10 posts • joined Monday 18th January 2010 15:23 GMT
...they're going so very fast. Orbital velocity for low earth orbit is around 25,000km/h. In order to go that fast, you need to make your vehicle nearly all fuel. To slow back down again would take an equal amount of fuel, which means lifting it all, which means more take-off fuel. You very rapidly end up launching fuel to get fuel which needs fuel which needs fuel etc. and you no longer have a spacecraft.
Therefore, the only option is to use the atmosphere to slow down. You can do this slowly or quickly, but your limitation is how much heat the spacecraft can absorb. Even with the best insulation in the world, if you spent too long slowing down, the interior would get hot enough to cook the astronauts.
Of course, none of this is a concern for SpaceShipTwo, which only goes 4,200km/h which only generates a small amount of heating. No such suborbital craft would ever need tiles or active cooling or other advanced protection system. The 'feathering' system on SS2 is mostly concerned with maintaining a safe attitude during re-entry, when the air is thin and control surfaces have little effect.
It's the UX, stupid
I don't own a smartphone (need that battery life), but of my friends who own iphones, the reason they all do is "it just works and it's easy to use." A couple of them bought Android phones but have since gone back to iphone. Why? "it just works and it's easy to use." The only Android owners are geeks, and they geek out with each other about who's got the latest Android version or the highest resolution screen.
Apple are absolute god kings of user experience. That's why they're successful. If it was all a great big marketing con, the mask would have slipped by now.
How's the arms?
Is it just me that doesn't fancy holding their arms out in mid-air to control their computer for anything over a minute or two? I'm pretty sure it's an SAS stress position and in a grey area re: the Geneva Convention. Or something like that. A touch interface has to be down at desk level to be comfortable.