Interstellar travel
Discussion
glazbagun said:
Skeptisk said:
Whoozit said:
Mr Whippy said:
It’s still a bit 2D trying to understand 3D here isn’t it?
I suppose we need aliens that are very advanced but are constrained by lots of physical things that we find ourselves constrained by.
[snip]
I think we’re pretty much going to be alone until we evolve to not see the universe the way we do.
And when we can see it all for what it truly is, we will realise we don’t need to travel around it in machines… we’ll just travel around it in our minds… peeking in at stuff from our extra dimensions of perspective.
Ah well yes. God mode. Somewhat of a cheat code answer to this thread, don't you think I suppose we need aliens that are very advanced but are constrained by lots of physical things that we find ourselves constrained by.
[snip]
I think we’re pretty much going to be alone until we evolve to not see the universe the way we do.
And when we can see it all for what it truly is, we will realise we don’t need to travel around it in machines… we’ll just travel around it in our minds… peeking in at stuff from our extra dimensions of perspective.
Talk or warp drives and folding space seem to me not much different than saying you will invent magic and then create a spell to teleport yourself anywhere in the universe.
Before the enlightenment and the development of science lots of people believed in magic and so there was magic - surely not all the witches burnt were innocent!
To allow us to use magic to get to the stars we just need to make people believe again. I’m sure my grant application of £10 million to get people to believe is cheap compared to NASA…
deckster said:
Mr Whippy said:
WrekinCrew said:
It doesn't matter how high you get, you need velocity to go anywhere, hence "escape velocity", 7 miles/second.
So there is no advantage to being high to get out of the bulk of the atmosphere for both inward and outward journeys, at any scale of operations?May as well still just use a rocket from sea level?
Or would it obviate the need for using a 1st stage?
Mr Whippy said:
So a 150,000ft hill with a 10,000km/h maglev on it, aiming up at say 10 degrees from the horizontal, would be useless?
Yes. Because 10,000km/h is way under escape velocity - the fact that it's being launched from the top of a hill is entirely irrelevant.Get that baby to 50,000km/h however and we're in business. There are of course just couple of teeny tiny engineering challenges with your suggestion that mean that it is way, way easier to just light a big rocket under the payload.
Eric Mc said:
Precisely.You can climb half way to the moon but if you haven't given yourself enough velocity, you'll fall all the way back to earth.
That's exactly what happened to some of the earliest attempts to send probes to the moon.
It's a major theme in Jules Verne's 'From the Earth to the Moon'. It has a surprising amount of physics in it.That's exactly what happened to some of the earliest attempts to send probes to the moon.
Alias218 said:
With our current understanding of physics, interstellar travel in any practical sense is simply not possible. Unless we discover some hitherto unknown physical phenomena, we are stuck looking at the universe through telescopes.
And even if we could reach a significant fraction of lightspeed, lets say 1%, it would still take us 450 years to each the nearest extra-solar star if we gunned it and whizzed on by. Bear in mind that the Solar Parker Probe reached 0.054% the speed of light.
As I have mentioned in another thread on this sub, would it even be worth it when after n years we have a craft that does (hypothetically) more than twice the speed of the one already on its way? The first craft will be overtaken by the second. And the second potentially by the third after another n+x years.
Not to mention the effect that extended space travel in zero, or perhaps low, gravity would have on the human body, even if in sci-fi-esque stasis. Perhaps we send a generation ship (which would take twice as long as a fly-by as the ship would be accelerating half the time, and then decelerating the other half). The ship arrives, and then what? There's nothing in the Alpha Centauri system except maybe a planet that may have some habitable qualities, but probably not. They send their data back, and the response from Earth is, "great, thanks but we know this already from Earth based observations because our technology is now 900 years more advanced than when you left, and by the way a probe reached the Alpha Centauri system 600 years ago." That's even if the passengers are A. still alive, and B. the slightest bit interested in completing a mission their forebears started nearly a millennia ago.
And that's just for our closest neighbour!
As I say, unless there is some gap in our scientific knowledge that allows covering vast distances in human time-frames then we're stuck in the solar system (or we transfer our consciousnesses to non-biological hosts and become essentially immortal).
