Ridiculous space technology question

[PeZook]

This is probably a dumb question, but I just thought of something...

The STS (space shuttle) is essentially a space booster which carries a payload of about 112 tonnes to LEO (if we count the orbiter as payload). The Apollo+SIVB stack which went to the Moon weighed around 120 tonnes.

So...

So...

Why the hell is NASA developing an entirely new rocket to fly to the Moon? And doing it while maniacally trying to employ Shuttle technology to keep the workforce employed? Sure, an actual flight to the moon would need a new third stage instead of the orbiter, but...

As I wrote, it's probably a dumb question, but intriguing.

[Solauren]

To justify their budget.

That's why alot of stupid things occur in any government agency.

[PeZook]

To justify their budget.

That's why alot of stupid things occur in any government agency.

They could do that by developing the new STS-based moon-ship, too. There's got to be something more to it.

...or blinding incompetence.

[NecronLord]

You mean, why not just bolt a lunar third stage onto the ET and SRBs? For a start, I expect that the ET is configured for a fairly specific distribution of mass on the orbiter. Which is just fine for a re-usable 'space truck' design that's standardised. A lunar rocket, on the other hand, could be called upon to transport a number of different missions, depending on the intended permanance of a prescence.

What's more, your lunar vehicle would then have to do the work of a second stage, running off the shuttle ET, which means you've got to sacrifice some space on the orbiter to house engines that run off the (jetissoned) ET. Or put a rocket engine on the ET... at which point you're basically designing a new vehicle anyway, so why not go with what's known to work for this mission, and build a bigger, better, updated Saturn 5?

The shuttle gets benefit from the ET arrangement because it's a re-usable design, and it preseves the actual engines of it uses to consume the ET's fuel. I don't think there's any idea that the new lunar vehicle will be re-usable, so why not just put the rockets on the ET, and jettison the engines? It'll all get burnt up anyway. By putting the second stage engines on the vehicle itself, that just means towing extra mass to the moon, and would increase the fuel cost needed to make course corrections and so on.

I'm not able to find any detailed information offhand on the deltaV of the shuttle's disposable components. But I would seriously consider that the whole apparatus might not be able to provide equivalent deltaV to the Saturn V's first two stages, too.

[GrandMasterTerwynn]

This is probably a dumb question, but I just thought of something...

The STS (space shuttle) is essentially a space booster which carries a payload of about 112 tonnes to LEO (if we count the orbiter as payload). The Apollo+SIVB stack which went to the Moon weighed around 120 tonnes.

So...

So...

Why the hell is NASA developing an entirely new rocket to fly to the Moon? And doing it while maniacally trying to employ Shuttle technology to keep the workforce employed? Sure, an actual flight to the moon would need a new third stage instead of the orbiter, but...

As I wrote, it's probably a dumb question, but intriguing.

Because we simply cannot build any more Saturn Vs. We have assorted blueprints lying around, but none of the tooling or manufacturing infrastructure for building them survives. So building new Saturn V rockets would require starting from scratch, whereas the new Ares rocket will supposedly reuse existing preexisting SRB manufacturing infrastructure.

[Count Chocula]

Building on what Terwyn said, not only are the tooling and infrastructure gone, the scientists and engineers who designed and built the Saturn V are retired or dead. It was built by Boeing, North American, and Douglas. Of the three, only Boeing survives as a company (having acquired the "Douglas" part of MacD).

The brains and experience to resurrect the Saturn V just ain't there. It makes more sense all around to develop a new booster, that the new crop of rocket scientists will know inside and out for the next 30+ years.

The STS itself is also being phased out of service, with a much-reduced flight schedule past 2010. The phaseout, of course, is contingent on the Ares I launch vehicle and Orion crew module being ready in 2014.

Shuttle Endeavor, by the way, launches this Friday around 8PM from Kennedy, carrying an extra bedroom to the ISS.

Bile-producing trivia bit: the Orion program logo was designed by Mike Okuda!

