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?
Warp drive may actually be possible, NASA scientist says
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Re: Warp drive may actually be possible, NASA scientist says
#12Can 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?
Re: Warp drive may actually be possible, NASA scientist says
#13Can 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?
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.
Re: Warp drive may actually be possible, NASA scientist says
#14The article doesn't mention exotic matter. Did they find a way to build an engine without exotic matter?
Re: Warp drive may actually be possible, NASA scientist says
#15Can 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?
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 t…
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.
Re: Warp drive may actually be possible, NASA scientist says
#16> "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...
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…
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.
Re: Warp drive may actually be possible, NASA scientist says
#17Earlier quoted context omitted.
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…
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.
It's not that simple. You are vastly underestimating how much scaleup is required to sustain that acceleration up until you get a reasonable trip time.
Here's the summary from NASA:
"Here are four examples [large graphic][1] of what it would take to send a canister about the size of a Shuttle payload (or a school bus) past our nearest neighboring star...and allowing 900 years for it to make this journey.
Well....If you use chemical engines like those that are on the Shuttle, well..., sorry, there isn’t enough mass in the universe to supply the rocket propellant you’d need.
So let’s step up to next possibilities, nuclear rockets with a predicted performance that’s 10 to 20 times better!
Well...it’s still not looking all that good. For a fission rocket you would need a BILLION SUPERTANKER size propellant tanks to get you there, and even with fusion rockets you would still need a THOUSAND SUPERTANKERS!
Even if we look at the best conceivable performance that we could engineer based on today’s knowledge, say an Ion engine or an antimatter rocket whose performance was 100 times better that the shuttle engines, we would need about ten railway tanker sized propellant tanks.
That doesn’t sound too bad, until you consider that we didn’t bring along any propellant to let us stop when we get to the other star system...or if we want to get there quicker than 9 centuries.
Once you add the desire to actually stop at your destination, or if you want to get there sooner, you’re back at the incredible supertanker situation again, even for our best conceivable rockets.
In conclusion, we’d really like to have a form of propulsion that doesn’t need any propellant! This implies the need to find some way to modify gravitational or inertial forces or to find some means to push against the very structure of spacetime itself."
The rest of the website[2] has some good information, even if the organization is a bit disjoint.
[1]: http://www.nasa.gov/centers/glenn/images/content/84509main_w...
[2]: http://www.nasa.gov/centers/glenn/technology/warp/ipspaper.h...
Re: Warp drive may actually be possible, NASA scientist says
#18Earlier quoted context omitted.
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 t…
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 an…
Honestly? I'm not sure. I know there are at least a few physicists who post on HN, and perhaps one of them could provide a more informed estimation than I.
Bear in mind, this article only addresses one of the many fundamental challenges to the Alcubierre drive: the energy requirements. Typically, the energy requirement has been considered the primary challenge to the feasibility of the device. But it's not the only one. Science hasn't completely worked out what would happen inside the bubble, or what happens to particles of matter interacting with the bubble at its leading edge. I've heard at least one speculation that the bubble would fill up with Hawking radiation and pretty much roast everyone alive inside it, like a big, interstellar dutch oven.
Another issue is the stability of the bubble itself. Again, the article doesn't really address this issue. But it's a pretty big one.
Re: Warp drive may actually be possible, NASA scientist says
#19One 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 tw…
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…
"In fact it is possible" is a pretty strong way to talk about moving something that might not exist.
Re: Warp drive may actually be possible, NASA scientist says
#20I 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.