Where does the engine come from? Energomash and Krunichev are now politically impossible, Yuzmash is far too risky, and AR haven't developed a new large hypergolic engine since the 60s (AFAIK).
Quote from: DaveJes1979 on 06/23/2015 05:52 pmAlthough there is a isp performance penalty vs. crogenic fuels, it might be desirable to have storable liquid propellants. They are dense, don't have the hazards of, say, hydrogen, and most importantly it would eliminate fuel transfer between the mothership and rocket, simplifying operations. Where does the engine come from? Energomash and Krunichev are now politically impossible, Yuzmash is far too risky, and AR haven't developed a new large hypergolic engine since the 60s (AFAIK).
Although there is a isp performance penalty vs. crogenic fuels, it might be desirable to have storable liquid propellants. They are dense, don't have the hazards of, say, hydrogen, and most importantly it would eliminate fuel transfer between the mothership and rocket, simplifying operations.
Or the Indian L40H Vikas 2 gas generator hypergolic engine rated at 150000 lbs (680 kN) of thrust with ISPsl of 262 sec.
Quote from: Zed_Noir on 06/23/2015 08:55 pmOr the Indian L40H Vikas 2 gas generator hypergolic engine rated at 150000 lbs (680 kN) of thrust with ISPsl of 262 sec.I would be shocked if Stratolaunch were considering hypergolic lower stages. The operational and bureaucratic hassles would be very large.
Well, looks like they've got an airplane to nowhere. At least for now.If I were looking into a rocket for air launch, Stratolaunch should consider walking across the street and knocking on XCor's door. At the very least to inquire about their piston rocket pumps. It might even be worth trading against electric battery pumps. Forget about solids, you end up with too many stages and separation events (keep it down to 2). And solids just aren't very safe if you will eventually put people at the front of the rocket.Although there is a isp performance penalty vs. crogenic fuels, it might be desirable to have storable liquid propellants. They are dense, don't have the hazards of, say, hydrogen, and most importantly it would eliminate fuel transfer between the mothership and rocket, simplifying operations. Since they are not at cryogenic temperatures, you might even be able to make your structure completely composite, excepting an inner liner in the tanks. N2O4/MMH is nasty stuff on the ground operations side, but is a pretty good performer. This is low TRL, but worth looking into if one insists on non-toxic storable propellants: https://catalog.data.gov/dataset/low-cost-high-performance-non-toxic-self-pressurizing-storable-liquid-bi-propellant-pressuIt would be good to retain the Pegasus-style carbon composite wing for the initial launch and pull-up (saves about 1000 m/s of delta V).
Quote from: Kryten on 06/23/2015 07:56 pm Where does the engine come from? Energomash and Krunichev are now politically impossible, Yuzmash is far too risky, and AR haven't developed a new large hypergolic engine since the 60s (AFAIK).For an engine try Masten Space Systems or Exos Aerospace (nee Armadillo Aerospace). They can sell upper stage engines even if they lack experience with large engines.
New large hydrazine engines develop from Masten or Armadillo? Too toxic for small company.Quote from: A_M_Swallow on 06/24/2015 08:40 amQuote from: Kryten on 06/23/2015 07:56 pm Where does the engine come from? Energomash and Krunichev are now politically impossible, Yuzmash is far too risky, and AR haven't developed a new large hypergolic engine since the 60s (AFAIK).For an engine try Masten Space Systems or Exos Aerospace (nee Armadillo Aerospace). They can sell upper stage engines even if they lack experience with large engines.
Solids have high acceleration, high atmosphere drag and benefit from air launch about 1000m/s.Liquids accelerate slow and have tiny benefit from air launch.
Besides, how to choose non-toxic storable propellants? HNO3/Amine have low toxicity compares to NTO/MMH but have low isp similar to solids H2O2 or N2O have spontaneous explosion risk.
Quote from: Comga on 06/08/2015 10:18 pmI did suggest "Glomar Explorer" as a precedent. However, I have no idea what the military would be after with Stratolaunch. Of course we in the public had no idea that the Glomar Explorer was going after a Russian sub. Some posters have suggested that Paul Allen is a fool, which is both rude and absurd. Guys like that don't get careless with money, although they can take big risks. We can guess that either he had some reason to believe that it would work better than others believed, or that its application would tolerate that poorer performance. This could be an unannouced use for its secondary benefits, which include unmonitored launches, on-demand inclination and orbital phase matching, and possibly others. Considering that they've now burned through two rocket providers, doesn't that indicate that they clearly don't have some super secret justification for it? If it looks like a program wandering around in search of purpose, then maybe it is a program wandering around in search of a purpose.And I don't think Paul Allen is a fool. I think he came up with a big idea without having good market research and engineering evaluation first. That kind of stuff happens a lot in business, and sometimes it pays off, often it doesn't, but usually it is not this high profile. He's also got a lot of money, and when somebody like that tells a bunch of people to "make it happen" they either get caught up in the vision (lots of people have worked on hopeless space projects before, it's the nature of this field) or they calculate how many years they can draw salaries from the project before it gets canceled and decide if it's worth it.
I did suggest "Glomar Explorer" as a precedent. However, I have no idea what the military would be after with Stratolaunch. Of course we in the public had no idea that the Glomar Explorer was going after a Russian sub. Some posters have suggested that Paul Allen is a fool, which is both rude and absurd. Guys like that don't get careless with money, although they can take big risks. We can guess that either he had some reason to believe that it would work better than others believed, or that its application would tolerate that poorer performance. This could be an unannouced use for its secondary benefits, which include unmonitored launches, on-demand inclination and orbital phase matching, and possibly others.
Stratolaunch and Virgin Galactic appear to be moving in similar directions (liquid LVs dropped from 747-derived carriers). Will they be competitors or partners?
Has there ever been a successful liquid air launch system? Seems to me after dropping the rocket, it would take a long time to start and throttle up. Compared to a solid.
