Envisioning the world of 2100

[publiusr]

Flawed logic. The first thing they tell you in systems analysis is that bad money is bad money and throwing good money after it won't change that fact.

Bad money is throwing away LV after LV to fill a leaky Depot. That's throwing away good money after bad. Price per pound of payload doesn't change that fact. All an HLLVs hydrogen gets instantly used. Price per pound isn't the only think to look out. Shroud diameter is another plus SLS has over Falcon.



Of course, the EELVS could, and for the most part they have. Mainly because they operate on a smaller scale, spreading experience and technical knowledge over a higher flight rate allows them to make developmental improvements a few at a time and evolve their capabilities into new technologies.

SLS uses D-IV as an insertion stage in that it is a payload for SLS and thus its reach becomes greater. Not either or--both/and

A man on Augustine who trashed HLVs, gave us the Roton.

A man on Augustine who supported HLVs is still beating his wife.

See, I can do that too.

Anyone who kept up with greason knows his Roton is a joke. Griffin wrote an AIAA textbook on spacecraft design.

[sojourner]

publiusr wrote:

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Griffin wrote an AIAA textbook on spacecraft design.

And yet still managed to run the Constellation program into the ground.

I'll say it again. a hugely overpriced HLV launch cannot compare to MLV's that cost a small fraction. Even with your version of depots being "leaky" and the added complications of assemble in orbit MLV's are still the best way to go. The price gap is just to large. SLS will cost billions to launch. How many F9's could you launch for the price? how much payload tonnage? Do the math. It doesn't lie.

I'll give you this. The one time a HLV has an advantage over multiple MLV's is when you have a payload that cannot be broken down into parts. Like a huge single mirror telescope. But you will pay out huge for that.

[gturner]

sojourner wrote:

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I'll give you this. The one time a HLV has an advantage over multiple MLV's is when you have a payload that cannot be broken down into parts. Like a huge single mirror telescope. But you will pay out huge for that.

Given that Hubble and Webb cost about $7 to $9 billion (inflation adjusted, etc), I don't think NASA would have the money for SLS and a very large single mirror telescope payload, especially given the long, drawn out lead times on the Webb.

However, if a large space telescope could give them a justification for building the SLS (like space stations did for the Shuttle) I'm sure they'll start the design studies.

Frankly, the MLV concepts would aproach a large space telescope program by asking how hard it would be to form the mirror in space, because if you can do that you can build telescopes vastly larger than any conceivable ground-launch could deliver.

From the perspective of settling other planets, the next big threshold is actually seeing nearby alien planets, or at least getting spectral data from them.

[sojourner]

You did see where I said "huge single mirror" right? Of course a multiple mirror telescope could be sent up on MLV's.

Frankly, NASA doesn't have the budget to build SLS and payloads to put on it.

[gturner]

sojourner wrote:

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You did see where I said "huge single mirror" right? Of course a multiple mirror telescope could be sent up on MLV's.

Frankly, NASA doesn't have the budget to build SLS and payloads to put on it.

Oh, I did see that, and I'm not suggesting multiple-mirror telescopes with conventional mirrors launched from Earth, I'm thinking of giant single mirror (or multi mirror) telescopes where you fabricate the mirror in space.

Regardless of whether your mirror is single or segmented, in space it can be extremely thin, light and structurally weak, barely more than a backing for a reflective layer, far beyond the point where it couldn't survive 1G, much less 3G's in and the high shock and vibration environment of a launch. The payoff in mirror area per pound would certainly be ten-fold, and probably be a hundred-fold or more as the techniques mature.

Getting there would take a lot of engineering and experimentation, much of it in orbit, perhaps exploring ways to make rigid aerogel substrates and vacuum coat them to provide a reflecting surface, then a way to smooth and polish the desposited surface to optical quality. If nothing else, it would be learning how to frit-bond very thin thin webs of pre-machined ULE glass to a lightweight face. We'd be pushing the bounds, figuring out what we can do, and then how to do it, with lots of failures and mis-steps along the way.

Does an aerogel (the world's most rigid substance by weight) make a good backing? How much vacuum deposition does it take to leave a polishable surface of glass, silica, or metal? How do you accurately form a parabola or hyperbola (especially the convex secondary) in free fall? Can you make an inflatable blanchard grinder? Do you have to? If you use frit-bonding or other methods of assembly, will you have to re-anneal the the assemblies?
Can you build mirrors in a Bigelow habitat, perhaps launching extremely thin, ?

