Author Topic: Stratolaunch: General Company and Development Updates and Discussions  (Read 1020790 times)

Offline kevin-rf

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For some launches, F5 from the ground might be capable enough.  The ground infrastructure for F5 is almost the same as for F9 (2-level strongback needed).  I assume F5 would have the same thrust structure and mostly common plumbing with F9. 
A Ground launched Falcon 5 would require different nozzles, and will be shorter than an F9, so the second stage hookups will be different. Though that may be as simple as a dedicated "F5" strongback.
« Last Edit: 12/20/2011 05:21 pm by kevin-rf »
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Offline mmeijeri

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Actually, it is the opposite.  LH2 is more suited for airlaunch and provides more benefits since it is less dense and therefore the vehicle weighs less.

Mixed bag I think. Low density is bad, not good, it's the high Isp that makes LH2 interesting, not its low density. Boil-off is also very inconvenient. Some have even advocated the use of hypergolics for air-launch, because of high density and lack of boil-off, despite the handling difficulties and lower Isp. Conservation of inconvenience I guess, you can move it around but you can't eliminate it.
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Offline baldusi

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Actually, it is the opposite.  LH2 is more suited for airlaunch and provides more benefits since it is less dense and therefore the vehicle weighs less.

Mixed bag I think. Low density is bad, not good, it's the high Isp that makes LH2 interesting, not its low density. Boil-off is also very inconvenient. Some have even advocated the use of hypergolics for air-launch, because of high density and lack of boil-off, despite the handling difficulties and lower Isp. Conservation of inconvenience I guess, you can move it around but you can't eliminate it.
It's a matter of optimization. If you assume that the airlaunch is not volume limited, but only GTOW limited. And you take into consideration that the (normally) low T/W of H2 stacks gets particularly high benefits from airlaunch. Then the maximum payload for a given GTOW will be achieved with an H2 rocket. Boil off can be mitigated with better insulation, and some fill up pumping on the flight.

Offline Robotbeat

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One benefit of airlaunch is the low aerodynamic drag once at altitude. This can greatly diminish hydrolox's drag penalty. The drag experienced near sea level occurs when under turbofan power so isn't expensive.

(This is in addition to the maximizing of the payload to orbit for a given carrier airplane because of the much higher Isp.)

The boiloff issue can be mitigated with really good MLI (see Jon Goff's latest post on it: http://selenianboondocks.com/2011/11/tooting-someone-elses-horn-quest-product-development-corps-advanced-mli-technologies/ ) or in-flight fueling of the rocket.


I doubt anyone will consider using LH2 on an air-launched LV core stage anytime soon. The main issue with LH2 is it's a low density cryogenic fuel resulting in a bigger tank and vehicle as compared to a similar kerolox design.


Actually, it is the opposite.  LH2 is more suited for airlaunch and provides more benefits since it is less dense and therefore the vehicle weighs less.

Jim is right, for an air-launched vehicle there's got to be a pretty strong argument AGAINST LH2 not to use it.

The biggest argument is that there isn't a very cheap hydrolox rocket that could be adapted relatively easily for this. SpaceX's vertically integrated nature means they're pretty good at developing a new rocket and manufacturing for cheap... (SpaceX's weakness is operations, which is being taken care of by Stratolaunch and their partners.) They're already used to manufacturing dozens of the rocket engines and several rocket bodies in a relatively short period of time (now if only they could launch them...).
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Offline mmeijeri

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If you assume that the airlaunch is not volume limited, but only GTOW limited.

Ah, but do we know that assumption is true? The AirLaunch people advocated storable propellants, because of boil-off, drag (?) and volume constraints associated with LH2 / cryogens in general.
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Offline RocketmanUS

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Does the mother ship make LOX inflight from the air to replace what is lost in the rocket stages do to boil off?

Offline baldusi

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If you assume that the airlaunch is not volume limited, but only GTOW limited.

Ah, but do we know that assumption is true? The AirLaunch people advocated storable propellants, because of boil-off, drag (?) and volume constraints associated with LH2 / cryogens in general.
Airlaunch proposed to increase the height of wheels of a stock 747. They where volume limited, too. The Stratolauncher isn't. In fact, they show it with a full 5.2m fairing. So it would not be an issue. Plust, the double bodies have lots of internal space. Airlaunch and Stratolauncher are very different vehicles. Even different payload sizes.

