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.
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.
Quote from: Jim on 12/20/2011 04:57 pmActually, 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.
Quote from: Jim on 12/20/2011 04:57 pmQuote from: Zed_Noir on 12/20/2011 03:23 pmI 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.
Quote from: Zed_Noir on 12/20/2011 03:23 pmI 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 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.
If you assume that the airlaunch is not volume limited, but only GTOW limited.
Quote from: baldusi on 12/20/2011 05:40 pmIf 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.
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.
Not sure I'd call LOX-Propane storable.
Quote from: HMXHMX on 12/20/2011 07:48 pmNot 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.QuoteAlso, 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?
Quote from: Tcommon on 12/20/2011 03:37 pmQuote from: Zed_Noir on 12/20/2011 03:23 pmI 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 comparisona. Delta IV or Atlas V use it without major issuesb. The shuttle did not have "a lot" of leaksc. it did not cost "extra"
Quote from: Zed_Noir on 12/20/2011 03:23 pmI 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.
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...
Quote from: HMXHMX on 12/20/2011 07:48 pmAlso, 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 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.
Quote from: sanman on 12/20/2011 09:49 pmI 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