I'm currently playing Starfield, a post-Earth exploration/shooting/RPG space game. Lots of fun and real-ish physics. And even if we could reach a significant fraction of lightspeed, lets say 1%, it would still take us 450 years to each the nearest extra-solar star if we gunned it and whizzed on by. Bear in mind that the Solar Parker Probe reached 0.054% the speed of light.
As I have mentioned in another thread on this sub, would it even be worth it when after n years we have a craft that does (hypothetically) more than twice the speed of the one already on its way? The first craft will be overtaken by the second. And the second potentially by the third after another n+x years.
Not to mention the effect that extended space travel in zero, or perhaps low, gravity would have on the human body, even if in sci-fi-esque stasis. Perhaps we send a generation ship (which would take twice as long as a fly-by as the ship would be accelerating half the time, and then decelerating the other half). The ship arrives, and then what? There's nothing in the Alpha Centauri system except maybe a planet that may have some habitable qualities, but probably not. They send their data back, and the response from Earth is, "great, thanks but we know this already from Earth based observations because our technology is now 900 years more advanced than when you left, and by the way a probe reached the Alpha Centauri system 600 years ago." That's even if the passengers are A. still alive, and B. the slightest bit interested in completing a mission their forebears started nearly a millennia ago.
And that's just for our closest neighbour!
As I say, unless there is some gap in our scientific knowledge that allows covering vast distances in human time-frames then we're stuck in the solar system (or we transfer our consciousnesses to non-biological hosts and become essentially immortal).
One of the storylines is a generation ship which arrives at a promising planet, only to find humanity leapfrogged them and there's a luxury resort there. Your job is to upgrade the generation ship with magic interstellar drives and persuade the captain to go somewhere else.
Simpo Two said:
It's a major theme in Jules Verne's 'From the Earth to the Moon'. It has a surprising amount of physics in it.
Which he didn't get right in some area. He misunderstood how Zero G (microgravity) worked, for instance. He also conveniently ignored the crushing G forces that would have been experienced by the occupants of a spacecraft fired from a cannon.LunarOne said:
It doesn't work. Try throwing a ball in a straight line while you're spinning. And the effects on the inner ear which allow you to feel a sense of balance get messed up and you will start feeling motion sickness pretty quickly due to coriolis forces.
A ball will always travel in a straight line after being thrown.julian64 said:
LunarOne said:
It doesn't work. Try throwing a ball in a straight line while you're spinning. And the effects on the inner ear which allow you to feel a sense of balance get messed up and you will start feeling motion sickness pretty quickly due to coriolis forces.
A ball will always travel in a straight line after being thrown.https://www.youtube.com/watch?v=kPB8f8wO6eo&t=... Coriolis force in two dimensions
https://www.youtube.com/watch?v=ryrGPjyKhO4 simulating 3D of coriolis + centrifugal force in a rotating ring, from The Expanse.
Eric Mc said:
Simpo Two said:
It's a major theme in Jules Verne's 'From the Earth to the Moon'. It has a surprising amount of physics in it.
Which he didn't get right in some area. He misunderstood how Zero G (microgravity) worked, for instance. He also conveniently ignored the crushing G forces that would have been experienced by the occupants of a spacecraft fired from a cannon.Eric Mc said:
Unless affected by a gravity field in which case it will follow a curve. In fact, genuine straight line trajectories are rare.
And of course, if you're David Beckham (or Rivelinho if you are old enough to remember him).
I think that under general relativity the ball is following a straight line (geodesic?) and it is us who are following a curve as the surface of the earth is accelerating us from the path we would travel in spacetime.And of course, if you're David Beckham (or Rivelinho if you are old enough to remember him).
deckster said:
Mr Whippy said:
So a 150,000ft hill with a 10,000km/h maglev on it, aiming up at say 10 degrees from the horizontal, would be useless?
Yes. Because 10,000km/h is way under escape velocity - the fact that it's being launched from the top of a hill is entirely irrelevant.Get that baby to 50,000km/h however and we're in business. There are of course just couple of teeny tiny engineering challenges with your suggestion that mean that it is way, way easier to just light a big rocket under the payload.
