Actually, that's all you need to do all kinds of interesting sub-orbital work. They've been flying to much higher altitudes, recently. There are a lot of subtl

Actually, that's all you need to do all kinds of interesting sub-orbital work. They've been flying to much higher altitudes, recently. There are a lot of subtleties in liquid-fuel rocket engines. Simply getting them to ignite reliably and to re-start were seen as a Big Deal, only a few years ago.