7 thoughts on “Stratolaunch”

  1. Good summary. I agree, 7 tons to LEO, 2 tons to GEO, “about 1 commercial GEO satellite a year with a mass less than 2,500 kilograms projected for launch through 2020.” Not enough market. And competition from others. They’ll really need to kill them on price, and that will mean ALOT of volume, which I don’t think is there. This is key:

    It may turn out that Stratolaunch can beat out those other vehicles on price when it is introduced. (Company officials haven’t disclosed a target launch price for the vehicle.) However, given the inelastic nature of many of these existing markets, a lower-priced alternative may not stimulate much, if any, additional demand. This would force Stratolaunch to compete head-to-head with other companies (including potentially SpaceX) for the limited number of launch opportunities in this portion of the market.

  2. It seems to me that Stratolaunch could focus on being a mothership.
    Rather than unique service in regards to space payload. What they obviously would have is an unique service in terms of being that size of mothership.
    Instead of Galactic or Pegus being competiors, they could be a couple of their customers.
    Suppose galactic starts flying with ShipShipTwo, and that goes well, if Stratolaunch is available, instead Galactic focusing building their next generation mothership, they work on the rocket and use Stratolaunch in at least the testing phase. Pegus if there is an operational Stratolaunch could use larger rocket.
    So Stratolaunch could viewed a different type of airport/spaceport.
    But before this can be possible they need to launch rockets from the platform and prove it’s capabilities. One has the regulatory parties- and more so if involved with multiple parties but if this can be overcome, one become one of few providers of motherships.

  3. Since this craft will serve as a stage 0, I think it might be beneficial to compare it to other stage 0 concepts, in terms of size, scalability, and versatility.

    If I was going to throw a couple $billion at the problem, I might prefer to pursue a commercial jet engine/vertical take-off option.

    *** geek napkin doodle follows ***

    The Stratolaunch design delivers approximately 500,000 pounds to 30,000 feet and 300 knots.

    A GE90-115B weights 16,000 pounds, delivers 115,000 pounds of thrust at a specific fuel consumption of about 0.25 lbs fuel / lb force / hour.

    If the stage accelerates at a mild 1.2 G’s from launch, it should hit mach 0.7 at 38,000 feet in 110 seconds, consuming 900 pounds of fuel per engine. So let’s allow about 2000 pounds of fuel per engine (so it can, if need be, land with the payload still attached), and allow 2000 pounds for the tanks and engine mountings, giving us a weight of 20,000 pounds per engine. Each engine thus delivers 95,000 pounds net force, which means each engine can accerelate 80,000 pounds of mass at 1.2 G’s. Stratolauncher delivers 500,000 pounds mass, so it would take six of the GE90-115B’s to do similar service.

    *** end of geek napkin section ***

    The Stratolauncher’s engines are each about half the thrust of the GE90-115B, so by doubling the thrust you can eliminate the wing and fuselages. Certainly you get some limitations on range, but you gain a bit in altitude, launch velocity, and launch angle. The GE90 engines should cost about $30 million each, so six and a simple mounting structure should cost far less than the projections for the Stratolauncher.

    Most importantly, the system should scale up. You could redesign for 12 engines instead of six and double the payload vastly easier than the Stratolauncher can be scaled up, if it can even be scaled up, as it’s already bumping against size limitations both in span and available runways and hangers.

    1. I don’t see anything glaringly wrong there, and I would think you’d gain more than a “bit” in altitude, launch velocity, and launch angle. Has that (jet/vto) been done before?

      This was interesting from the wiki on GE90-115B

      According to the Guinness Book of Records, at 127,900 lbf (569 kN), it holds the record for the highest thrust (though it is rated at 115,300 lbf (513 kN)). This thrust record was accomplished inadvertently as part of a one-hour, triple-red-line engine stress test. In order to accommodate the increase in torsional stresses an entirely new steel alloy (GE1014) had to be created and then machined to extreme tolerances.

    2. Um, .25 lbs fuel/pound thrust/hour? Maybe I am Rip Van Winkle and haven’t read AvWeek in 20 years, but I thought that the low .5’s would be an achievement, given the laws of Thermodynamics. Have engines improved that much? I kind of doubt it.

      The other thing about jet engines of all kinds is that they are like the pokey un-altitude compensated un-turbo piston engine on your lower-end general-aviation craft. A professor at Caltech once explained this all to me — that the thrust rating diminishes with air density is how jet airplanes get such good cruise fuel economy because turbines notoriously are fuel hogs at reduced power otherwise.

      Those thrust ratings are thrust at sea level, and they de-rate something fierce up into the flight levels. You are not going to get anywhere near 115,000 pounds thrust at FL380.

  4. Ack, it ate my comment due to a cookie failure!

    Anyway, 0.25 lbsm/lbf/hr is about what the newer engines produce, due to a much higher compression ratio and bypass ratio.

    However, you’re definitely right about the decrease in thrust versus altitude. I totally forgot about that. *** Did I not say it was a napkin doodle?! ^_^ That part must’ve been obscured under a Guinness stain.

    I crunched more numbers, and the system is still quite workable but the required number of engines goes up. There might be a major benefit to using a large afterburning supersonic turbofan like the P&W F135, which produced 50,000 lbs of thrust at sea level and has a much better power to weight ratio, though a much, much lower SFC.

    Still, even up through Mach 2 these kinds of engine’s specific impulse won’t fall below 1,500, so it’s still much more efficient than a rocket and fully reusable. It would make an ideal design study for a NASA center, but unfortunatly it might somehow imply that the SLS isn’t the ideal solution.

  5. I think human spaceflight is all they’re interested in and the satellite talk is just talk.. just like it was at Virigin Galactic. They’re building this system for a new market.. if you build it they will come.

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