But dreams of civilian spin-offs are at least 20 years away, said NASA officials, who are betting the program will first lead to a more durable, cheaper workhorse for the space fleet.

• NASA称，其至少要在20年后才能用于民用飞行。他认为，该计划首先将导致更持久、更便宜的推进器的出现，以用于宇宙飞行器。