3
$\begingroup$

Is there any safety advantage/disadvantage to a particular attitude in space - lined up with the sun, sideways, tumbling or spinning?

Assuming a long cylindrical space craft on a long journey within the solar system. It is subject to solar radiation, meteoroids/debris and cosmic radiation, etc.

I could see a possible advantage in minimizing shielding materials if lined up with the sun but the other things seem unaffected.

$\endgroup$
6
$\begingroup$

Radiation

As you have rightly noted, a long cylinder pointing end on to the radiation source (probably the sun, especially during periods of high activity), can be shielded by a smaller, and thus lighter, shield. On the other hand if you need shielding facing all directions, then a sphere is a better choice.

(Micro-)meteorites

The spaceship is moving fast, in some direction given by where it is, where it wants to be, and orbital mechanics. Dust, rocks and debris will be moving somewhat at random, but will tend to have a preferred direction. They mostly go round the sun/planet/moon the same way the rest of the solar system rotates, and there won't be many rocks on orbits which pass through another body. So in some cases, there will be a direction from which more rocks come than others. It makes sense to point one end of the long cylinder in that direction to reduce the chance of being hit. Note that the ISS is constructed/orientated with this at least partly borne in mind.

Solar heating

This isn't something which drives the orientation as much as something which might make it unsafe to vary from the orientation the designers planned. You probably have solar panels which want to face the sun, and radiators which don't. If you don't keep an orientation which allows them to do so, and you don't have alternate energy sources/heat sinks, you're going to have problems. Similarly, if the design was expected to face the sun and ends up spinning, the rapid heating/cooling cycles might do bad things to the skin. If it was intended to spin and is now static, thermal management could be difficult.

Stability

A 3D object spinning in space is stable when spinning in some directions, but not others. Don't be this shape. It would be wise to pick a rotation which is stable, even if stuff moves around inside the ship. Otherwise you'll be wasting propellant or electricity (on reaction wheels/gyros) staying stable, and have additional risks if that subsystem fails. This isn't about the external shape as much as it is about the distribution of mass inside that shape.

Artificial Gravity

Since you ask about a large ship, and are concerned about radiation, I wonder if you are thinking of a future manned ship. If so, you'll want to set the spin up to give reasonable gravity, uniform gravity within the crew compartment, and minimal Coriolis effect. That way your astronauts are less likely to misjudge it and get hurt, or spend too much time throwing up. Overall safety is going to depend on them making good decisions.

There are probably other considerations I haven't though of...

$\endgroup$
  • $\begingroup$ Great response. I hadn't thought about the thermal effects before although I now recall this being an issue on some past flights. $\endgroup$ – A. Flowers Dec 7 '16 at 19:59
  • $\begingroup$ Another consideration for attitude control: gravity gradient torque. The difference in gravitational pull across different portions of a vehicle creates a net torque on the vehicle that must be countered to maintain an arbitrary attitude. This puts a steady drain on attitude control resources. Choosing an attitude that minimizes (or even completely nulls out) that gravity gradient torque leaves you with greater control authority to counter any unexpected perturbations. $\endgroup$ – Tristan Dec 8 '16 at 16:55
  • $\begingroup$ Possibly one to add to your list - the view through any windows - also mentioned here. On a long trip it might be nice to see the Sun through a window once in a while, especially if getting farther and farther from it. Watching the Earth + Moon system get smaller and smaller bye eye, then long focal length camera lens, then telescope might have good (or bad) psychological effect, ditto the destination body growing larger and larger - like in several SciFi stories and films. $\endgroup$ – uhoh Dec 13 '16 at 10:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.