Interstellar Spaceflight

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Interstellar Spaceflight

Postby oldtrucker » May 7th, 2020, 7:44 am

Is size important for intelligence in creatures from other star systems?
I was working out ( cuz I'm weird and I think of dumb stuff to calculate) that if intelligent creatures that have a mass of a mouse, they would be able to do spaceflight using thousands of times less energy than a large mass creature like us.
A rocket for leaving the home planet and the habitat section for a crew of 100 would be no larger than our Saturn V rocket. Due to the starships low mass- less than 10 tons after the booster section is gone, getting it to 5% the speed of light could be feasible with a H3 fusion engine.

If the creatures were no larger than ants, then the ship could feasibly be accelerated to 20% the speed of light or faster by using home planet based laser propulsion or a combination of systems. I don't know how it would slow down when it got to its destination but that's not the point. If they were the size of ants, and if the starship was 2 meters long, it would be the size of a aircraft carrier or the Star Trek 'NCC- 1701 Enterpise' to us for relative size. Even if the ship was only 2 meters long and a mass of 100 kilos or less, getting it to 'relativistic speeds' where time dilation comes into play (> 90% speed of light) it would take a fuel tank of H3 the size of a shopping mall, and to get it to 99.99% the speed of light, it would take a H3 fuel tank the size of the moon. If 'they' were from Gliese 581 at 20 light years away, at 99.99% the speed of light it would take 3 months ship time. Something that's only 2 meters also has a better chance of not hitting anything like a pebble sized piece of rock. At 50% the speed of light, hitting a 1 gram rock would be like setting off a 3 kiloton nuclear bomb ( 13.8 trillion joules-hows that for muzzle energy?) on the surface of the ships hull. That wouldn't work out very well for a ship of any size.

I think one of the points that I'm making is that we are more likely to be visited by something very small than something our size due to physics n' fuel.
Would we even recognize their presence, or just swat them like a mosquito?
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Re: Interstellar Spaceflight

Postby Urban Cowboy » May 7th, 2020, 12:14 pm

I think some are already here, like the Japanese murder bees. :200:
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Re: Interstellar Spaceflight

Postby TylerM4 » May 8th, 2020, 11:25 am

Size of the ship isn't really a barrier for interstellar travel, rather it's the sheer distances.

Let's look at you example: Even at 5% speed of light, the nearest solar system is still 4.37 light years away resulting in a 1-way trip of 87.4 years.

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Re: Interstellar Spaceflight

Postby Jlabute » May 9th, 2020, 5:51 am

It’ll still be difficult to survive without gravity. Your body will wither away after a few years. So gotta take a big spinny-spaceship. As for brain-size, the bigger the brain, the bigger the appreciation for what you’re doing ;-)
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Re: Interstellar Spaceflight

Postby TylerM4 » May 9th, 2020, 7:59 am

Sadly, with the technology available today interstellar travel is mostly a pipe dream. Even if we were able to travel at the speed of light, travelling between solar systems is "impractical" IE 4.37 years 1-way to the closest system. 1000 years 1-way to the closest black hole. Travelling at anything higher than a small fraction of light speed is currently outside of our reach, yet to practically travel the stars we need to find a way to travel at multiple orders of light speed.

I say mostly, because I do think the idea of a very large multi-generational ship (in flight for 100+ years at a time) is within humanity's reach. BUT, it would easily represent the largest and most complex item that humanity has ever built. It would take decades to build, Trillions of dollars, and collaboration on a global scale. But I do think we could do it if we (by we I mean all of humanity) really wanted it.

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Re: Interstellar Spaceflight

Postby Jlabute » May 9th, 2020, 8:54 am

A pipe dream... or.... a wormhole dream. Tyler, I think you’re on to something! In fact, instead of making us go the speed of light, make light go the speed of us! That’ll fix its little red wagon. lol. Anyways, we don’t even have an idea of where to go yet. We think we can casually travel from point A to B to C and dozens of other places when in reality we cant even go from point A to point A.