[Darth Wong]

People don't realize how difficult it is to reuse old engineering; in practice, it is often easier to just start fresh. By the time you get done tracking down old drawings, trying to acquire or fabricate replacements for the obsolete equipment referenced in the bills of material, refurbishing old tooling or fabricating entirely new tooling, designing new components where necessary to fill in holes in the records, develop assembly procedures, etc., there are going to be real questions about whether you've saved any time or money, or whether you've in fact burned a whole lot of it for no gain at all.

Same goes for the idea of making "minor modifications" to a complex system. A minor modification to the requirements for a complex system is not necessarily a minor modification to the system.

[Samuel]

People don't realize how difficult it is to reuse old engineering; in practice, it is often easier to just start fresh. By the time you get done tracking down old drawings, trying to acquire or fabricate replacements for the obsolete equipment referenced in the bills of material, refurbishing old tooling or fabricating entirely new tooling, designing new components where necessary to fill in holes in the records, develop assembly procedures, etc., there are going to be real questions about whether you've saved any time or money, or whether you've in fact burned a whole lot of it for no gain at all.

Same goes for the idea of making "minor modifications" to a complex system. A minor modification to the requirements for a complex system is not necessarily a minor modification to the system.

How much easier is this due to current tech? I know the computers are lighter now , but are any other parts better than they were in the 1970s?

[NecronLord]

For the record, I wasn't proposing actually building a literally 'slightly updated' Saturn V. But for using multi-stage rockets to launch lunar missions, in the same style (as with the proposed Ares rockets), rather than some kind of direct re-use of shuttle components with a different manned vehicle on it.

[PeZook]

The board decided to not let me post this earlier for some reason:

You mean, why not just bolt a lunar third stage onto the ET and SRBs? For a start, I expect that the ET is configured for a fairly specific distribution of mass on the orbiter. Which is just fine for a re-usable 'space truck' design that's standardised. A lunar rocket, on the other hand, could be called upon to transport a number of different missions, depending on the intended permanance of a prescence.

What's more, your lunar vehicle would then have to do the work of a second stage, running off the shuttle ET, which means you've got to sacrifice some space on the orbiter to house engines that run off the (jetissoned) ET. Or put a rocket engine on the ET... at which point you're basically designing a new vehicle anyway, so why not go with what's known to work for this mission, and build a bigger, better, updated Saturn 5?

I actually suspected the mass argument: a lunar ship would be a completely different beast, and since the shuttle is steered mostly by thrust vectoring during ascent, this means mass distribution is probably a biggie.

And guys, I know NASA can't simply rebuild the Saturn V. That's not what I was asking about

(Hell, I made a passtime out of berating idiots who go "If NASA went to the moon 60 years ago why can't they do it now, huh? Just build another Saturn! FRAUD!!!)

I'm not able to find any detailed information offhand on the deltaV of the shuttle's disposable components. But I would seriously consider that the whole apparatus might not be able to provide equivalent deltaV to the Saturn V's first two stages, too.

It lofts about 112 tonnes to orbit (shuttle+payload in the cargo bay), which is 6-8 tonnes less than the Saturn, but the whole STS assembly also masses 1/3 less. The Shuttle is a pretty impressive vehicle, to be honest, if quite expensive to use.

[NecronLord]

It lofts about 112 tonnes to orbit (shuttle+payload in the cargo bay), which is 6-8 tonnes less than the Saturn, but the whole STS assembly also masses 1/3 less. The Shuttle is a pretty impressive vehicle, to be honest, if quite expensive to use.

Indeed. The proposed Ares models use a lot of the best features of shuttle technology. Particularly its solid booster first stage.

[Singular Intellect]

Is there a reason why we haven't spent more time and funding on devoloping atmospheric launchers to get our spacecraft into orbit? Like shuttles hitching a ride on 747 sized aircraft with high end top speeds before doing a burn to get into orbit?

