What's the best feasable method to gain near-lightspeed and brake again?

Question

As it says at
http://answers.yahoo.com/question/index;_ylt=AiCLAEHCFHyR.YIoRV1PvFPsy6IX?qid=20070520173937AAQfRBc
, there's no method known to gain deeply relativistic speeds and brake again.
I assume 'deeply relativistic speeds' includes 99.99% of lightspeed. That book was written in 1989.

The question is: is there in 2007 still no known feasable theoretical method to travel at 'deeply relativistic speeds' (including braking on time)?

And: can fatal damage by micrometeoroids be feasable avoided at such high speeds?

Answer 1

Solution:

1) Put Bill Clinton on the treadmill

2) Have Jessica Alba stand directly in front of him wearing a bikini & holding a double-double with cheese.

Upon expending all of his energy, Bill will collapse and form a black hole around which we can slingshot to achieve near-light speeds.

Answer 2

I assume you're asking about something big, like a satellite, rather than something small like a particle.

The obvious would be to not use rockets or any other method where the propellant is used as the action-reaction pair.

For instance, the reason why jets are so much more efficient then sub-space rockets is because they use their fuel to pressurize the air already in the atmosphere.

That paradigm could be applied to moving a satellite. Rather than push the thing as an action-reaction pair of fuel, the action-reaction pair could be material already in space.

Outside of the solar system, it is estimated that there is a mass density the equivalent of about 1 atomic mass per cubic centimeter. The mass would need to be scooped into a particle accelerator, acellerator to near c, and then dispensed from the back of the satellite.

The faster the satellite accelerates, the more mass it can scoop and assuming there is enough (presumably nuclear) energy to run the accelerator, it would be possible to bring the satellite to a large fraction of the exit particle speed. That same method could be used to brake it, by turning it around and doing the same thing in reverse.

From a physics view, there is very little difference between 2007 and 1989, we don't have that much new information since then. But I don't know of any inherent limitation on using particle accelerators as engines. A little calculation using the relativistic momentum and the Pointing vector shows it's possible at least from a physical point of view. (Politics and economics are a whole different issue completely of course.)

As for the last part of your question, a speck of dust at space shuttle speed isn't too dangerous. A speck of dust at 0.7c though, is another issue completely ... catastrophic.

The most fuel-efficient way I could think of shielding a satellite at high-speeds would be by exploiting the Lorentz relation between E and B fields. At speed, a high Gaussian field on the skin of the satellite would transfor to a high magnetic field, which should be enough to easily divert ferromagnetic material, and with high enough field field, dia and paramagnetic material too, though stochastic oscillations in the E-field.

Answer 3

The answer to the ? in your 2nd §:

"The question is: is there in 2007 still no known feasable theoretical method to travel at 'deeply relativistic speeds' (including braking on time)?

is easy because you used the word 'theoretical': just accelerate at ~ 1g for ~1year and you will be there. (-1g) to brake........
.........and no, damage from µmeteoroids cannot be avoided. Not to mention fist sized ones.

Answer 4

I believe the best way would be to use the gravitational pull of a large planet, Jupiter would be the most feasible since its not hot like our Sun, and it doesn`t have a ring around it like Saturn. You would have to plot the number of orbits and shape of those orbits to maximize the slingshot effect, and the direction you want to travel. To slow down you would use another Planet with a good gravitational pull and de-orbit like the shuttle does basically. Until we know more about black holes, and matter, anti-matter, we are not going to obtain anything close to the 186,000 miles per second you are talking about.