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Relativistic Spaceship

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Re: Relativistic Spaceship

#411

Post by adrianN »

kypro wrote: post #402
TheOtherHobbes wrote: post #374

Earlier quoted context omitted.

It's clearly not a solvable problem with current ideas about technology. No amount of ice, rock, magnetism, or Magic Unobtanium is going to make this practical. I'm not even sure about warp drives. Bending spacetime one way means it has to squish back the other way. The energy released might not affect the ship - possibly - but I'd be surprised if it didn't affect the spacetime it had just passed through. Some kind o…

Am I wrong to think it seems probable that such things aren't realistically possible given the fact that the universe seems to be so lifeless? If the practical limits of rocket technology don't allow life to much beyond their own solar system then given the vastness of space that would be a good reason why we don't see any evidence of intergalactic civilisations or large feats of engineering. All other explanations f…

Sending humans across thousands of light years seems almost impossible , but sending von Neumann probes throughout the galaxy should be possible with some reasonable improvement to our technology.

Re: Relativistic Spaceship

#412

Post by greggsy »

heads wrote: post #313
MilStdJunkie wrote: post #26

Earlier quoted context omitted.

Every proton would have the energy of a baseball. It's bananas. Granted, space is really empty, but it's not that empty, somewhere around a hundred atoms per cubic meter. Your ship might look like a very, very long shooting star. Probably dialing the speed down a touch would be worth it for whatever your shielding material is, but who knows? We're talking miracle engines here. I think in the "Valkyrie" ship-on-a-stri…

If you’re doing 2e8 m/s, your ship is long and thin with a 1m3 nose cone, and space has 100 baseballs per m3 then you’re being hit by 2e10 baseballs a second. How do I get an idea for what 20 billion baseballs (2TJ) feels like? Apparently bullets are about an order of magnitude more energetic than baseballs (800J vs 80J) so I guess I could try to build my intuition based on being shot ~2 billion times a second instea…

Could you repeatedly send disposable ‘dozer’ drone ships towards your destination to help clear the way, and potentially devise a means of keeping the clearing free of stray atoms?

Re: Relativistic Spaceship

#413

Post by the_third_wave »

ithkuil wrote: post #173
JumpCrisscross wrote: post #160

Earlier quoted context omitted.

> always face the exhaust in that direction! It's not rocket science! You don't see a problem with trying to accelerate with two exhaust streams at 180º to each other?

What if the front one is only a small fraction of the thrust at the rear? Would that be enough to "clear the path". Surely it would cost some efficiency but it may beat he alternative

In other words the space-equivalent of a supercavitating torpedo like the Shkval [1], more or less an underwater rocket which creates its own gas bubble around the projectile by deflecting part of the exhaust stream to nozzles on the front of the device.

[1] https://en.wikipedia.org/wiki/VA-111_Shkval

Re: Relativistic Spaceship

#414

Post by meindnoch »

denton-scratch wrote: post #360
MilStdJunkie wrote: post #26

Earlier quoted context omitted.

Every proton would have the energy of a baseball. It's bananas. Granted, space is really empty, but it's not that empty, somewhere around a hundred atoms per cubic meter. Your ship might look like a very, very long shooting star. Probably dialing the speed down a touch would be worth it for whatever your shielding material is, but who knows? We're talking miracle engines here. I think in the "Valkyrie" ship-on-a-stri…

> somewhere around a hundred atoms per cubic meter. Wikipedia says that intergalactic space contains less than one hydrogen atom per cubic meter; and that most of the baryonic matter in intergalactic space consists of hydrogen and helium atoms. If I've understood it correctly... https://en.wikipedia.org/wiki/Outer_space

intergalactic != interstellar

Re: Relativistic Spaceship

#415

Post by htk »

jcul wrote: post #86
robertlagrant wrote: post #43

Earlier quoted context omitted.

