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posted by chromas on Friday April 06 2018, @03:41PM   Printer-friendly
from the when-is-the-flutter-test? dept.

Virgin Galactic spacecraft performs the first powered flight since fatal 2014 crash

Richard Branson's fledgling space tourism company Virgin Galactic performed a powered flight of its spacecraft today, the first since a fatal crash in 2014.

Virgin's spacecraft is unlike others because it is launched mid-flight by a larger plane called White Knight Two. This particular version of the spacecraft, dubbed SpaceShipTwo VSS Unity, has performed seven glide tests since it was built in 2016. Like those previous tests, it was carried high above the Mojave Desert by White Knight Two and released at 46,000 feet. But today, pilots Mark Stucky and Dave Mackay fired Unity's engine and continued skyward.

The spaceplane's engine burned for 30 seconds, pushing the Unity supersonic to Mach 1.87 before the engines cut off. It coasted to 84,000 feet before gliding down again for a safe landing at the company's spaceport back in Mojave. White Knight Two safely touched down roughly 30 minutes later.

Also at CNN and Bloomberg.


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  • (Score: 2, Informative) by Anonymous Coward on Friday April 06 2018, @10:24PM (6 children)

    by Anonymous Coward on Friday April 06 2018, @10:24PM (#663563)

    One of the basic equations of motion is
    V*V = U*U + 2 * a * S

    V final velocity
    U initial velocity
    a acceleration
    S distance
    Using MKS system, you don't need any conversion factors.

    Starting from 0, with V = 1000 m/s

    a * S = 500000
    If you can stand 10G, call it 100 m/s/s then S = 5000m. So to get a 1 km/s launch you need 5km of railgun,

    But it gets worse. 1 km/s is useful, but it won't get you anywhere near orbit.

    7 km/s would be enough to get you to LEO, needing only a small thrust to circularize the orbit.
    7000 x 7000 = 2* a * S
    If a = 100 (= 10G) then S is 245 km. For the yanks, that's 153 miles of very substantial railgun.

    If you don't think you can stand 10G for 70 seconds, then adjust a and S accordingly.

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  • (Score: 1, Informative) by Anonymous Coward on Friday April 06 2018, @10:46PM

    by Anonymous Coward on Friday April 06 2018, @10:46PM (#663572)

    Also, if you try and build anything like that, the Israelis will come and assassinate your engineers, (see Gerald Bull)

  • (Score: 1, Interesting) by Anonymous Coward on Friday April 06 2018, @11:47PM (1 child)

    by Anonymous Coward on Friday April 06 2018, @11:47PM (#663586)

    Starting from 0, with V = 1000 m/s

    Note that this is a mistake. If the railgun is built on the equator as OP suggested then the initial velocity is not zero -- it is about 465m/s at sea level (perhaps more if you can build at a higher altitude).

    The railgun will still be huge. It probably doesn't make any sense to go straight to 7km/s with one. But a launch system like this requires no fuel on the vehicle itself -- this is a big win even if the railgun only accelerates the rocket by a small amount -- assuming you can actually build it and have it work reliably.

    • (Score: 0) by Anonymous Coward on Saturday April 07 2018, @12:59PM

      by Anonymous Coward on Saturday April 07 2018, @12:59PM (#663729)

      Really? You're going to hit the starting end of the railgun already travelling at 465 m/s? I'd watch that on youtube.
      Or, here's a thought, maybe the acceleration, velocity, and distance figures are relative to the planet you and the railgun are standing on when you start.

  • (Score: 3, Informative) by bzipitidoo on Saturday April 07 2018, @12:25AM (2 children)

    by bzipitidoo (4388) on Saturday April 07 2018, @12:25AM (#663598) Journal

    Several problems. I suspect people can't take 10G for 70 seconds. The longer the duration, the less Gs a person can take. 6G may be the limit for over 1 minute. In that case a = 60. Then, to reach 7 km/s, S must be 408.3 km.

    But, moving anything at such speeds in the lower atmosphere will generate a lot of heat. Near sea level, shells fired at speeds of 6 km/s tend to burn up in the air before they reach their target. I don't know how much difference 6000m of elevation makes, but I doubt that's high enough to avoid this problem.

    No, I had in mind that the railgun would assist, rather than provide all the momentum. Anyway, while workable, it's probably too costly.

    • (Score: 1, Interesting) by Anonymous Coward on Saturday April 07 2018, @01:10PM

      by Anonymous Coward on Saturday April 07 2018, @01:10PM (#663730)

      Yeah, I worked out a long time ago that the optimum was probably about 60 km of rail with an exit velocity of about 3 km/s on top of a mountain. That's fast enough to let you use a reasonably robust and cheap single-stage-to-orbit vehicle without absolutely insane engineering on either the railgun or the launch vehicle.

      If they ever get that hypersonic scramjet working, you could go back to two stages with an airbreathing first stage and put a bigger load into orbit with the same launch mass.

    • (Score: 2) by corey on Thursday April 12 2018, @09:40PM

      by corey (2202) on Thursday April 12 2018, @09:40PM (#666169)

      Do it.

      Come up with a proposal and get some venture funding.

      This concept is good but engineering is a challenge. Just like the hyperloop.

      Hundreds of km is just too much but you could expect to get to Mach 1 on a rail launcher.

      It'd be interesting to design, build and test a vehicle that would withstand up to 10G for that period too.