[PeZook]

Is there a reason why we haven't spent more time and funding on devoloping atmospheric launchers to get our spacecraft into orbit? Like shuttles hitching a ride on 747 sized aircraft with high end top speeds before doing a burn to get into orbit?

You need way higher speed and altitude than what a 747 is capable of for this to be meaningful. It's actually a great idea, just needs a lot of improved tech to work. Rockets are cheaper so far.

[Singular Intellect]

Is there a reason why we haven't spent more time and funding on devoloping atmospheric launchers to get our spacecraft into orbit? Like shuttles hitching a ride on 747 sized aircraft with high end top speeds before doing a burn to get into orbit?

You need way higher speed and altitude than what a 747 is capable of for this to be meaningful.

I knew that much. My reference to a 747 sized aircraft was merely a nod that I doubt such a system is going to work with something the size of your average bi plane.

It's actually a great idea, just needs a lot of improved tech to work. Rockets are cheaper so far.

Ah, so the issue is still cost and refinement of technology.

[GrandMasterTerwynn]

Is there a reason why we haven't spent more time and funding on devoloping atmospheric launchers to get our spacecraft into orbit? Like shuttles hitching a ride on 747 sized aircraft with high end top speeds before doing a burn to get into orbit?

Piggybacking is fine if you're talking about small vehicles (such as small satellites atop rockets, or a manned vessel which is only making a sub-orbital hop,) and you're willing to wait a while as the mothership makes the climb to altitude. For anything that hopes to go much larger and much higher than SpaceShipOne, you will need a rocket, or some other means of providing the energy required to reach LEO.

[Broomstick]

How much easier is this due to current tech? I know the computers are lighter now , but are any other parts better than they were in the 1970s?

I would expect there have been significant advances in metals and composites as well, just for starters.

[The Big I]

When congress passed the bill to give NASA the cash to build the shuttles. It was on the proviso that all the Saturn V rocket blueprints were destroyed.

[Darth Wong]

How much easier is this due to current tech? I know the computers are lighter now , but are any other parts better than they were in the 1970s?

I would expect there have been significant advances in metals and composites as well, just for starters.

Not to mention the ability to analyze structures built of those materials using sophisticated FEA computer software, so they can optimize structures for weight and strength more effectively. And the ability to design complex 3D modeled shapes that would have been extremely difficult to design and fabricate using dimensioned line drawings on paper.

[Singular Intellect]

When congress passed the bill to give NASA the cash to build the shuttles. It was on the proviso that all the Saturn V rocket blueprints were destroyed.

And what kind of fucking dumbasses thought that up?

"You know that proven and working technology we have designs for? Destroy all it's blue prints...then we'll give you the funds to invest in a new idea!"

[PeZook]

The blueprints weren't "destroyed", they're stored on microfilm. It's just really hard to build an actual Saturn V with them - see Mike's post.

[Sea Skimmer]

Is there a reason why we haven't spent more time and funding on devoloping atmospheric launchers to get our spacecraft into orbit? Like shuttles hitching a ride on 747 sized aircraft with high end top speeds before doing a burn to get into orbit?

The Pegasus air launched booster has been used about 40 times so far, 825lb payload to LEO, dropped from a B-52 for early flights and now an L-1101. That’s the kind of role air launch can actually save money on, things which are already small and low cost. Minor costs savings can potentially open up a lot more market. Meanwhile of you save say 20 million out of a 300 million dollar launch cost… well that’s not going to gain you much extra business.

A subsonic aircraft provides maybe 4% of the velocity and even less of the altitude a rocket needs to reach orbit. This is a significant saving, but it still means if you want to put a big payload in orbit you still need a very large and very heavy rocket. The higher the orbit you want, the less the advantage air launch is, and most satellites want to go much higher then LEO. A 474 can only barely transport the space shuttle with no payload, and no internal fuel, never mind the weight of the external fuel tank. If you want to LEO a payload of more then a 5-6 tons then the weight of the rocket will easily exceed the 250 ton payload of even the An-225. An An-124 launched concept was considered, it would have put 4 tons in LEO. However using existing transport planes creates serious problumes with separation. An An-124 or 225 has to transport the payload on the roof, which is not good for ensuring the rocket actually detaches. Pegasus is small enough to be dropped from under a wing, hugely simplifying things.

