Unlike commercial planes, which can use the lower atmosphere's oxygen to give their fuel systems a boost, suborbital rocket planes use liquid oxygen tanks to compensate for the thin air and get the thrust they need. (discovermagazine.com)
PoSSUM plans to use XCOR Aerospace's suborbital rocket plane Lynx; two people fit in its flight pod. (discovermagazine.com)
The SpaceLiner, a hydrogen - powered rocket plane conceived by the German Space Agency, could someday carry up to 50 passengers through the upper atmosphere. (discovermagazine.com)