuttle II 1988

I don't think it got very far, maybe Phase 0, but interesting reading regardless.

EDIT: The above page makes reference to a NASA Langley Research Center Shuttle II proposal as well, here is a site that talks about it.

http://www.pmview.com/spaceodysseytwo/spacelvs/sld051.htm

 

[T.Neo]

I would agree that we do not need a manned vehicle with that size of a payload bay anymore, unless NASA has a plan to build another LEO space station.

I don't like the idea, that the only way to build a space station, is the "shuttle way".

For example: what about a vehicle, that can be configured for cargo only, crew only, or a bit of both? Why should it be so impossible, for example, to have one vehicle approach a manned complex automatically, dock, transfer its cargo, and then have that cargo integrated with the greater structure by another vehicle carrying a crew and any necessary EVA equipment?

If I had the magic wand and was to design a Shuttle MkII, I would sacrafice that payload bay for more crew space. Larger crews, longer duration flights, more protection for higher altitudes, those would be my goals for a next generation Shuttle.

To be honest... I do not see the point of hauling an extra 20 people into space. Maybe it is just ignoring the possibility, because it does not yet exist... but I think it would be less useful than your average shuttle payload, and average shuttle crew size.

But flexibility- keeping that ability in the design, would definitely be a nice thing to have. As far as I know, this was discussed somewhat with STS, but obviously never implemented.

Personally, what I would do is keep a crew size of 8-10 people, and attempt to vastly improve the abort and escape options available to them. STS was sold as being too safe to require an abort system, but this ended up being hubris. The crew had no means of abort in the first 2 minutes of launch, nor did they have a way of surviving catastrophic failures.

I have more fantastic desires for such a project, such as the ability for it to be used for ferrying people to a lunar surface station and back, but that is not something I would consider "realistic", more just wishful hope that something like the XR2 could exist in real life.

:lol:

Ah yes... but the difference between an XR2-like shuttle, and a real shuttle, is that the latter could get people to the Moon... but it would be used to construct the lunar transport infrastructure in space, rather than be used to directly travel to the Moon.

It was quite an interesting idea, but unfortunately not one that ever ended up being tested out.

And rethink the whole umbilical external tank buisness. SRBs are dangerous enough, the umbilical external tank feeding the shuttle mains on the orbiter is too much. A second generation shuttle I would envision would have engines on the tank somehow. That would most likely mean it would be require one use engines, which I don't like the idea, I would prefer to build on the reusability factor, but the thing should also come closer to what STS's goals were, cheap launches, safe launches, and quick turnaround for 50 launches a year.

I don't really think that propellant crossfeed to the Orbiter caused any problems, in 135 flights. I may be wrong, but as I understand, the only major safety issue relating to the ET was the fact that it created TPS-damaging debris.

I would prefer to reuse the engines. But a different reuse strategy for the engines- for example, to use lower performance, almost "dumbed down" engines, that you could say fly 20 or so times, with minimal maintainance in between, might be a better reuse strategy.

Or at least: it would be interesting to try. And that is where the "lower technological risk" expendable core stage engines are inferior; it doesn't allow for that development/research factor.

Or, you could actually try integrating the propellant tank and the vehicle. Make a true two-stage vehicle, rather than a 1.5 stager like the Shuttle... :hmm:

 

[Urwumpe]

NASA is investigating making a kind of hydrogen/oxygen engines that run by using full flow staged combustion. This is similar to the staged combustion in the SSME, but instead of just the exhaust gases of the gas generator/preburner, the full propellant flow (either LOX or LH2) runs through the turbine after being mixed with the gas generator exhaust.

This results in much lower temperatures at the turbine at almost the same energy as in staged combustion - which permits with the higher mass flow slower turbine RPM and temperatures with the same power available for the turbopumps. Which in turn increases the lifetime of the engine a lot, possible would be multiple hours of accumulated burn-time, if the technical problems of mixing steam and cold fuel could be solved (Namely you requiring a minimal mixture ratio between gas generator mass flow and total mass flow, so the steam does not result in ice)

 

[Saturn V]

Unfortunately, the concept of cheap AND safe appear to be mutually exclusive.