Offline HMXHMX

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If you assume that the airlaunch is not volume limited, but only GTOW limited.

Ah, but do we know that assumption is true? The AirLaunch people advocated storable propellants, because of boil-off, drag (?) and volume constraints associated with LH2 / cryogens in general.

Not sure I'd call LOX-Propane storable.  The reason it was chosen against the clearly superior (for air-launching) LOX-LH2 combination was partly volumetric, i.e., fitting inside the C-17 and partly operational i.e., the USAF didn't want to deal with LH2 in a combat situation.  Once we had that stage developed, there was no reason to do it all over again with LH2 for external carry on the 747 (for the t/Space 2006 NASA proposal).

Also, for those who think LH2 is hard to handle, I'd point out that the semiconductor industry uses a significant quantity each day, delivered by truck, and handled by folks who don't have PhDs.

Offline Tcommon

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Also, for those who think LH2 is hard to handle, I'd point out that the semiconductor industry uses a significant quantity each day, delivered by truck, and handled by folks who don't have PhDs.
LH2 is harder and more expensive to handle than RP1 - but carry on, I'm enjoying this conversation immensely.

Offline Rocket Science

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In the vein of fuel safety and handling conversation,  if we were to reset the clock for motor vehicles and their use of gasoline and dispensing at filling stations. Throw in the context of government regulations, liability and a litigious society; we never might have had gasoline powered automobiles in modern times. One only needs to compare ordinary common gasoline vapor to the explosive equivalent of TNT.
In other words if someone came up with the idea of gasoline powered cars today, they would be called nuts…
« Last Edit: 12/20/2011 08:08 pm by Rocket Science »
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Offline mmeijeri

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Not sure I'd call LOX-Propane storable.

I think I recall a paper by Sarigul Klijn advocating hypergolics, but I couldn't quickly find it just now.

Quote
Also, for those who think LH2 is hard to handle, I'd point out that the semiconductor industry uses a significant quantity each day, delivered by truck, and handled by folks who don't have PhDs.

On the other hand, I remember evacuating a research lab because there was a leaking LH2 truck next to it. Not that I'd preferred hypergolics or anything...
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Offline MP99

Not sure I'd call LOX-Propane storable.

I think I recall a paper by Sarigul Klijn advocating hypergolics, but I couldn't quickly find it just now.
Quote

Also, for those who think LH2 is hard to handle, I'd point out that the semiconductor industry uses a significant quantity each day, delivered by truck, and handled by folks who don't have PhDs.

On the other hand, I remember evacuating a research lab because there was a leaking LH2 truck next to it. Not that I'd preferred hypergolics or anything...

I think you'd evacuate for a leaking hypergolic truck, too?

Cheers, Martin

Offline mmeijeri

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I think you'd evacuate for a leaking hypergolic truck, too?

You bet I'd try, but it might be too late by the time you noticed.
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Offline muomega0

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I doubt anyone will consider using LH2 on an air-launched LV core stage anytime soon. The main issue with LH2 is it's a low density cryogenic fuel resulting in a bigger tank and vehicle as compared to a similar kerolox design.

It's also difficult to work with - the Shuttle had lots of delays due to hydrogen leaks for a program costing $200 million per month. I think the extra cost of using LH2 was around $1 billion based on that.

Wrong, not a valid comparison
a.  Delta IV or Atlas V use it without major issues
b.  The shuttle did not have "a lot" of leaks
c.  it did not cost "extra"

LH2 Consumption During Space Station Program  was 54M lbs (24.5M kg)  times $5/kg =  $122M over its lifetime. 

Further, 29.6M On board quantity vs 54M purchased, so heat leaks and leaks accounted for 46% of the total.  Do you mean leaks or heat leaks (heat loss)?

So you seem to be stating that it took $200M/month labor to maintain the *leaks* and handling of LH2, yes or no?  Seems rather high ::)

Can anyone give the rate of replenishment of the External tank once it enters stable replenish (is this T-3 hrs?).

Offline MP99

It's a hard and fast rule of NASASpaceflight.com's forum: As soon as some hardware development is announced, users will immediately ask how to make it bigger...

