> -over a ton of anti-matter would be required to get a ton of payload to a nearby star at ~40% the speed of light
It all sounds awful until you get to this line. What are the equivalent numbers for fusion? All else being equal, 250 tons of fuel per 1 ton payload? And that payload has to include the reactor and storage and shielding and everything.
Probably only space based antimatter production makes sense, the risk of blowing up the most expensive and dangerous stuff on Earth is just too big. Fusion sounds like a clear winner as opposed to antimatter.
I assume any future antimatter based propulsion would rely on some sort of metastable particle pair that are made up of matter-antimatter components like protons, except one that can be more easily/efficiently split and recombined. Otherwise the factories will just blow up the first time there's a serious accident or containment failure.
Just as an example: imagine particle A made up of up, bottom, and strange quark and particle B made up of down, charm, and top quarks (I'm ignoring charge) that can be stored without interacting. The engine splits them into quarks that then can annihilate each other (AFAIK that's not how quark plasmas work but you get my drift).
I think hydrogen can be simply found in space, along the way. Not sure about the concentration of deuterium and tritium. I suspect once you get to 1% of c, you can find enough.
If you need to lift all the fuel from Earth, sure, antimatter all the way. Although, they already suggest making it in space for some reasons.
> I think hydrogen can be simply found in space, along the way. Not sure about the concentration of deuterium and tritium. I suspect once you get to 1% of c, you can find enough.
That's called a Bussard ramjet. Long story short:
> A 2021 study found that, while feasible in principle, the practical construction of a useful Bussard ramjet would be beyond even a civilization of Kardashev type II. [1]
Yes, but hydrogen is cheap. Especially compared to anti-matter.
Shielding is also going to be a huge issue for anti-matter drives (even without a human crew). Anyone know how the energy of EM radiation emitted from a fusion reaction compares to that emitted from an matter:anti-matter reaction?
The only way to go is to go is slowly and by not sending a ton, ie inject genetic material into a rock that's already on its way, hope for the one in a trillion chance that it takes root somewhere. That we're so alone in the galaxy is proof of this.
I don't think there is any real advantage of matching velocity with a rock and transferring material to it, compared to sending your own spacecraft at that velocity.
A big rock with its own momentum is more likely to come down on the surface (wherever it is) intact enough. But yeah there may be other ways to spread our seed. My point is that it will unpropelled for most of the journey, and a seed not an ape.
Comments
> -over a ton of anti-matter would be required to get a ton of payload to a nearby star at ~40% the speed of light
It all sounds awful until you get to this line. What are the equivalent numbers for fusion? All else being equal, 250 tons of fuel per 1 ton payload? And that payload has to include the reactor and storage and shielding and everything.
Fun fact, the technology needed to accelerate a spacecraft to 10% of the speed of light already existed in the 60s:
https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
Probably only space based antimatter production makes sense, the risk of blowing up the most expensive and dangerous stuff on Earth is just too big. Fusion sounds like a clear winner as opposed to antimatter.
I've found direct fusion drive as a concept a company is working on: https://en.wikipedia.org/wiki/Direct_Fusion_Drive
I assume any future antimatter based propulsion would rely on some sort of metastable particle pair that are made up of matter-antimatter components like protons, except one that can be more easily/efficiently split and recombined. Otherwise the factories will just blow up the first time there's a serious accident or containment failure.
Just as an example: imagine particle A made up of up, bottom, and strange quark and particle B made up of down, charm, and top quarks (I'm ignoring charge) that can be stored without interacting. The engine splits them into quarks that then can annihilate each other (AFAIK that's not how quark plasmas work but you get my drift).
And definitely not too close to Earth. Maybe a Lagrange point.
I think hydrogen can be simply found in space, along the way. Not sure about the concentration of deuterium and tritium. I suspect once you get to 1% of c, you can find enough.
If you need to lift all the fuel from Earth, sure, antimatter all the way. Although, they already suggest making it in space for some reasons.
> I think hydrogen can be simply found in space, along the way. Not sure about the concentration of deuterium and tritium. I suspect once you get to 1% of c, you can find enough.
That's called a Bussard ramjet. Long story short:
> A 2021 study found that, while feasible in principle, the practical construction of a useful Bussard ramjet would be beyond even a civilization of Kardashev type II. [1]
[1] https://en.wikipedia.org/wiki/Bussard_ramjet
Yes, but hydrogen is cheap. Especially compared to anti-matter.
Shielding is also going to be a huge issue for anti-matter drives (even without a human crew). Anyone know how the energy of EM radiation emitted from a fusion reaction compares to that emitted from an matter:anti-matter reaction?
The only way to go is to go is slowly and by not sending a ton, ie inject genetic material into a rock that's already on its way, hope for the one in a trillion chance that it takes root somewhere. That we're so alone in the galaxy is proof of this.
I don't think there is any real advantage of matching velocity with a rock and transferring material to it, compared to sending your own spacecraft at that velocity.
A big rock with its own momentum is more likely to come down on the surface (wherever it is) intact enough. But yeah there may be other ways to spread our seed. My point is that it will unpropelled for most of the journey, and a seed not an ape.