3 ms·

Can we really accelerate any probe to faster than 1% c? Or 2% c?

by avmich 4mo ago

r2_pilot 4mo ago
Yes, with lasers or nuclear energy
patagurbon 4mo ago
We have the physics but not the engineering. See the Breakthrough Starshot project for instance
altruios 4mo ago
One idea that stuck out to me was an array of giant thin solar powered spinning metal Crookes radiometers magnets in a line to make a railgun-like launcher. Materially cheap to do. Related, but not exactly what I was thinking of: https://www.centauri-dreams.org/2025/08/05/a-rotating-probe-launcher-alternative-to-tars/ https://www.centauri-dreams.org/2025/08/05/a-rotating-probe-... The original source I'm thinking of may be lost to time :( I'll keep hunting. edit:found! https://www.youtube.com/watch?v=MDM1COWJ2Hc https://www.youtube.com/watch?v=MDM1COWJ2Hc
tclancy 4mo ago
Per new Space Force regulations, we are using F for an adjusted speed of light. We are currently able to achieve 1.48F.
kimixa 4mo ago
No, not even close. The issue is simply exhaust velocity and reaction mass, that leads us into the tyranny of the rocket equation - in that you have to carry that reaction mass with you and accelerate that mass too. Even if you had magic infinite energy - e.g. it's supplied externally by a laser or similar. Using the theorized maximum of 31km/s exhaust velocity of project orion (much higher than any current high impulse propulsion technologies) you'd need to have thrown out something similar to 10^42 times the probe's mass out the back at that 31km/s velocity. That means to accelerate a 1kg probe to 1%c you'd need to start with a spacecraft holding a reaction mass equivalent to a few trillion suns worth of mass. Hardly seems worth it. It's all about exhaust velocity - increase that and it scales down quickly. Using the theoretical max of 500km/s of VASIMIR for example means it's only 400x the mass of the probe of reaction mass - but that's still theory and max thrust limits means it'll take the order of millions of years to reach that sort of speed.
- zer00eyz 4mo ago
  > No, not even close. 10% of C is theoretically possible with a space sail, and lasers. Will it work? Well we don't know cause we haven't tried.
  - kimixa 4mo ago
    Space sails are super low thrust though, even lower than my VASIMIR example - so will take even longer to reach the desired speed - though they have the advantage of not having to carry the complex and heavy engine I ignored that in the rough estimates anyway. So by the time they're theoretically close to the desired speed they'll be on the other side of the galaxy at least, even if it took millions of years to get there at the much slower average speed.
    - tatjam 4mo ago
      You can't use a solar sail for this, but if you use lasers, you can get a few newtons / GW of incident laser power. Sci-fi stuff but if you can make a very very light reflector that can somehow be cooled (microscopic IR dipoles come to mind), and a very very focused and powerful laser, you can go a long way. Not sure what the purpose of moving a thin metalized foil at a fraction of lightspeed would be, though :)
      - kimixa 4mo ago
        Yeah, many of the theoretical solar sail ideas fall down on what I consider a useful "probe" is, and what it can mass. As mentioned in my other comment, if you define the "probe" to be "a single particle" we /already/ do this all the time in particle accelerators. But it's clearly not a useful "probe" I believe the original thought experiment implied. A few hundred grams of super thin solar sail material is still very much in the "Not A Probe" definition in my mind. Plus even the best laser dispersion quickly gets significant at the distances required to give the sail the time to accelerate at such a low thrust.
      - floxy 4mo ago
        Roundtrip Interstellar Travel Using Laser-Pushed Lightsails https://ia800108.us.archive.org/view_archive.php?archive=/24/items/wikipedia-scholarly-sources-corpus/10.2514.zip&file=10.2514%252F3.8632.pdf https://ia800108.us.archive.org/view_archive.php?archive=/24...
ck2 4mo ago
I think the idea is tic-tac sized probes with nano circuitry (that doesn't exist yet) accelerated by lasers so they don't have to carry the power source Obviously stopping is the problem, they can never stop but at some point no need
- IAmBroom 4mo ago
  Before someone mentions IBM's (completely BS) "sub-nanometer circuitry": it isn't nearly sub-nm, except if you look at it from one particular way. The real estate is still many nanometers in dimension. The gates aren't even sub-nano; gate-to-gate interactions are, kind of.