I like that old Arthur C Clarke novel, The Songs of Distant Earth[0], where they travel with an ablative shield in front made of ice, and they can make new shield segments by finding planets with water. [0] https://en.wikipedia.org/wiki/The_Songs_of_Distant_Earth

I read project hail Mary over Christmas, and they deal with this problem too. Though I can't say much without giving away spoilers. A great read if you are a sci-fi fan!

Thank you for the recommendation! Started reading yesterday and I'm loving it.

Re: Relativistic Spaceship

#416

Post by [deleted] »

eru wrote: post #203
LoganDark wrote: post #128

Earlier quoted context omitted.

Yes because ions are... ions. You don't see photons knocking the planet out of orbit, do you? They can exert force but they don't exert that much force. But if you're trying to avoid self-propulsion and want to launch from Earth, say, even a 200kg craft, anywhere "close to the speed of light", then that will most probably require a significant enough amount of force to knock the planet out of orbit.

No, what makes you think so? If you can apply small force over a long time, that will get you up to speed, too. Someone did the math in the thread, and suggested that a constant 1g of acceleration would get you to the centre of the galaxy in 20 years (as measured by the clocks traveling on your spaceships). 1g of acceleration for 200kg is about 1962 Newton. (This back of the envelope calculation assumes you have eg s…

[deleted]

Re: Relativistic Spaceship

#417

Post by LoganDark »

eru wrote: post #203
LoganDark wrote: post #128

Earlier quoted context omitted.

Yes because ions are... ions. You don't see photons knocking the planet out of orbit, do you? They can exert force but they don't exert that much force. But if you're trying to avoid self-propulsion and want to launch from Earth, say, even a 200kg craft, anywhere "close to the speed of light", then that will most probably require a significant enough amount of force to knock the planet out of orbit.

No, what makes you think so? If you can apply small force over a long time, that will get you up to speed, too. Someone did the math in the thread, and suggested that a constant 1g of acceleration would get you to the centre of the galaxy in 20 years (as measured by the clocks traveling on your spaceships). 1g of acceleration for 200kg is about 1962 Newton. (This back of the envelope calculation assumes you have eg s…

I think everyone is collectively ignoring that I'm specifically talking about accelerating the craft from earth, not using an ion drive or similar form of propulsion on-board. As that's what is implied by the comment that I responded to: "If you could shoot it out at close to speed of light"

Re: Relativistic Spaceship

#418

Post by mmmmmbop »

username923409 wrote: post #290

I had fun with setting the "throttle_value" variable to something insane, like 30 (1 is the max on the slider), to see how close to c you need to travel at for the web app itself to disintegrate. Apparently, it takes just over two lines of "9"s on a 1920px display for this to happen. The speed wraps back around to zero, and the world time becomes NaN as an added bonus for (nearly) breaking the laws of physics.

> just over two lines of "9"s on a 1920px display

I love this unit of measurement.

Re: Relativistic Spaceship

#419

Post by camelliahmmm »

ryandrake wrote: post #12

Great visualization of the unintuitive nature of special relativity. It's kind of mind blowing to realize that if we could accelerate our spaceship at a mere 1G continuously, we could visit the center of the Milky Way in under 20 years (spaceship time), totally do-able in a human lifespan. Of course 27900 years would have passed on Earth, so you wouldn't be able to tell anyone about your vacation.

[dead]

Re: Relativistic Spaceship

#420

Post by denton-scratch »

meindnoch wrote: post #414
denton-scratch wrote: post #360

Earlier quoted context omitted.

> somewhere around a hundred atoms per cubic meter. Wikipedia says that intergalactic space contains less than one hydrogen atom per cubic meter; and that most of the baryonic matter in intergalactic space consists of hydrogen and helium atoms. If I've understood it correctly... https://en.wikipedia.org/wiki/Outer_space

intergalactic != interstellar

Well, I don't think the discussion was restricted to interstellar space; for example there's been quite a bit of chat about how long it would take, at 1G (on the astronaut's watch) to reach the edge of the (known) universe.
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