But yeah, generally a big rocket is easier in engineering terms, however Spinlaunch have an interesting concept
RizzoTheRat said:
But 150,000ft (45km) puts you out of most of the atmosphere, so very little drag, and you're about 1/3 of the way to low earth orbit velocity (about 28,000kph), so you've saved a lot of dV already, and more importantly a lot of mass, so you're rocket can be way smaller. This is pretty much the idea behind Pegasus, Virgin One and other air launched systems.
But yeah, generally a big rocket is easier in engineering terms, however Spinlaunch have an interesting concept
But we're talking interstellar, so you also have to exceed the solar system escape velocity - 42km/s or 151,000 kph.But yeah, generally a big rocket is easier in engineering terms, however Spinlaunch have an interesting concept
RizzoTheRat said:
But 150,000ft (45km) puts you out of most of the atmosphere, so very little drag, and you're about 1/3 of the way to low earth orbit velocity (about 28,000kph), so you've saved a lot of dV already, and more importantly a lot of mass, so you're rocket can be way smaller. This is pretty much the idea behind Pegasus, Virgin One and other air launched systems.
But yeah, generally a big rocket is easier in engineering terms, however Spinlaunch have an interesting concept
How many Pegasus launches are there these days? And look what happened to Virgin Orbital.But yeah, generally a big rocket is easier in engineering terms, however Spinlaunch have an interesting concept
Making it work practically and commercially is very difficult.
WrekinCrew said:
But we're talking interstellar, so you also have to exceed the solar system escape velocity - 42km/s or 151,000 kph.
But due to the tyranny of the rocket equation, the more weight you can shave off at the start the better, the more fuel you have, the more fuel you need to be able to carry it.At launch you have 2 main losses, Gravity (upward thrust being negated by gravity) and Drag. Starting higher up means you can massively reduce both of those.
Eric Mc said:
How many Pegasus launches are there these days? And look what happened to Virgin Orbital.
Making it work practically and commercially is very difficult.
Hence as I said, rockets are easier at the moment. the real game changer will be if someone ever figures out how to make a space elevator.Making it work practically and commercially is very difficult.
So - never.
(Or at least, not for a very, very long time).
Regarding escaping the solar system - we already have a few craft which are doing this, Pioneers 10 and 11, Voyagers 1 and 2, New Horizons etc.
However, they are relatively small machines and much less massive than anything capable of carrying humans.
(Or at least, not for a very, very long time).
Regarding escaping the solar system - we already have a few craft which are doing this, Pioneers 10 and 11, Voyagers 1 and 2, New Horizons etc.
However, they are relatively small machines and much less massive than anything capable of carrying humans.
Whoozit said:
Why do you think the reporting on the deep space telescope discoveries often say something like "peering into the birth of the Universe"? For exactly the same reason. It's taken untold billions of years for the light from that event to reach our planet.
Gonna reveal my utter ignorance of physics here, and I know it's a bit off topic, but as you mentioned it...I always wonder how it is that the matter our planet is made up of got to this point of space, before all that light from the birth of the Universe? Given that nothing can travel faster than light, wouldn't all that light have passed by here long before the matter arrived which would form our planet? No doubt there's an explanation, and no doubt I won't understand it, but I hope you get the premise of my question?
Yeah I can't see a space elevator happing in the next few centuries.
Given that SpaceX's current plans would need something like 9 Starship launches to get enough fuel in to orbit to get one of them to Mars with a 150 tonne (?) payload, getting anything much bigger than a small probe out of the solar system would take some significant effort, even with solar sails, I'm guessing you'd need to shove in out in to a very high orbit, or better yet a solar orbit, using conventional rockets.
Given that SpaceX's current plans would need something like 9 Starship launches to get enough fuel in to orbit to get one of them to Mars with a 150 tonne (?) payload, getting anything much bigger than a small probe out of the solar system would take some significant effort, even with solar sails, I'm guessing you'd need to shove in out in to a very high orbit, or better yet a solar orbit, using conventional rockets.
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