Small, cheap launches, especially to a commercial space station like a Bigelow module, or even to the ISS, could make progress on such questions, whereas the SLS launches are so expensive that they'd only conceivably launch a fully assembled and tested space telescope with a mirror built on the ground in the conventional fashion, which means the mirror and its mounting have to survive high shock, vibration, and G loads. Even if they built it, we'd still be in the 10-meter class, and we'd only launch one, and the technology and techniques would never lead to something bigger, or cheaper. Basically, whatever space telescope the SLS launches will be a technological dead-end, because the future of space telescopes is making them huge, thin, and light.

[publiusr]

Atlast was going to be a single mirror. Webb shows that multiple mirror designs can be as complicated as a transformer toy

In terms of Greason

At least Greason has a bit of a sense of humor: http://www.airspacemag.com/space-exp...aunch-Lab.html

" I stammer for a word more diplomatic than 'failure' to describe Roton, which he worked on over a decade ago. 'Just go ahead and say it,' Greason laughs."

Oh well, all's well that ends well.

http://www.spacenews.com/civil/10090...nasa-bill.html

The Senate bill, he wrote, provides “nearly everything I could want to see for NASA at this point, given political reality,” despite its prescriptive nature, which calls for developing a heavy lift launch vehicle based on technologies derived from the space shuttle program and Constellation’s Ares rockets that Obama seeks to abandon.
Saying the Senate language puts NASA “in a box with respect to heavy lift,” he said the upshot is that NASA likely would develop a launch architecture for deep space missions similar to the space shuttle-derived DIRECT proposal briefed to the Augustine Committee last summer by a group of renegade engineers.
“My own opinion – I don’t expect all of you to share it – is that this is the right answer, and in fact this was my view a year ago,” Chyba wrote, adding “whatever misgivings one may have about the Senate bill

Good scope for heavy lift
http://arxiv.org/abs/1209.3199

More
www.spacelaunchreport.com/

[gturner]

So they spent over 30 years rejecting Shuttle-derived cargo versions, and now it's suddenly a good idea? Might be something about the jobs.

[Crazy Eddie]

publiusr wrote:

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Flawed logic. The first thing they tell you in systems analysis is that bad money is bad money and throwing good money after it won't change that fact.

Bad money is throwing away LV after LV to fill a leaky Depot.

More flawed logic. It's only "bad money" if the depot itself is under-utilized and the amount lost to leakage hugely exceeds the amount lost to operations (in which case there's no point having a depot; you should launch the refueling tankers directly to the ships that need them). That would occur if you were using a depot to store cryogenic propellants for long periods of time, which is a silly idea and would be easily mitigated by switching to hypergolics.

Price per pound isn't the only think to look out. Shroud diameter is another plus SLS has over Falcon.

Thinking big is one thing, but don't forget to think LONG. At the time the Senate Launch System goes online, it will be the only launch vehicle in existence with an eight meter shroud. It will also be the most expensive launch vehicle in existence and will have the scarcest launch opportunities. At the same time, smaller rockets like Ariane V, Atlas V and Falcon 9(H) will have been flying for years or even decades with a 5.4 meter shroud, which means ten years worth of payloads will have adapted to that standard. Which means, in turn, that the most mature spacecraft designs will have always adapted to that standard. Actually, considering the number of spacecraft designs derived from the MPLM shell, that is already happening now. Even Orion is small enough to be launched on a medium lift vehicle, and I have a suspicion that it will be, more often than not.

That means that by the time the SLS goes online, there will be literally no one in the entire world who needs an 8 meter payload shroud. The only people who will EVER use the SLS is NASA, who -- if and when they ever develop a service module for Orion -- ALSO won't need an eight meter shroud diameter, because in the whole of NASA's history they have never designed a spacecraft that required one, and in the unlikely event they ever DO, your HLV will be retired by the time they get around to building it.

SLS uses D-IV as an insertion stage...

An insertion stage for WHAT? They still haven't figured out what they're going to USE this thing for.

Griffin wrote an AIAA textbook on spacecraft design.

Is he still beating his wife?

[Crazy Eddie]

gturner wrote:

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So they spent over 30 years rejecting Shuttle-derived cargo versions, and now it's suddenly a good idea? Might be something about the jobs.

Bingo.

