行星际航行 Interplanetary spaceflight
（重定向自Interplanetary propulsion）
行星际航行或行星际旅行指在行星系内的行星之间旅行。实务上，此类的太空航行局限于太阳系内的行星之间。载人飞行的行星际航行必须维持生命保障系统，成本非常高昂；而重量较轻的太空探测器则是太阳系内行星际航行的主力。
Interplanetary propulsion
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Interplanetary spaceflight 行星际航行
（重定向自Interplanetary propulsion）
![View from MESSENGER, as it flies by Earth en route to Mercury](/Images/godic/202501/20/-Mdis_depart_anot.ogv1104.jpg")
![](/Images/godic/202501/20/Hohmann_transfer_orbit1104.jpg"){kind=spacer}
![Over-simplified example of gravitational slingshot: the spacecraft's velocity changes by up to twice the planet's velocity](/Images/godic/202501/20/Gravitational_slingshot.svg1105.png")
![Apollo Command Module flying at a high angle of attack to aerobrake by skimming the atmosphere (artistic rendition)](/Images/godic/202501/20/Apollo_cm1105.jpg")
Interplanetary spaceflight or interplanetary travel is travel between planets, usually within a single planetary system. In practice, spaceflights of this type are confined to travel between the planets of the Solar System.