[Moontanman]

Damn, I type too slow

[Gardamorg]

So if my craft had thousands of G's of thrust propelling it, it would be so heavy that the thrust wouldn't propel it ten times faster than if it had hundreds of G's of thrust?

Speed can create drag!

That actually makes a lot of sense.

[Moontanman]

Originally Posted by Gardamorg

So if my craft had thousands of G's of thrust propelling it, it would be so heavy that the thrust wouldn't propel it ten times faster than if it had hundreds of G's of thrust?

Speed can create drag!

That actually makes a lot of sense.

Actually it's worse than that, eventually no matter how many gees of thrust you had you would get no acceleration at all.

[Gardamorg]

Originally Posted by Moontanman

Actually it's worse than that, eventually no matter how many gees of thrust you had you would get no acceleration at all.

Yes, because it would weigh so much that the thrust wouldn't be able to push it, and eventually the weight will push against the thrust, and thats when time travel starts.

I just figured out time travel, I never understood it.

[Moontanman]

Originally Posted by Gardamorg

Yes, because it would weigh so much that the thrust wouldn't be able to push it, and eventually the weight will push against the thrust, and thats when time travel starts.

I just figured out time travel, I never understood it.

Actually you'll never get to that point, it's forever barred from our experience due to the speed of light being faster than anything can go. Of course there are certain other theories but they aren't as widely accepted.....

[Janus]

I actually already brought this up back on Page 2 of this thread, but the energy needed to get any mass up to a any given velocity is found by.

[Gardamorg]

Originally Posted by Janus

I actually already brought this up back on Page 2 of this thread, but the energy needed to get any mass up to a any given velocity is found by.

How do I deciver that, what does it mean.

I don't know formula's yet.

[C1ay]

Originally Posted by Gardamorg

How do I deciver that, what does it mean.

See Special Relativity -- from Eric Weisstein's World of Physics for some insight on what it means....

[CraigD]

Originally Posted by Gardamorg

Why not, if ten times less thrust can propel the craft at 1/10 the speed of light, why can't ten times more propel it AT the speed of light??

There’ve already been some good answers, so I’ll just try throwing in a bit of practical math.

The main thing you need to know to use special relativity in rocket (or laser-powered lightsail, or whatever) calculations is the Lorentz factor:
.
It’s used a lot. In the case of mass dilation, as a body increases in relative speed, its mass increases according to the formula .

Since acceleration is proportional to force divided by mass (), The force needed to accelerate a body by the same amount at different speeds looks like this:

Speed (c)                          Force
.01                                 1.00
.05                                 1.00
.1                                  1.01
.25                                 1.03
.5                                  1.15
.75                                 1.51
.9                                  2.29
.99                                 7.09
.999                               22.37
.9999                              70.71
.99999                            223.61
.999999                           707.11
.9999999                         2236.07
.99999999                        7071.07
.999999999                      22360.68
.9999999999                     70710.68
.99999999999                   223606.80

The closer you get to 1 c, the greater the force required.

It’s important to understand that this isn’t just theory. Although we’ve never accelerated a spacecraft to much more than .00005 c, very small bodies – electrons, protons, and sometimes more massive atomic nuclei – are routinely accelerated to high fractions of c in particle accelerators, requiring more and more force as the speed approaches 1 c.

[Pyrotex]

Originally Posted by Gardamorg

How do I deciver that, what does it mean.
I don't know formula's yet.

Gromadrag,

Formulas may look complicated, but they're easy once you get the hang.

E = mc^2 \left ( \sqrt{\frac{1}{1-\frac{v^2}{c^2}}}-1 \right )"

The E on the left refers to Energy, measured in Joules.
The m to the right of the = refers to Mass, the mass of the spaceship in kilograms
The C squared means the speed of light in meters per second, squared. The creates a very, very large number
The big crooked thingie is the symbol for square-root. So, we will take the square root of everything under it.
Under the square root thingie we have a fraction within a fraction, and the inner-most part is V squared divided by C squared.
V is the velocity you want the spaceship to travel at.
C is the speed of light again.

Does this help?