Warp drive may actually be possible, NASA scientist says

http://www.ksl.com/?sid=22195854&nid=1012&title=warp-drive-may-actually-be-possible-nasa-scientist-says&s_cid=queue-5

by kausikram • 14 years ago

52 31 14 years ago

Tossrock• 14 years ago

> "A trip to Alpha Centauri would take about two weeks. Traveling as fast as we are now currently able, it would take tens of thousands of years."

This isn't true. Nuclear pulse drives built with currently available technology could achieve .05C [1], meaning a 4 light year trip would take ~80 years.

[1] http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsi...

danielbarla2• 14 years ago

IIRC, that assumes we don't want to decelerate. Adding the fuel to decelerate also increases the fuel needed for the original acceleration itself, which then quickly becomes less feasible. In any case, I'm guessing they were referring to "current, tried and tested" technologies.

Edit: I'm also having a slight chuckle at the estimated costs presented. Somehow, I'd think that just getting 40,000,000 t of spaceship into orbit would cost a bit more than 1 year of US GNP.

wcoenen2• 14 years ago

The mass added by the "fuel" of the orion nuclear pulse drive is negligible: a nuclear bomb has very little mass compared to the impulse boost you can extract from it.

You could literally lift a city-sized space ship to orbit on the cheap with this technology. The problem is the nuclear fall-out for those left on the ground.

InclinedPlane• 14 years ago

To decelerate you'd use a magsail or an m2p2 type system. This is vastly more mass efficient than simply thrusting in the reverse direction.

ch0wn• 14 years ago

Previous discussion: http://news.ycombinator.com/item?id=4534359

WalterBright• 14 years ago

One issue about warp drives that I never see mentioned is one has to be careful one is not creating a perpetual motion device.

Consider a warp drive that transports you from, say, earth's orbit to pluto's orbit. Now, you fall back towards earth's orbit. This means that the warp drive, in order to not violate conservation of energy, must require at least as much energy as the potential energy difference between the two positions.

yk2• 14 years ago

Conservation of energy may or may not be valid in general relativity, at least in a naive understanding of conservation of energy. The technical explanation for this is, that conserved quantities are related to geometrical symmetries via Noethers theorem [1], and on a curved background these symmetries may or may not be there. ( A rather handwaving explanation would be, that there is no straightforward way to define the energy density of a gravitational field.)

In fact it is possible to build a perpetuum mobile by just filling some region of space with dark energy. This region of space will then expand at constant energy density, therefore creating energy.

[1] https://en.wikipedia.org/wiki/Noether%27s_theorem

maxerickson2• 14 years ago

"In fact it is possible" is a pretty strong way to talk about moving something that might not exist.

egypturnash• 14 years ago

I think you're describing a feature, not a bug. Especially if you can figure out a way to derive energy from the fall.

maxerickson2• 14 years ago

It seems if you had the power to violate causality and worked hard enough at it, that future event would have propagated into the present day past by now.

Maybe that's really what killed the dinosaurs.

shin_lao• 14 years ago

The article doesn't mention exotic matter. Did they find a way to build an engine without exotic matter?

panacea• 14 years ago

No. See: http://news.ycombinator.com/item?id=4534359

keyle• 14 years ago

Can someone explain what happens to time while you travel this way?

Is your family at home going to be older when you come back from one of those trips?

jonnathanson3• 14 years ago

Simple answer: probably not. You wouldn't experience time dilation in this scenario, because the ship itself isn't actually moving faster than light speed. In fact, it's not moving very quickly at all. It's bending space around itself, while remaining within a flat and undistorted region of space inside the bubble. With respect to objects inside the bubble (its own frame of reference), the ship is not moving faster than light. (A beam of light inside the warp bubble will still travel faster than the ship, for instance).

Basically, the ship is able to traverse distances faster than light can, but it isn't actually moving faster than light.

shanelja2• 14 years ago

Question 2: What would happen if you, whilst within this bubble, throw a coin attached to a piece of string out of the space ship, while still connected to the ship by the string and the coin exits the bubble?

For instance, assuming the 'string' was made of a tough alloy, would it snap and the coin remain where it was at that time, would the ship be dragged back to where the coin is, or can the question not yet be answered by science?

I ask because, presumably, if the coin can exit and be fine, this could be the basis for some kind of inter galaxy bus, no need to slow down the bus, merely drive your spaceship off the bus and exit the bubble when at your destination.

EthanHeilman• 14 years ago

>You wouldn't experience time dilation in this scenario, because the ship itself isn't actually moving faster than light speed.

Time dilation occurs at speeds far less than the speed of light. For instance GPS satellites and jet planes experience measurable time dilation.

I am very curious about the time effects of such a drive. Does the ability to warp space using such a device necessarily include the ability to warp time? Is it possible, within a frame of reference, to locally reverse the arrow of time and thereby reverse entropy within that pocket?

>A beam of light inside the warp bubble will still travel faster than the ship, for instance.

But that beam of light seen from outside the bubble will appear to travel faster than the speed of light.

gus_massa• 14 years ago

Space-time is a single entity, so it's not possible to distort the time without distorting the time. For example, if some astronauts are traveling in another rocket with a constant relative velocity (< c) they would see same of the original space distortion as a time distortion. And if they go fast enough and in the correct direction, they would see that the "faster than light ship" is traveling backward in time (in their time system, the arrival day will be before the departure day).

I don't know enough special relativity to do the calculations, but if this device is constructible I would expect to have huge modifications in the time coordinate. Just in case, say goodbye to everyone before leaving.

brudgers• 14 years ago

I am not a physicist - My understanding is that it is information that is limited to the speed of light. So the technology for sending people to a nearby star tends to be analogous to the to that between Clarke's hominids and the obelisk rather than that between Captain Kirk and Star Fleet.

Warp drive will allow humans to pollenize, not colonize, other planets.

Tipzntrix• 14 years ago

If we can't move the spaceship fast enough, we'll move the space around it! No wonder all the sci-fi movies show the area around warp speed ships distorting. They must have been onto something. I don't want to know how a human could ever survive that though.

powertower• 14 years ago

I don't see how this will work considering the contraction of space-time right in front of the spaceship within this warp-bubble, will also in-turn cause a natural dilution of space-time right in front of the warp-bubble.

Even if that was not true, how will the warp-drive propagate the warp-bubble field itself faster than C to grab onto space-time in a timely manner?

It would seem to me this would cause the space-ship to feel that it's traveling faster than C, but to an outside observer it would only be traveling at C or less.

Warp drive may actually be possible, NASA scientist says

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