Flight International provides some relatively new details about the performance of SpaceShipTwo, based on comments made by Virgin Galactic president Will Whitehorn and Scaled Composites’ Brian Binnie at a space tourism forum in London last week. According to the report, SS2 will fly to an altitude of 140 km and experience 7 g’s on reentry. However, the “shuddering” experienced by SS1 during the end of its engine burn–caused by the intermittent injection of nitrous oxide oxidizer as the tank neared depletion–may still exist in SS2 because of “its slim design margins”. (The article does note that SS2 will use a “new hybrid rocket motor”, which is not surprising given both that SS2 will be larger than SS1 and the deteriorated relationship between Scaled Composites and SpaceDev, which built the hybrid motors used by SS1.)
The 7-g reentry is a little surprising, because that’s a lot of acceleration to expose tourists to, although that’s probably not avoidable given the higher altitudes SS2 will fly to. That will make the development of seats that can protect passengers from the worst accelerations all the more important. One odd point at the end of the article: the increased downrange of SS2 “could enable it to land at Roswell instead of the New Mexico South West Regional Spaceport near Las Cruces.” But why would you want to do that? The purpose of suborbital space tourism is not to go from point A to point B, but to go from point A to point A via space. Landing at another airport only increases logistical complexities and costs.
Why has the relationship between Scaled Composites and SpaceDev deteriorated? And who is then going to build the rocket engine for SS2?
I’ve spent the last two years wondering how they can reduce the 5G deceleration for the tourists… now they’re going in at 7G’s??? I did 4g’s in a biplane once… thought I was gonna die. It’s nice that they want to go to a higher altitude (better view, increased curvature of the earth, more time weightless) but I’d like to go to space and can’t afford the $200,000 price tag. Can we get a discount if we only get to 62 miles? SpaceDev is a competitor so it’s not surprising that Scaled cut their ties as soon as SpaceDev was no longer needed. Scaled actually did most of the developement work on the hybrid rocket and retains the design data. They didn’t have the facilities to build their own rocket then, they do now.
Forget about downrange, they should make White Knight2’s cockpit the same size and sell 6 tickets (cheaply) to ride in the mothership and witness the launch from 50,000 feet. I’d pay for that!!! Don’t you think that’d be fun?
The effect of G loading on the body depends on the direction. If you’re talking about positive Gs (the force is generally from head to foot, as in an inside loop), then sustaining 7Gs is tough. If you’re talking about negative Gs (blood rushes to the head, as in an outside loop), then 7Gs would be unbearable. However, the Gs can be aligned from the front of the body to the back both during powered climb and reentry. G loads in this manner are much more bearable. If the seats are perpendicular to the velocity vector (upright during powered flight, reclined during reentry), then 7Gs shouldn’t be too bad.