The Soviets actually designed a couple transport planes (on paper only of course, and with the ability to suspend massive weights under the airframe) with eight and even ten engines specifically to try to increase the weights they could air launch, but even those wouldn’t have been able to carry a rocket all that potent. System 49-M was one such example, with eight engines it would have weighed 770 tons (all my tons in this post are metric BTW) on takeoff with a small spaceplane + giant fuel tank for spaceplane as 200 tons of that. This would lift 9 tons to LEO. The cost of a whole new mega plane and a whole new rocket were considered far too much for even Soviet excesses, and they poltically perfered a direct reply to the American shuttle anyway.

As an alterative to huge planes, one can seek out supersonic planes instead. For a time the Russians tired push a booster air launched from the mach 2.3 capable Tu-160, but no one was interested. Previously they considered dedicated designs reaching past mach 4, but since a supersonic plane of that speed could have only a limited payload (the drag of the rocket alone will already limit how much you can realistically expect to carry at those speeds) they could only make sense for military applications. The Spiral 50/50 air launched rocket bomber was one such concept.

All of these options work out to be highly expensive to design and test, and this is not sufficient to cover the slight reduction in the size of the expendable rocket. The reality is it’s a almost certainly a better idea to just build larger production runs of conventional boosters to drive down costs. The cost of space launches are plagued by very small production runs of each sort of rocket. As an alternative for those demanding better technology, one could also look into spending that same design and testing money on creating a conventional space booster which has an air augmented rocket stage. That way you save a lot of tonnage of oxidizer as you pass through the lower atmosphere. The ideas been around since the 1960s, but making it work is hugely expensive. However it’s now being applied to certain air to air missiles, so its possible this will help drive improve technology towards something practical for larger scale uses.

So yeah, until we have a 750 ton MTOW mach 4 transport… bests to stick with big dumb boosters fired off the ground.

[K. A. Pital]

Making boosters recoverable (Energia, STS) is also a great step forward from disposable ones. If they are capable of immense liftoff (100-200 tons to orbit), even better, each launch of such a rocket is sizeable enough to seriously impact one's orbital infrastructure.

[Count Chocula]

Building on what Stas said, from an economic standpoint it seems reasonable that sacrificing say, 8% of payload capacity to make the booster system - at least the first stage - re-usable would allow for more launches for a given annual budget. With modern composites and the experience of the STS, boosters should more easily survive launch and then water landing than the 1960s aluminum fuel silos we know and love.

I imagine that reconditioning the booster before reuse would take some time, but I don't have any direct experience. Is anyone aware of the decision-making process that was used for the development of the Shuttle's reusable solid rocket boosters?

[Beowulf]

It lofts about 112 tonnes to orbit (shuttle+payload in the cargo bay), which is 6-8 tonnes less than the Saturn, but the whole STS assembly also masses 1/3 less. The Shuttle is a pretty impressive vehicle, to be honest, if quite expensive to use.

Indeed. The proposed Ares models use a lot of the best features of shuttle technology. Particularly its solid booster first stage.

I thought the solid booster first stage was one of the worst features of shuttle technology. They're reusable in a sense, but require essentially complete refurbishment of the booster for reuse. It's almost as cheap to just build a new booster. It's responsible for half the failures of the STS. The way they're using the booster in Ares I essentially requires reengineering the fuel grain, which isn't cheap.

[Kanastrous]

Bile-producing trivia bit: the Orion program logo was designed by Mike Okuda!

mmph.

Looks like something of Mike's, all right.

Gotta hand it to him; the fellow's a genius at self-promotion.