G-loading comparisons

As a followup to Benson Space’s announcement of its “low-G” reentry plan, Brian Binnie of Scaled Composites talked a bit about the planned reentry experience for SpaceShipTwo during a talk Saturday at the Heinlein Centennial in Kansas City. According to Binnie, the peak G forces on reentry will be about 7 Gs. However, in a later discussion, he said that the G-force profile during reentry will be shaped like a bell curve, with about 20 seconds where the forces are in excess of 4 Gs. (Taking 7 Gs lying flat, as passengers on SS2 will be doing, is equivalent to taking 3-4 Gs sitting up, he noted.) He added that while Benson Space’s approach could be a way to mitigate G forces, the approach Scaled and Virgin are taking has the advantage of being simpler and thus less prone to failures.

12 comments to G-loading comparisons

  • Benson Space Company emgineers believe our variable dive brakes are the safest approach because we will use two sets on separate systems. Only one set is needed for a safe re-entry, where our competition has only one large mechanical system with which to reduce velocity, and no opportunity for safe, redundant systems. We believe the simple hydraulics and mechanics of the dive brake panels, proven with over 60 years of use, are elegantly siumple and trustworthy.

    Jim Benson
    Benson Space Company

  • Peter Shearer

    I tend to agree with Mr Bensen on this. As Mike Melvil put it himself on the Discovery Channel documentary… “If we can’t put the feather up, we’re dead… It’s as simple as that.”

    And 7 G’s sounds a bit much… especially for anyone who hasn’t done a lot of aerobatic flying.

  • Peter Shearer

    Excuse me for my typo… Benson (not Bensen). I keep doing that! :(

  • Ed

    Jim….has Brian Feeney been involved in the styling of the new vehicle? It dose look like Wild Fire with wings.

    Brian was a pioneer in the industry, having introduced the “adult toy” style to airframe design.

  • Perhaps some thrill seekers would prefer the 7g experience while others like myself would favor a gentler experience. I see potential for both. However I would think that redundancy and safety features would be a selling point for all.

  • Thomas Matula

    Hi All,

    I wonder how Richard Branson’s 91 year old father and 88 year old mother will handle 7 G’s, not to mention Stephan Hawkings…

    http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2007/06/12/scivirg12.xml

    Branson: How to launch Stephen Hawking into space
    Last Updated: 5:01pm BST 12/06/2007

    [[[The plan is for Sir Richard's family to be launched in around 18 months, in the first official flight. By his family, he means "my mother, 88, my father, who will be 91, and my two children, who are not really children any more. We will be spanning three generations."]]]

  • David Michaels

    The Benson ship is a kludge of a bunch of wildly different X-plane and fighter jet parts (a wing from this, a tail from that, etc), hastily thrown together as a replacement for a lifting body based on old NASA and Russian designs. As far as anyone knows, no flight hardware exists and the whole thing is awaiting a big bucks sugar daddy or two to fund it. It is supposed to lift off vertically using a cluster of hybrid rocket engines (oh by the way, how is it supposed to remain stable in the low-speed flight regime, before airfoils become effective? Gimbled nozzles? Vernier engines? Or does is it going to zip straight up using a guide rail, like a giant Estes rocket? What kind of G forces would the passengers experience then?). There is talk of a “patented” reentry system using dive breaks, but that’s about as far as the description goes. Then it’s supposed to glide to a dead-stick landing on tiny X-15 wings. Landing speed must be at least 220 knots or so, or the thing turns into a lawn dart. This is supposed to be “safer” than the tried and true Rutan design?

    Sorry, but my money’s on Rutan-Branson.

  • G-loading comparisons…

    In response to Benson Space’s announcement about their flights only subjecting passengers to 3Gs, Brian Binnie of Scaled Composites talked recently about G-loads that Virgin Galactic’s SpaceShipTwo’s tourists will experience….

  • Dear David and others. Thank you for your interest in our vehicle. You are correct, our spaceship does use thrust vector control (TVC) during the initial 5 seconds of the ascent. It then transitions to aerodynamic controls. Ascent G forces are significantly less than air launch concepts because we have an additional 50,000 feet to accelerate to the same Mach 3 velocity needed by everyone to reach 100 km.

    Our wings and tail surfaces are patterned after the T-38 jet trainer. This trainer has been used by the USAF for the last 40 years to successfully train student pilots and the current plan is to continue to use the aircraft for another 20 to 30 years. We have a simulation of our spaceship up and running. It lands just like the T-38, which is to say it is not hard to land.

    In response to other comments, we can have a variety of motor-out situations, and continue the launch safely. We will clamp the vehicle down until all motors are firing properly (knowing in milliseconds), and can easily abort without leaving the launch pad. If we lose one, two or even three motors early in the launch, we can still safely glide back to the spaceport for a normal landing.

    As for Brian Feeney – you have got to be kidding! We only work with real, experienced and successful engineers.

    Onward and upward,

    Jim Benson

  • Peter Shearer

    Mr Jim Benson,

    Do you have anyone working on the interior design of the cabin? If not I may be able to help you out.

    I’m an Industrial Designer specializing in vehicle “experience.” Human factors, anthropometrics, environment (colors, sounds, mood creation), seat ergonomics and of course… Make it look really cool and exciting to be in!

    If you’ve seen the EADS pdf on their proposal… That’s what I can do as well. Renderings, graphics, presentations etc…

    Let me know…

    ~Peter fallingdown@hotmail.com

  • vanhumphries

    That will be some sight for the passengers when the vehicle returns to Earth and goes into vertical descent mode. It seems that the passengers will be facing the ground with all their weight on their chests.

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