So very, very true.

Cheers, Martin
« Last Edit: 12/20/2011 08:54 pm by MP99 »

Offline jongoff

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I doubt anyone will consider using LH2 on an air-launched LV core stage anytime soon. The main issue with LH2 is it's a low density cryogenic fuel resulting in a bigger tank and vehicle as compared to a similar kerolox design.


Actually, it is the opposite.  LH2 is more suited for airlaunch and provides more benefits since it is less dense and therefore the vehicle weighs less.

I'm with Jim.  LH2 has more challenging insulation requirements for air launch, but technology is catching-up with the challenges (see my insulation article on selenian boondocks).  And for air launch you have a hard GTOW restriction, and you're at a point in the trajectory where most of the gravity/drag losses have been taken care of (if you do your flight path angle right), so most of the disadvantages of LH2 go away.

~Jon

Offline sanman

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I know it sounds silly, but could this Stratolaunch approach be used for military purposes? Hey, people have tried sillier things.

Remember the MX missile and the idea of circulating it around on a railroad car?

Well, could you have Stratolaunch planes each carrying an ICBM around, like Cold War alert bombers? Here the plane wouldn't have to contend with penetrating enemy airspace like the bomber does, because it's just launching the missile. At the same time, it's mobile and more elusive than a fixed silo or ground-based launcher. It's not as well-hidden as a ballistic submarine, but it's more mobile than one.

If you were a 3rd world country, Stratolaunch could become part of a cheap deterrent system.
« Last Edit: 12/20/2011 09:50 pm by sanman »

Offline jongoff

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Also, for those who think LH2 is hard to handle, I'd point out that the semiconductor industry uses a significant quantity each day, delivered by truck, and handled by folks who don't have PhDs.
LH2 is harder and more expensive to handle than RP1 - but carry on, I'm enjoying this conversation immensely.

I think Gary's point was that unless you're dumber than the average Praxair delivery guy, LH2 is not a showstopper.  Just another consideration to be factored into the performance/cost/operability trades.

I can think of several things in Kero's favor (ready availability at an airport if your engine can handle the lower-quality aviation kerosenes being the single biggest one).  But what wins out depends a lot on what you're trying to achieve.  I think the anti-LH2 bent that a lot of people have in New Space is somewhat amusing.  To be fair I've never used anything much worse than LOX myself (though I have many friends who have LH2 experience and few of them think it's the devil-juice that some make it out to be).

~Jon

Offline Jim

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I know it sounds silly, but could this Stratolaunch approach be used for military purposes? Hey, people have tried sillier things.

Remember the MX missile and the idea of circulating it around on a railroad car?

Well, could you have Stratolaunch planes each carrying an ICBM around, like Cold War alert bombers? Here the plane wouldn't have to contend with penetrating enemy airspace like the bomber does, because it's just launching the missile. At the same time, it's mobile and more elusive than a fixed silo or ground-based launcher. It's not as well-hidden as a ballistic submarine, but it's more mobile than one.

If you were a 3rd world country, Stratolaunch could become part of a cheap deterrent system.


Huh?  wrong, that capability exists now, with current aircraft.  Stratolaunch isn't anything new.    The Stratolaunch aircraft is not going to be sold to just anyone.
« Last Edit: 12/20/2011 11:40 pm by Jim »

Offline Robotbeat

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I know it sounds silly, but could this Stratolaunch approach be used for military purposes? Hey, people have tried sillier things.

Remember the MX missile and the idea of circulating it around on a railroad car?

Well, could you have Stratolaunch planes each carrying an ICBM around, like Cold War alert bombers? Here the plane wouldn't have to contend with penetrating enemy airspace like the bomber does, because it's just launching the missile. At the same time, it's mobile and more elusive than a fixed silo or ground-based launcher. It's not as well-hidden as a ballistic submarine, but it's more mobile than one.

If you were a 3rd world country, Stratolaunch could become part of a cheap deterrent system.


Huh?  That capability exists now.  Stratolaunch doesn't change anything
Stratolaunch isn't going to be cheap. Missiles on a mobile launcher would be a lot cheaper and probably stealthier (can hide in caves).
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

 

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