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Space Exploration/EVA at Near-Lightspeed


QUESTION: If a spacecraft is accelerated to close to the speed of light (let's say 0.9c) and then given no further acceleration, how well will it maintain velocity, assuming it avoids significant sources of gravity? Does the fact that it is traveling at near-lightspeed affect its ability to maintain velocity? If it does slow down, on what distance scale does this slowing occur?

ANSWER: Hi, thanks for writing.  Although there are things about relativity that I am not familiar with, as far as I know, it will maintain velocity the same at any speed, with only outside gravity or friction slowing it down.  However, at very close to light speed, its mass would increase, with gravity affecting it more than if that didn't happen.  Write anytime.

---------- FOLLOW-UP ----------

QUESTION: Thanks so much for the quick answer! Assuming that non-accelerated objects traveling through space won't lose speed, even at relativistic velocities, would performing an EVA and even doing repair on a spacecraft be possible at these same speeds?

Hi!  An EVA or repair is the same as at slower speeds, as long as the spacecraft is in a very near perfect vacuum and no debris in the area.  Speed is relativistic-our earth is near the speed of light relative to many objects in space, but seems still to us.  There is no universal frame of referencce.  Write anytime!

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Kenneth Renshaw


Answer basic space flight questions, research info on specific space flights. Answer questions on astronomy


Amateur astronomer and avid astronomy/space flight fan for 31 years.

Official NASA/JPL Solar System Ambassador for Arkansas and Missouri (one of about 300 nationwide). (

Numerous local and area newspapers.


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