Can we really accelerate any probe to faster than 1% c? Or 2% c?

by avmich 4mo ago

Can we really accelerate any probe to faster than 1% c? Or 2% c?

r2_pilot 4mo ago

Yes, with lasers or nuclear energy

patagurbon 4mo ago

We have the physics but not the engineering. See the Breakthrough Starshot project for instance

altruios 4mo ago

One idea that stuck out to me was an array of giant thin solar powered spinning metal Crookes radiometers magnets in a line to make a railgun-like launcher. Materially cheap to do. Related, but not exactly what I was thinking of: https://www.centauri-dreams.org/2025/08/05/a-rotating-probe-launcher-alternative-to-tars/ https://www.centauri-dreams.org/2025/08/05/a-rotating-probe-... The original source I'm thinking of may be lost to time :( I'll keep hunting. edit:found! https://www.youtube.com/watch?v=MDM1COWJ2Hc https://www.youtube.com/watch?v=MDM1COWJ2Hc

tclancy 4mo ago

Per new Space Force regulations, we are using F for an adjusted speed of light. We are currently able to achieve 1.48F.

kimixa 4mo ago

No, not even close. The issue is simply exhaust velocity and reaction mass, that leads us into the tyranny of the rocket equation - in that you have to carry that reaction mass with you and accelerate that mass too. Even if you had magic infinite energy - e.g. it's supplied externally by a laser or similar. Using the theorized maximum of 31km/s exhaust velocity of project orion (much higher than any current high impulse propulsion technologies) you'd need to have thrown out something similar to 10^42 times the probe's mass out the back at that 31km/s velocity. That means to accelerate a 1kg probe to 1%c you'd need to start with a spacecraft holding a reaction mass equivalent to a few trillion suns worth of mass. Hardly seems worth it. It's all about exhaust velocity - increase that and it scales down quickly. Using the theoretical max of 500km/s of VASIMIR for example means it's only 400x the mass of the probe of reaction mass - but that's still theory and max thrust limits means it'll take the order of millions of years to reach that sort of speed.

zer00eyz 4mo ago
> No, not even close. 10% of C is theoretically possible with a space sail, and lasers. Will it work? Well we don't know cause we haven't tried.
- kimixa 4mo ago
  Space sails are super low thrust though, even lower than my VASIMIR example - so will take even longer to reach the desired speed - though they have the advantage of not having to carry the complex and heavy engine I ignored that in the rough estimates anyway. So by the time they're theoretically close to the desired speed they'll be on the other side of the galaxy at least, even if it took millions of years to get there at the much slower average speed.
  - tatjam 4mo ago
    You can't use a solar sail for this, but if you use lasers, you can get a few newtons / GW of incident laser power. Sci-fi stuff but if you can make a very very light reflector that can somehow be cooled (microscopic IR dipoles come to mind), and a very very focused and powerful laser, you can go a long way. Not sure what the purpose of moving a thin metalized foil at a fraction of lightspeed would be, though :)
    - kimixa 4mo ago
      Yeah, many of the theoretical solar sail ideas fall down on what I consider a useful "probe" is, and what it can mass. As mentioned in my other comment, if you define the "probe" to be "a single particle" we /already/ do this all the time in particle accelerators. But it's clearly not a useful "probe" I believe the original thought experiment implied. A few hundred grams of super thin solar sail material is still very much in the "Not A Probe" definition in my mind. Plus even the best laser dispersion quickly gets significant at the distances required to give the sail the time to accelerate at such a low thrust.
    - floxy 4mo ago
      Roundtrip Interstellar Travel Using Laser-Pushed Lightsails https://ia800108.us.archive.org/view_archive.php?archive=/24/items/wikipedia-scholarly-sources-corpus/10.2514.zip&file=10.2514%252F3.8632.pdf https://ia800108.us.archive.org/view_archive.php?archive=/24...

ck2 4mo ago

I think the idea is tic-tac sized probes with nano circuitry (that doesn't exist yet) accelerated by lasers so they don't have to carry the power source Obviously stopping is the problem, they can never stop but at some point no need

IAmBroom 4mo ago
Before someone mentions IBM's (completely BS) "sub-nanometer circuitry": it isn't nearly sub-nm, except if you look at it from one particular way. The real estate is still many nanometers in dimension. The gates aren't even sub-nano; gate-to-gate interactions are, kind of.