And FYI, they ultimately DID reject the shuttle-derived cargo version, since they decided to

- Redesign the SRBs
- Redesign the main engines
- Redesign the ET to allow for an inline configuration
- Totally abandoned any discussion whatsoever of the sidemount configuration

The singular advantage of the DIRECT program was that they didn't have to DEVELOP anything at all; the side-mount configuration wasn't even a significant modification to the STS, it was really just a MODIFICATION of the existing stack by omitting the only truly expensive component of the system itself. The result is that a relatively practical spinoff of the shuttle program turns into a totally new design that is only distantly related to the shuttle at all.

[gturner]

But the new SRB's and engines are expendable!

They figured out how to expend them. Probably at increased cost...

Strangely, at the SLS's lower flight rate, Thiokol and Rocketdyne might not even have to increase their production rate of building brand new engines.

Early in the development of the Shuttle they considered putting the SSME's under the external tank (the aeronatical engineers were saying it was very advantageous, especially early in the flight, since the thrust vectors would be more aligned with the center of mass). But they still wanted to re-use the expensive engines, so they explained that after main engine shutdown the engines needed to somehow swing over from the ET to the back end of the shuttle, allowing it to jettison only the ET. The mechanical engineers started screaming about how hard that would be, a design nightmare that would probably weigh a lot, never work well, and where any failure (engines stuck halfway) would definitely result in the loss of vehicle and crew.

And that was the end of that.

It seems to me a more sensible option would've been to mount the engines on their own re-entry capsule (heatshield forward like a firewall) and have the engines re-enter shortly after ET seperation, probably after a partial orbit so they could be fished out of the Pacific near Rocketdyne's plant.

That would create advantages with turn-around time, because while the Shuttle is in orbit for a week or two, the engines are already being refurbished in California, while a prior set of refurbished engines is being mated to an ET for the next launch. It seperates engine inspection and replacement from the Shuttle post-flight refurbishment cycle. It also saves all the cross-plumbing to the Shuttle, and also cleans up its entire back end, lowering the drag significantly, while saving significant orbital and re-entry weight. That would lower the required wing area and boost cross-range, or lower landing speeds. It also seperates the design of the orbiter component from the design of the first stage booster, allowing each to evolve or upgrade seperately. And of course it means that a main engine failure wouldn't rip through the back end of the Shuttle directly.

[sojourner]

gturner wrote:

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But the new SRB's and engines are expendable!

They figured out how to expend them. Probably at increased cost...

Strangely, at the SLS's lower flight rate, Thiokol and Rocketdyne might not even have to increase their production rate of building brand new engines.

Early in the development of the Shuttle they considered putting the SSME's under the external tank (the aeronatical engineers were saying it was very advantageous, especially early in the flight, since the thrust vectors would be more aligned with the center of mass). But they still wanted to re-use the expensive engines, so they explained that after main engine shutdown the engines needed to somehow swing over from the ET to the back end of the shuttle, allowing it to jettison only the ET. The mechanical engineers started screaming about how hard that would be, a design nightmare that would probably weigh a lot, never work well, and where any failure (engines stuck halfway) would definitely result in the loss of vehicle and crew.

Now, I've read a lot about the shuttles development over the years and never heard of anything like this. Either A) There was one lone idiot that came up with the idea and he was quickly shouted down, or B) This story is bullshit. Either way, I gotta ask, source?

It seems to me a more sensible option would've been to mount the engines on their own re-entry capsule (heatshield forward like a firewall) and have the engines re-enter shortly after ET seperation, probably after a partial orbit so they could be fished out of the Pacific near Rocketdyne's plant.

Several versions of this have cropped up over the years. You're not the first to have the idea.

[gturner]

sojourner wrote:

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Now, I've read a lot about the shuttles development over the years and never heard of anything like this. Either A) There was one lone idiot that came up with the idea and he was quickly shouted down, or B) This story is bullshit. Either way, I gotta ask, source?

It wasn't mentioned in the detailed book on the development of the Space Shuttle that I have, either, but was related by one of the project managers or Shuttle program directors in this:

http://ocw.mit.edu/courses/aeronauti...ing-fall-2005/

That's MIT's graduate level course in aeronautical systems engineering from the year they devoted the entire course to the Space Shuttle. The video lectures are free online!

For a geek, it was more fun than watching sci-fi shows, and I highly recommend it. There's lots of personal anecdotes, as each week features a guest lecturer who led part of the design teams (structures, aerodynamics, propulsion, navigation, etc) about how they designed it, and what they did wrong, and what they'd do differently.

