23 votes

Why did the spaceX crew return to earth so soon?

Posted by Five
Tags: ask.experts, spacex, nasa, astronauts

So I’m just sitting here wondering why they returned so soon, 2 months Doesn’t seem like a very long time considering the money and preparation involved.

I did a quick search to try and find the answer without any luck, so wondering if anyone on here can shed some light on the reason.

1 comment

  1. unknown user
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    Heya! You're right this is quite a short duration mission compared to standard ISS crew rotations, which usually last 6 months, and in special cases, up to a year. There's a few reasons for this:...
    • Exemplary

    Heya! You're right this is quite a short duration mission compared to standard ISS crew rotations, which usually last 6 months, and in special cases, up to a year. There's a few reasons for this:

    1. This is the final demonstration mission that signs off and certifies SpaceX's ability to deliver astronauts to the ISS and safely return them to Earth—as part of their $2.6 billion CCtCap contract—so part of the purpose of Bob & Doug's mission is not only to reach the ISS, but also return too. Beyond that, there was not much expectation for in-orbit operations—anything they did get done onboard the ISS was a bonus.
    2. They accomplished quite a few tasks while at the ISS. Bob participated in a very aggressive schedule that saw him perform 4 spacewalks in less than 2 months, replacing batteries across the ISS's structure that store power from the solar arrays. With that complete, his work aboard the ISS was mostly done.
    3. Both SpaceX & NASA want to get on with launching the first operational mission, Crew-1, in September/October, which will be a full duration 6-month crew rotation aboard the ISS. However, this mission cannot launch until the certification review of the Demo-2 mission, including deorbit operations, takes place. Now that they've gathered that data, certification can proceed.
    4. There's technical limitations too. The solar arrays on Dragon's trunk for the Demo-2 flight were not designed to last for a full 6 month mission. Solar radiation degrades the solar cells over time, reducing the amount of power the system can generate in free-flight. They have a cut-off point beyond which NASA does not consider the system to have acceptable margins for safe Dragon vehicle freeflight. This was the primary technical constraint that would have limited their ability to stay at the ISS. In fact, there were plans to return after only a few days aboard the ISS, if necessary.

    Good question!

    45 votes