I’m afraid nothing of the such will happen in my lifetime. A large multigenerational ship will take literally multi generations to build as well. It too will be a spinny thing, lol.
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Re: Interstellar Spaceflight

Postby oldtrucker » May 9th, 2020, 11:03 am

Jlabute wrote:It’ll still be difficult to survive without gravity. Your body will wither away after a few years. So gotta take a big spinny-spaceship. As for brain-size, the bigger the brain, the bigger the appreciation for what you’re doing ;-)


I think that if we had the tech to put together not a H3 fusion drive ( that would be low tech) , but a antimatter drive, then we would probably be able to find and manipulate gravitons, and create artificial gravity.
Antimatter....One drop of antiwater hitting water would result in about 10 kt of energy, so storing any real amount would require storing it on the far side of the moon for safety. What happens when the power goes out on the magnetic containment field storing a beer bottle sized amount of antimatter? The crater would be 3 miles across.
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Re: Interstellar Spaceflight

Postby oldtrucker » May 9th, 2020, 2:54 pm

TylerM4 wrote:Size of the ship isn't really a barrier for interstellar travel, rather it's the sheer distances.


Unless it's 'Breakthrough Starshot'. The plan is to launch multiple (1000 or so) very light weight space probes with small cameras and sensors- as in less than a few grams small, towards Proxima Cent. that would use deployed sails pushed by a very high power ground based laser. It would supposedly accelerate them to 20% C and hopefully at least a few would function when they got to their destination and fly through the system,sending back pics and info. 26 years later plus 4.3 years for the info to get back to Earth. Kind of a longshot.
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Re: Interstellar Spaceflight

Postby Jlabute » May 9th, 2020, 7:43 pm

oldtrucker wrote:
Jlabute wrote:It’ll still be difficult to survive without gravity. Your body will wither away after a few years. So gotta take a big spinny-spaceship. As for brain-size, the bigger the brain, the bigger the appreciation for what you’re doing ;-)


I think that if we had the tech to put together not a H3 fusion drive ( that would be low tech) , but a antimatter drive, then we would probably be able to find and manipulate gravitons, and create artificial gravity.
Antimatter....One drop of antiwater hitting water would result in about 10 kt of energy, so storing any real amount would require storing it on the far side of the moon for safety. What happens when the power goes out on the magnetic containment field storing a beer bottle sized amount of antimatter? The crater would be 3 miles across.


Although a step forward from where we are now, thrust from nuclear or chemical energy likely won’t do it IMO. Ion propulsion is in the same boat. Suggestions towards bending space I can only imagine would require enormous amounts of energy... more than what we can put in to space. I wonder what the most promising technology will be. We theorize about gravitons and the ability to control them, although we’ve never seen one nor understand what could control them. It’s been suggested they also travel at the speed of light ... although maybe an artificial gravitational environment can be made? We will need a compact means to do that in a specific area or pattern. Not in our lifetime I bet. We can generate gravitons already just by having mass, we can’t detect them though.
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Re: Interstellar Spaceflight

Postby Jlabute » May 10th, 2020, 5:15 pm

The fastest probe we’ve accomplished so far, aided by the suns gravitational pull, is 692,000 km/h. Pretty zippy at 192km/s which is 0.00064C.
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Re: Interstellar Spaceflight

Postby TylerM4 » May 11th, 2020, 8:38 am

oldtrucker wrote:
I think that if we had the tech to put together not a H3 fusion drive ( that would be low tech) , but a antimatter drive, then we would probably be able to find and manipulate gravitons, and create artificial gravity.
Antimatter....One drop of antiwater hitting water would result in about 10 kt of energy, so storing any real amount would require storing it on the far side of the moon for safety. What happens when the power goes out on the magnetic containment field storing a beer bottle sized amount of antimatter? The crater would be 3 miles across.