The "move the engines over" idea was indeed just brought up in an early brainstorming session and never got to the level of a paper sketch. How would you even sketch that without wadding up the paper and throwing it in the wastebasket?

Anyway, lots of speakers and stories, and lots of design insights. I can't recommend it highly enough. The audio levels at the start of the first lecture are a bit low, but that gets fixed pretty quickly, and the student's projects were to pick a system on the Shuttle and design a better alternative, or make a significant improvement.

Among the other tidbits I learned:

Aluminum versus titanium for the structure was a complete toss up. The weight comes out the same (titanium weighs more but uses thinner tiles). So the program director said he flew out to talk to Kelly Johnson at Lockheed, who'd designed the SR-71 out of titanium. Kelly told him "Do not use titanium if you can possibly avoid it. It's a machining nightmare." So the shuttle is aluminum.

The engine hydraulics and flight control surfaces, if redone, should be driven electrically from added fuel-cells instead of with the APU's, which is vastly simpler and more reliable.

The main landing gear should've used four-wheel bogies instead of two-wheel, but the realization came too late because they'd have had to redesign the wing's landing-gear bays, and redesigns cost a lot of time and money (especially when they were done by guys sitting at drafting tables).

And of course it discuses the whole Air Force cross-range fiasco, along with how they botched the operation cost-estimates and flight-rate so badly.

[sojourner]

Sounds like something Publiusr needs to view.

[gturner]

Crap. I just realized how to make the engines pivot to the ET.

Taper the back end of the shuttle, a bit like it was a C-130. The engines are mounted to the cargo door (aiming backwards when the C-130 door is hanging way down like a ramp). Their fuel connetors go through the bottom of the door, not back into the Shuttle.

During mating (stacking), the door is "lowered" so it's back against the external tank, and the fuel connections are mated. It also pushes directly against studs on the ET to more directly transfer loads during ascent. The upper side of the Shuttle, above the door, is a more tapered version of what was used, and still houses the OMS pods, which don't pivot.

After main engine shutdown, the fuel connections seperate (as was done successfully on every Shuttle mission) and the aft engine door closes, mating seamlessly with the OMS pod to make a much more streamlined back-end to the Shuttle. (Note that when closed, the engines are actually aiming diagonally up and back). During descent and re-entry, the engine door is also the rear body flap.

That would take two bearings and one or two hydraulic cyclinders or screw jacks which are required for the main body flap anyway. It eliminates the horrendously complicated plumping in the back-end of the shuttle, because each engine could make its own direct connection to the ET. It lowers the mass (plumbing is simplified), improves ascent efficiency, transfer loads to the ET more directly, and greatly reduces the drag ratio for re-entry and landing.

The downside, which they probably would've missed, is that any foam coming off the ET would've slammed into the bottom of the opened engine door.

[Crazy Eddie]

gturner wrote:

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Early in the development of the Shuttle they considered putting the SSME's under the external tank (the aeronatical engineers were saying it was very advantageous, especially early in the flight, since the thrust vectors would be more aligned with the center of mass). But they still wanted to re-use the expensive engines, so they explained that after main engine shutdown the engines needed to somehow swing over from the ET to the back end of the shuttle, allowing it to jettison only the ET. The mechanical engineers started screaming about how hard that would be, a design nightmare that would probably weigh a lot, never work well, and where any failure (engines stuck halfway) would definitely result in the loss of vehicle and crew.

I've been told that the KGB acquired a number of these design studies when their space program was developing the Energia rocket for Buran. Since they ultimately selected liquid-fueled rockets instead of solid fuel for the stack, putting the engines beneath the main tank made a bit of sense, and ironically that means the Energia stack was more viable as an HLV than Buran was as a shuttle. I really do believe STS would have had the same evolvable potential if they had taken any serious efforts to "phase in" a cargo-carrying variant: first, by keeping the stack as-is and putting the engines in a recoverable pod at the back of the cargo barge, and maybe later moving the engine pod to the bottom of the external tank to be jettisoned later.

There's one thing that occurs to me to mention at this point, an it's this: It's not that I believe that heavy lift vehicles don't have any place in the future of space exploration (the Falcon Heavy is almost that already). Actually, I'm coming around to the opinion that NASA has no place in the future of space exploration. Even when they have access to the best engineering expertise on the planet, they are politically and systematically prevented from ever doing anything that makes sense.