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Dreamchaser And Stratolaunch

22 Comments

I didn’t mention this earlier in the week, but SNC is teaming with StratoLaunch to get a subscale version into orbit. If it’s 75% scale, I figure that’s about 40% of the current interior volume, which lines up with their claim of being able to carry two or three passengers (the full-scale system is designed for seven). The big advantage of such a system would be single-orbit rendezvous, and runway landing, so if it happens, there’d certainly be a market niche for it.

22 thoughts on “Dreamchaser And Stratolaunch”

  1. Meanwhile, NASA is looking at deep sleep for a Mars mission because it cuts down the required mass and volume. I suppose it would also be handy because after the SLS launches the crew into Earth orbit, they’ll need another year or two to launch the SLS that will boost them on to Mars.

    1. Humph. The study looked at the effects on payload *if such a thing were possible*. Such a thing is *not* possible. No one has the first idea how to induce true torpor in humans. Clinical hypothermia and induced comas are not the same think at all, are only possible for hours or days at most, and require a standing army of ICU staff and a great deal of medical risk.

  2. I’m a fan of the Dream Chaser concept, but…. if we’re really talking a scaled down Dream Chaser, what that really entails is a totally new design. Basically, starting from scratch.

    For the above reason, the Stratolaunch option as outlined strikes me as vaporware. I hope I’m wrong.

  3. Would it really have to be totally new? How little would the lifting body have to be changed so that its structural material could still handle force and heat differences? Wouldn’t it not scale down the engines? They will have engineering costs of course but you’d think they’d have transferable knowledge from the full scale vehicle?

    1. If they are scaling down to 40% of the original size, then it’s a completely new vehicle. The square-cube law alone dictates redoing all the CFD.

    2. OTOH, there would be some transferable knowledge. The cockpit would have to be pretty much the same, the life support system and other subsystems have been refined by the company over many years and would likely stay largely the same.

      But they’re changing the size of the vehicle, so they’re changing the mass and center of mass and center of lift. The wings need to be a different size, and perhaps different angles as well. And it’s a lifting body, so they’ve basically got to redesign every contour. Then there’s the battery of tests, drop tests, and FAA-AST is involved. They’ve got plenty of work ahead of them.

  4. Why don’t they scale it up by 25% and turn it into a submarine? Methink it looks like a dolphin…
    I’m surprised how not everyone immediately see what a fraud this is.

    1. Why don’t they scale it up by a quarter and turn it into a submarine? Methink it looks like a dolphin.

  5. Hi Ken;

    The problem with scaling a spacecraft (or most any complex structure) up or down is that it’s not a matter of just reducing the size of every part by whatever percentage you need.

    One of the many, many issues is the ratio between surface area and volume. Take a sphere of anything and reduce its mass by 50%. That reduces its volume by 50%, but it decreases its surface area by 87.5%. To name just one issue, that’ll mean that simply scaling everything down by 50% will increase the thermal loading per square foot on the thermal protection system that you have also just reduced in thickness.

    Or, take the Mars 2018 flyby proposal that was to use a “scaled down 50%” Orion capsule. One of the key issues was that doing so isn’t as simple as reducing the size of every single Orion part by half, but also, in many cases, re-engineering the part as well. It’s essentially a whole new design. Sure, there’s some knowledge that’d transfer, but what you’re really doing is engineering and building a totally new spacecraft.

    1. Why would they need to scale down at all? Dream Chaser is supposed to ride on top a rocket without a fairing. It can’t handle riding under an airplane or is it that the rocket they plan to use is too small to put Dream Chaser in space? I can’t remember if they were talking about using a scaled down Falcon 9 or a regular version.

      1. Yes, I am a bit confused, due to dream chaser supposively being designed to include being suborbital, wiki:
        “The Dream Chaser is a reusable crewed suborbital and orbital lifting-body spaceplane being developed by Sierra Nevada Corporation (SNC) Space Systems.”

        And Dream chaser is a lifting body, one could assume is helps lift itself during Stratolaunch’s
        take off.

      2. I’d assume it all comes back to the maximum weight (220 tonnes?) that the Stratolaunch plane can carry.

      3. DC needs to be scaled down because the Startolauncher payload capacity to LEO is only ~6mt. About half of what is needed for DC, ~12mt.

        So by scaling down the design to 75% of its original dimension, the mass should be roughly halved, allowing it to be launched on Stratolauncher.

        But this is such a bad idea, and it will never happen. Stratolauncher is not economical to begin with (massive aircraft, 2 large solid stages, and a third stage with 2 RL-10 engines – it won’t be cheap!), and this mini-DC will mean that they have to start over. It ain’t happening. Especially if Dragon and CST-100 enters service.

        1. A small capsule would make far more sense. If you do scale the DC down, it would likely get ‘less fluffy’ and have a hotter re-entry as Rand puts it and also have less lift and be harder to fly and land.

          Sounds like an Ares I type death spiral to me.

          Don’t get me wrong, I like the DC and hope it gets built but this ain’t the way to do it IMO.

  6. I did say, “how much would the lifting body have to be changed” because I am aware of the square-cube law . Isn’t DC a scaled down version of the HL20 already?

    1. The HL-20 was 29.5 feet long and 23.5 feet wide. Dreamchaser is 29.5 feet long and 22.9 feet wide.

      1. Well, the article made a claim which is, in theory, testable. It claims that it saw a NASA evaluation on which Boeing scored higher on everything. It would be interesting to see that evaluation.

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