The advantage of the balloon is that it will be cheaper than a space plane or rocket.

气球的优点是它比航天飞机或火箭便宜。

youdao

An alternative to the space shuttle was the original space plane of the Eisenhower era.

在艾森豪·威尔时代，最初的设想是空天飞机，而不是航天飞机。

youdao

The Pentagon has repeatedly said that the space plane is simply a “test bed” for other technologies.

五角大楼曾多次表示，空天飞机仅是一个技术“试验床”。

youdao

And so begins the first powered flight of the experimental plane designed to take man to the edge of space.

VOA: special.2010.07.07

There were new designs for the plane's rocket engine, landing equipment and the small rockets needed to move it in space.

VOA: special.2010.07.07

They wanted a plane that could test conditions for future flights into space.

VOA: special.2010.07.07

Without a military space plane, there is no way the Air Force can become the Air and Space Force.

CENTERFORSECURITYPOLICY: Giving Saddam Space

If your secret space plane's in orbit and doing its secret thing well enough, why bother bringing it home?

ENGADGET: Air Force X-37B space plane books additional time on orbital cruise, orders another margarita

The programs in question are the Clementine II asteroid intercept experiment, the Army's Kinetic Kill Anti-Satellite Weapon and the Military Space Plane.

CENTERFORSECURITYPOLICY: Clinton Policies Would Disarm U.S. Space Capabilit