If we come up with a drive system powerful enough, we don't need artificial gravity.

Accelerate the ship at a constant 1G until the 1/2 way point, then spin 180* and decelerate at 1G for the last 1/2 of the trip. Even when constantly accelerating/decelerating at 1G It's still a very long trip tho :(
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Re: Interstellar Spaceflight

Postby oldtrucker » May 11th, 2020, 11:00 am

TylerM4 wrote:Accelerate the ship at a constant 1G until the 1/2 way point, then spin 180* and decelerate at 1G for the last 1/2 of the trip. Even when constantly accelerating/decelerating at 1G It's still a very long trip tho :(


I looked up a few websites for that and in general it appears it would take roughly 1 year at 1 g to reach 90%C- ish. When it gets to 99.999% I don't know if it even makes sense at 1 g because at those fine decimal points it's so close to C...yet so far. At 99.999%C at trip to a system 100 light years away takes 101 earth years. Just under 6 months (not including acceleration) ship time according to a online time dilation calculator. So for those last percentage points ,could something still accelerate at 1 g? Is it relative? No.That's a fiziks question that I think is beyond my math skills.
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Re: Interstellar Spaceflight

Postby TylerM4 » May 12th, 2020, 7:18 am

oldtrucker wrote: I looked up a few websites for that and in general it appears it would take roughly 1 year at 1 g to reach 90%C- ish. When it gets to 99.999% I don't know if it even makes sense at 1 g because at those fine decimal points it's so close to C...yet so far. At 99.999%C at trip to a system 100 light years away takes 101 earth years. Just under 6 months (not including acceleration) ship time according to a online time dilation calculator. So for those last percentage points ,could something still accelerate at 1 g? Is it relative? No.That's a fiziks question that I think is beyond my math skills.


Good point. You may want to maintain the acceleration past 90% just to maintain a false gravity. I guess it'll depend on the cost and availability of fuel for this hypothetical engine. As we approach C we run into relativistic effects that may prevent us from doing so then. The energy required to maintain 1g acceleration is on a logarithmic scale/relationship.
Kinetic Energy (KE) = 1/2 * Mass * speed squared KE=0.5mv^2
It's the Speed squared (v^2) that results in the logarithmic relationship between energy and speed. It's also the reason why it takes 4x longer to stop your car when you double your speed.

As speed increases, the energy required to maintain that same acceleration increases at the square of speed. So long story short - an engine that can maintain 1g of acceleration while travelling at 0.9C would need to output a tremendous amount of energy. Energy that we cannot even fathom - in the case of a large spaceship we're talking about "comparable to total output of a star" levels of energy. An engine powerful enough to supply all of the electricity used on earth wouldn't even come close to being powerful enough. You get the idea...
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Re: Interstellar Spaceflight

Postby Bsuds » May 12th, 2020, 7:26 am

Don't forget you have to slow down as well so you can only accelerate half way then you need to turn around and decelerate.
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Re: Interstellar Spaceflight

Postby JagXKR » May 12th, 2020, 10:43 am

He didn't forget. Check a few posts up.

The whole idea of interstellar flight occurring before any human currently alive passes on is ridiculous.
There is NO realistic way to get to neighboring stars with current understanding of physics AND engineering. Just a lot of science fiction with no real world solutions for solving major engineering roadblocks.

I may live long enough to see the first humans attempt a trip to Mars. I hope to still have my cognitive ability to even notice that it's happening. Until then I revel in the current missions and soon to be launched missions of robotic and human spaceflight.
Perseverance (with Ingenuity) , Parker, Europa Clipper etc.

Also the money required is beyond anything we can imagine. Even the Europa Clipper just had a cut to a key instrument due to cost. Replaced with a cheaper, less detailed instrument. Science community is a bit miffed to say the least.

Dream all you want but it is just that.
Why use a big word when a diminutive one will suffice.

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