Redshift occurs whenever an observer moves away from (shifted to the red) or approaches (shifted to the blue; blueshift) an object that emits radiation and the other way around.

Traveling towards something that mostly emits radiation in the spectrum of visible light like our sun will shift it into spectra of higher energy. Going from ultra-violet over x-ray to gamma depending on the speed on a space ship.

How would a space ship have to be designed to protect the crew and equipment from increasing radiation as its speed increases?

A cylindrical object with shielding at its top with the crew directly behind it? Or should the crew be as far away as possible from the space ship's top? Would a different shape be more effective for shielding against radiation?

  • 4
    $\begingroup$ While a really great question, I believe it is off topic for this site because, we really don't have a feasible means to get a space craft to the speed required to consider the problem. $\endgroup$ Jul 21, 2013 at 18:37
  • $\begingroup$ ;) The question won't go away unless deleted by someone else. At least for now I'm not planning to delete it. It's an actual spacecraft engineering question. Arguably not relevant today or in the near future. $\endgroup$
    – bastik
    Jul 21, 2013 at 19:26
  • $\begingroup$ I like the question. I'll have to do some calculations to see how much shift a typical spacecraft might see though -- I suspect it is small. Also, I thought most of the hazard came from charged particles. $\endgroup$
    – Erik
    Jul 21, 2013 at 22:33
  • $\begingroup$ If you want to go even further with the fanciful notion, you can read the physics question on the topic about cosmic microwave background becoming scorching physics.stackexchange.com/questions/34673/… $\endgroup$
    – AlanSE
    Jul 21, 2013 at 23:47
  • 4
    $\begingroup$ Personally, I think limiting the scope of this site to "space exploration in the nearest future using only technology we have developed currently" is entirely misguided. If we don't look into the future and don't start digging at its problems now, we will never reach it. $\endgroup$
    – SF.
    Jul 22, 2013 at 9:03

1 Answer 1


So, there are two aspects to this problem. The first is one that we deal with today on a regular basis, that of the Doppler shift of a spacecraft orbiting the Earth, or otherwise moving towards/away from the ground-station. This is the same phenomena as the Red Shift, just at a lower magnitude. Why is this important? For a 150 MHz uplink, the Doppler shift is around 3 kHz for a satellite in LEO. That actually is a channel in some modes of communication. The higher the frequency, the larger the jump, such that an FM channel could entirely be passed, if the doppler is not taken in to account.

So, how do you correct for that? Basically, calculate what the doppler should be, and send at a frequency such that the spacecraft will get the right signal. Additionally, you can build a control circuit such that the detected frequency window can drift slightly, according to the carrier frequency.

As for the second problem, that of radiation becoming higher energy as you approach it. How is this managed? First of all, let's see where it would become an issue. Let's assume a frequency of 10^15, which is in the realm of visible light. The energy becomes ultraviolet at an increase of about 10 fold frequency increase. To do that, you have to be moving at 0.9c, thus, you are hit by the wavelength 10 times more (1/(1-speed)), giving you an increase of 10 in frequency. That is a very significant speed. Furthermore, this will only be coming from the front half of the spacecraft, the back half will see a 50% decrease in frequency, which is harmless (See this calculator)

So, what else is a spacecraft going to need to do that is moving that fast? There must be a way to protect it against small particles, even the most minute particle would cause issues at that speed. That would involve some physical shielding, no doubt, on the forward site. In addition, there is high amounts of radiation anyways in space, which will need protection.

The bottom line is, radiation from moving this fast isn't likely to be a problem. It will likely be solved when dealing with other issues the spacecraft will have.


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