# Space ships turning+time dilation

1. Mar 28, 2013

### willbell

I am planning a hard-ish science fiction novel and I was wondering about space ships turning when going at extremely high speeds (in my case .33c). My question is can ships going this speed turn without sending the crew through the windshield so to speak? If its a stupid question let me know because that is just as useful to know.

My second question is in regard to time dilation, when things go at higher speeds, time slows down for them, I am wondering if for example with the speed I used above (.33c) would time slow down 33% compared to a non-moving object/observer? And if not how would you calculate it?

2. Mar 29, 2013

### Staff: Mentor

With sufficient time, acceleration can be low. With 1g, "stopping" (or making a 60°-turn) would need about 10^7 seconds or 4 months. With 2g, you just need 50% of that, and so on.
Time dilation follows the (inverse) gamma factor $$\frac{1}{\gamma}=\sqrt{1-\frac{v^2}{c^2}}$$
For v=.33c, this is 0.944... or 5.6% slower passing of time. You need more speed to get significant time dilation.

3. Mar 29, 2013

### willbell

Thanks! I believe that just about covers it.

4. Mar 29, 2013

### Xtrapper

As to turning your space ship at a forward speed of .33c, [how ever far you turn], the point I believe for your book to considered is simply your power available to make the turn, if you have accelerated at 1g. For a long time to say .33c. as 1g, was the max power you had, [then its still the max power you have], all you can do is turn the ship side ways and power on at 1g. To make the turn and the max stress you can put on the people in the turn is still 1g, the change in direction doesn't matter, [it's not an air craft where it built up speed slowly and then used the air to turn fast and can turn people to mush], changing direction in space does not have the problem you have in the air unless you have a really great amount of power to do the change with, an amount of power that would mush you just accelerating in a strait line.
As this is only SF, if this book is a first attempt in your story to get up to these speeds, consider creating, [for a new SF. Issue], a problem being found in the turn of the ship, maybe some bad effect in the changing of the speed and directions in the ships different parts, [the end and front turning at a different rate than the middle with some problem-effect, arising in that small difference in motion], try finding something like that not having been done before in SF. SF. reader,Trapper.

5. Mar 29, 2013

### willbell

Thank you Xtrapper, my main reason for asking was I was thinking about a high speed battle, I'm probably going to just lower the speeds (plus adding a little softness to my story), although I think I'm going to save that last paragraph as an idea for any further stories that I write.

6. Mar 29, 2013

### Staff: Mentor

Hard-ish science fiction and space battles are tricky to combine.

Manned crews would not just take months, but also extreme distances to accelerate to those velocities - you are far away from anything interesting (planets, asteroids, ...) long before the speed reaches a significant fraction of c.

7. Mar 29, 2013

### willbell

Agreed now, I found a calculator just now that showed how acceleration at 1 g works. So now I'll just determine it using that and 1 g of acceleration, so much slower speeds.

Last edited: Mar 29, 2013
8. Mar 30, 2013

### Staff: Mentor

If you want it to be truly hard sci fi you should look up the rocket equation and take that into account. In short: to increase/decrease your payload's velocity significantly you're going to need a lot of fuel. But then you have to bring fuel for that fuel and then fuel for that fuel etc etc. This was a killer for another thread we had on a similar subject (check out post 6 especially):

9. Mar 30, 2013

### willbell

I'm not passing through interstellar space, I have Faster-than-light "jumps", not at all realistic, sort of half way between Soft and Hard scifi. Why I was wondering about it was because their faster than light drives are knocked out, I have a plan now that won't involve further than a couple AU ever at a time.

10. Mar 31, 2013

### Xtrapper

question

Ok not to take up a lot of time but what could be the effect of a say light weapon between two closing ships, [ships closing with each other at a speed of say .10c, each, the weapons fire is closing between the ships then at 1.20c], the question is at what point in time, at which event, does the weapon actually have any effect, is it at the point where the weapon fire reaches the ship at 1c, or before that where the weapon-light, is actually moving at 1.20c, and reaches the ship?
These are, or it seems, two different actual points in time and space that should exist with different realities, effects, outcomes, 2, events at the same place but at different times, 1, event with some effect, 1, event with no effect, [the fact of a very small time between the 1g, and 1.20, event does not seem to me important].
Light moves at c. always, (Ok), but the closing speed of the ships changes that-but does not change the speed of lights at the same time, so again, without a Smoke and Mirrors Explications, does any one actually know if the effect of the weapon is going to be at the point of 1c, or at the point of 1.20c, contact, (I do realize that Smoke and Mirrors may be all we have today for an explanation).

11. Mar 31, 2013

### willbell

I hadn't considered that. If I understand the question my guess would be that you have to look at it as "light produced at x time at x point in space hits ship at y time at y point in space" and that it would show the light to be travelling at 1c. Not 1.2c.

12. Mar 31, 2013

### Staff: Mentor

Post 6 used 0.1C as an example, I thought it relevant as your craft are meant to be able to accelerate to and from 0.33C. But it doesn't matter too much if you're going for soft SF.

13. Mar 31, 2013

### willbell

I try to aim for hard but it just doesn't let you have any fun.
I haven't thought too much about deceleration yet.

14. Mar 31, 2013

### Staff: Mentor

Classic sort-of-hard-SF approach is to simply flip the ship the other way and turn on the propulsion. On another note I'd recommend looking up the Dread Empire Fall trilogy and the Lost Fleet series. Both are military SF featuring a lot of battles in space. The latter is a bit soft (ships have inertial dampeners for example) but the former is quite good at taking into account things like the effect of acceleration on the crew.

15. Mar 31, 2013

### willbell

I'll look it up, thanks!