The idea of having to accept one at the expense of the other is irrational, but it is the reality.

Look at the airlines' safety record after deregulation. We got cheap alright (anybody else remember Peoples Express and NYC - Orlando fares of $39?). But at the expense of proper maintenence, overworked, unqualified crews, improperly stored equipment, "convertible" 747s flying into Hawaii, etc.

And now fares have gone back up significantly. Almost to pre-deregulation rates. But has safety increased comensurately? No. They're still cutting corners because their overhead is so high. The fare increases are chalked up to rising fuel costs, so you're still SOL if you think you're getting anything more in terms of safety along with those fare hikes.

Challenger was risked because of the $$$ the schedule slippages were costing. Even though NASA & Thiokol were warned of the risk by Rodger Boisjoly, they took the chance and we all know how that played out.

So Shuttle operations became safER (at avery real and appreciable cost, of course). But by it's very nature, I don't believe you will ever be able to eliminate the risk of spaceflight...at any cost. The astronauts (and cosmonauts) have to accept that trade-off or they'd never fly those machines in the first place.

 

[T.Neo]

I think you can settle on a design strategy that is both cost effective and reliable. Indeed, a cost effective vehicle can be reliable based on its simplicity.

Of course you still need high quality control, safety checks, etc, and those cost money. But that is no reason to go for the costliest, most ineffective vehicle you can find, just to make things worse.

As far as I can understand, the inherent safety issues of STS were related to two things:

1. Lack of proper abort capability, especially in the first 2 minutes of flight.

2. TPS fragility and inherent debris problem caused by ET insulation.

Maybe TPS fragility was more of a maintainance issue. The safety issue came when they underestimated the potential for damage and LOV/LOC potential. And even then, a rescue mission would be possible technology wise... but facility wise and schedule wise, that is a different story.

At least the ISS could then be used as a "safe haven".

But the advantage of any "evolved spaceplane", would hopefully be a healthy enough flight-rate, that a crew stranded in orbit due to a critical failure, could be "easily" rescued.

 

[Saturn V]

As they say, "the Devil is in the details."

Cost Effective and cheap are 2 different things (and probably highly subjective as well).

 

[Cras]

The umbilical ET tank mostly showed its ugly face on the ground with launch scrubs, and it seemed like every launch near the end of STS (Aside from STS-135 it seems which was a near flawless and dramatic launch) there was some issue or another with the umbilical connections. However you are right, it never seemed to pose an issue during flight, but the true issue with the ET was that damn foam falling and smashing into the Orbiter.

My thought on bigger crews is bigger is better, as is the flexibility that you can actually do it. A 8-10 crew probably would have been a nice thing to have in the later days of the shuttle, Shuttle only could fit a max of 7 for a normal mission. I always look at if there is ever a time when we have a lunar surface base, being able to shuttle large crews to and fro would not be such a bad thing. It certainly would limit the other things that could be done with the vehicle, relegating it to pure shuttle and not the psuedo-space station that the STS orbiter actually was, this big floating base in space.

Shipping 20 astronauts to the moon at one time would allow a nice crew rotation (assuming the surface base itself can sustain a nice big contigent at a time as well), and also send some support along with it. Meaning, have a CDR and PLT go along that will not stay on the moon, some other mission specialists that will assist with the craft and any other duties such as unloading cargo or specially trained for an EVA repair, or what have you, then also have the large crew rotation, all at the same time.

I have stated before I think the Shuttle based ISS construction was a very good idea. The concept of module and the crew to install it being launched on the same vehicle is just very appealing to me. But the same sort of thing or the moon, be it ground base or lunar orbital station? then it no longer makes sense to me, so that is one reason I would not be sadden to see a hypothetical Shuttle MkII lack that very large payload bay.

But everything else that went with the payload bay I do like, the robotic arm, the OBSS, the docking port and airlock (if there is one thing that gets me to shake my head is why so many add-ons insist on a retractable nose cone to reveal a docking port.)

 

[Urwumpe]

The tank problems during the last launches had been caused always by things, that can happen to any cryogen bipropellant rocket system. The side-mount was not causing it.