DreamChaser partners with StratoLaunch

[Rune]

So, a non-related search through google led me here:

http://www.ai.mit.edu/projects/im/magnus/bh/analog.html

To summarize, it's a paper about Black Horse, a study by Zubrin (among others) circa 1993 about a SSTO rocket spaceplane using Aerial Propellant Transfer (APT) as the enabling technique. Without going into much detail (go to the paper! It's gold!), I'll just say here that looking at the assumptions (4% tankage weight, T/W 60 on the rocket engines at close to theoretical isp for each propellant combo), and the resulting (theoretical) feasibility of the concept, an idea sparked in my mind that I wanted to bounce off of you guys.

See, the main point of the study was to use an existing tanker to top off oxidizer at mach 0.8 and high altitude, therefore minimizing both drag and gravity losses (about 270m/s gained, so nothing to write home about) and, most importantly, minimizing the weight impact of runway-related gizmos like landing gear and wings, themselves largely dominated by takeoff weight loads. Turned out respectable payload fractions, and incidentally made a case for dense propellants, with JP5/H2O2 coming a close second to the much more efficient CH4/LOX combo under some assumptions, and H2/LOX shown as the low density mess it is, even without considering its deep cryogenic nature very extensively.

So with all that in mind, I suddenly thought about Stratolaunch's shiny new . That beast is supposed to loft a 485,000 lbs rocket, so why not a 485,000 lbs reusable spaceplane? The original Black Horse got 1mT out of ~200,000 lbs wet mass at separation form the tanker, so this should double the payload at least. I say at least because launching from a true carrier instead of doing a midair refuel allows a further decrease in mass of landing-related gizmos, and the carrier itself can supply propellant topoff until the last second, with no fuel used for ascent at all. I wouldn't develop it if I had to start from scratch, mind you, but Stratolaunch is already kind of committed to building this monster, and equipping it with cryogenic topoff capabilities too.

Engines options would be even better than in the original study (which baselined RL-10 derivatives for H2/LOX and CH4/LOX, NK-31's for hydrocarbon fuels). Now you could have either a single BE-4 Methlox 500,000 lbs class engine (not my ideal choice unless it has a very deep throttle capability), or SpaceX's awesome Merlin 1D with its huge T/W and a size suitable for a multi engined config (engine out capabilty), with throttle and reusability built in and already flying. And I know SpaceX turned down building a booster for Stratolaunch, but buying engines so Orbital or others can integrate them (they are geniuses at using other companies' hardware) shouldn't be so disruptive to their workflow, so a question of money I imagine. Blue's engine has the advantage of performance and availability (contractually obligated to offer in open market, IIRC), but a SSTO really likes more than one engine so it can deep-throttle by shutting some of them off, due to the huge weight change during flight. And of course however fundewd it is, it's still a paper engine.

The biggest hurdle, as always in reusable orbital designs, would be TPS weight fraction, but considering the propellant fraction, density at reentry should be low enough that a much gentler, higher gliding path could be set up, like Skylon, perhaps allowing all-metal reusable heatshields with at most carbon-carbon leading edges and a reasonably low weight. Remember, this should renter much more gently than the shuttle, with smaller wings if any.

All in all, while it won't come close to equal the payload of the expendable multistage system Orbital is building, such a system would have a more than respectable payload fraction (for a SSTO at least), much greater operational simplicity, stupendous reusability potential, and the wow factor is off the scale, which could be its main selling point, especially for manned flights after the airframes are certified unmanned in an aircraft-like test program with tens or hundreds of flights. Worth looking into, don't you think? Especially considering the hype about reusability SpaceX has sparked recently, and the growth potential of the concept hinted at on the paper, which also looks at airbreathing derivatives boosting to up to mach 5.5 on air after leaving the carrier.

Rune. I'd bet the Air Force and Darpa would be interested, they like futuristic concepts.

Edited October 6, 2014 by Rune

[Kryten]

http://www.seattletimes.com/business/boeing-aerospace/space-wa2/

Stratolaunch are no longer working with SNC or OrbitalATK, as the rocket wasn't 'hitting the economic sweet spot'. They're still building the plane, but it currently has no LV or payload.

[B787_300]

lol,

so they are pouring money into a plane that has no purpose?

[Kryten]

They're looking over their options for replacing the LV; I doubt they'll find one, at least a practical one.

But even if that does happen, it'll have served it's purpose admirably; it got 'Stratolaunch: a Paul Allen project' in the news for years. They don't call it 'Egolauncher' for nothing.

[sojourner]

They can always fit it with a cargo pod and rent it out as a massive transport craft.