In an interview Richard Branson says that Virgin Galactic is working to replace SpaceShipTwo’s hybrid engine.


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In an interview Richard Branson says that Virgin Galactic is working to replace SpaceShipTwo’s hybrid engine.

So for instance, the initial rocket which I’ll be flying on to space will be thrown away afterward. Within six to nine months, we will be using rockets that will have capability of being used maybe up to 1,000 times, but definitely up to 100 times. That will bring the cost of space travel down dramatically.

This timing fits with their new schedule for the first commercial flights of SpaceShipTwo sometime late in 2014. I suspect they are hoping to fly the ship a few more times with the troublesome hybrid engine, partly for engineering research and partly to keep interest up in the company, and then switch over to a new engine.

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10 comments

  • Kelly Starks

    Good idea. hybrids (and solids) are hard to scale up reliably, and trash themselves after one flight – and make for rough ride. Liquids have better safty, durability, re-useability, and performance.

  • wodun

    Raises some questions about how they got this far with the current engine and how developing a new one will work out.

  • Dick Eagleson

    The most straightforward source for a new engine would be their Mojave Spaceport neighbor XCOR, though the SpaceX Draco is also an outside possibility.

  • Not sure I agree that solids are hard to scale reliably. Shuttle used solids for primary boost, and the one failure was forseen and avoidable. All US ICBM’s use solid rockets, and reliability is a primary concern. I agree with your assessment of the advantages of liquid-fuel rockets, but I’m wondering where there is sufficient storage space on SpaceShipTwo, and how the added mass of fuel will affect payload. If seating has to be reduced, then any cost savings from re-usability will be compromised.

  • Pzatchok

    Hybrids are hard to use. Or at least use the way they want to.

    I don’t know why they don’t just make up some large JTOW type solid rockets that they can jettison off after making space.

    Then just using a liquid fuel rockets of even hybrid jet engines for landing.

  • Kelly Starks

    >..Not sure I agree that solids are hard to scale reliably…

    The solid parst are flexible, and the burn rate varies with exactly how they flex. Calculating the extra movement of a extra scale material while its burnering – and the burning throwing around shockwaves disrupting oxidizer flow…. You can do it, but its nor easy – and the result makes for a rough ride.

    Solids are used as a quick and dirty solution for launchers

    > All US ICBM’s use solid rockets, and reliability is a primary concern…

    Actually storability is the big concern. Once cast the solid motors are relatively insensitive to being left that way for years – or decades. Liquids you worry about moving parts lubricants drying out, things leaking out in confined silos/launch tubes, etc. Solids are a bit dangerous to be around – but a good mix can be parked for years to decades without degrading.

    >.. I’m wondering where there is sufficient storage space on SpaceShipTwo, and
    > how the added mass of fuel will affect payload….

    The mass of a similar performance liquid will be less due to higher ISP of most any liquid system that I can think of – though I’m not sure how bulky it would be in comparison?

  • Kelly Starks

    Sadly Rutan made the basic mistake of assuming hybrid’s were innately completely safe, then assumed his company could build their own just fine. These mistakes cost years and lives – and likly contributed to Branson informing them that scaled wouldn’t be involved in the next space ship 3 project, and Rutan deciding it was time to turn the rest of Scaled over to Northrup and retire.

  • Thanks for your thoughtful reply. In the context of ICBM’s, storability and reliability are essentially the same thing. When you need a missile, you need it RIGHT NOW, even if its been sitting in a silo for a few decades. I’m sure the Titan II maintenance requirements caused more than a few grey hairs.

    For repeatable, reliable access to space, liquids are the way to go, for sure. The tradeoff is the failure mode set size is much larger.

  • Kelly Starks

    >..The tradeoff is the failure mode set size is much larger.

    Not sure about that. Anyway, not a lot of failures in professionally made liquid engines. Solids seem to stil fail more often.

  • Kelly Starks

    I think Branson would probably rather go with one of the more established firms. Having to wait now over 10 years for SS2 due to Rutan’s struggling with the engine etc, I think Branson would be eager to move up to the bigger,more solid and capable, suppliers.

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