B Can a solar sail be accelerated 20% speed of light

[wolram]

This seems over optimistic to me but is 20% the speed of light feasible?
https://www.sciencedaily.com/releases/2017/02/170201162456.htm

 

[Borg]

This seems over optimistic to me but is 20% the speed of light feasible?
https://www.sciencedaily.com/releases/2017/02/170201162456.htm

It makes me wonder what kind of energy that would have if it accidently entered the atmosphere of a planet at the destination without any braking.

 

[lifeonmercury]

What would happen?

 

[stefan r]

No. not in a reasonable timeframe. However, A light sail could. We would need to shoot lots of lasers at the sail. Solar luminosity decreases with distance.

 

[stoomart]

Recently discussed at length, post 27 gets into problems with using solar power.

https://www.physicsforums.com/threads/beam-powered-propulsion-keeping-the-beam-focused.896207/

 

[mfb]

This seems over optimistic to me but is 20% the speed of light feasible?

If you make the sail thin enough, everything gets possible - apart from building such a sail.

 

[anorlunda]

If you make the sail thin enough, everything gets possible - apart from building such a sail.

That's exactly right. In the 1970s, I saw a proposal to build a solar sail the size of The Moon, but weighing only 1 gram. It would be made of aluminum foil only two atoms thick. IMO, deploying it and holding it in shape and orientation would be even more difficult than building it.

Back to the OP. Your question can't be answered without specifying the size and mass of the sail and the payload, and the mission.

 

[newjerseyrunner]

If you make the sail thin enough, everything gets possible - apart from building such a sail.

That's not true, you can't make a sail go faster than the wind. The solar wind travels around a million miles an hour, so that's where it'd max out. Plus a small boost from light pressure, but that'd be negligible by comparison wouldn't it?

 

[anorlunda]

That's not true, you can't make a sail go faster than the wind. The solar wind travels around a million miles an hour, so that's where it'd max out. Plus a small boost from light pressure, but that'd be negligible by comparison wouldn't it?

Not solar wind, but rather light from powerful lasers would be the propulsion source. In the 1970s proposal I mentioned in #7. they talked of lasers in close solar orbit that would accelerate the sail until it got out to about the orbit of Jupiter, achieving 1/3 light speed. Of course the proposal was speculative, not practical.

Edit: I just realized that to achieve 1/3 light speed with uniform acceleration from solar orbit to Jupiter's orbit, the duration of the acceleration phase is only about 4 hours. Even allowing for a more accurate calculation, the lasers need to survive for only a very short time.

 

[stefan r]

...
Edit: I just realized that to achieve 1/3 light speed with uniform acceleration from solar orbit to Jupiter's orbit, the duration of the acceleration phase is only about 4 hours. Even allowing for a more accurate calculation, the lasers need to survive for only a very short time.

So a foil in front of a series of nuclear blasts? Maybe place the nukes in a line and trigger them as the foil/plasma passes?

Starshot is claiming 4.7% of light speed. They are assuming a functional graphene sheet, a reflective atomic monolayer coating, and a computer printed into that sheet and layer.

 

[Physics_Kid]

wouldn't the smallest of friction from solar dust be an issue for anything that has mass made from earthly materials while traveling at that speed? or is this 20%*c the estimate based on materials and friction?

 

[stefan r]

wouldn't the smallest of friction from solar dust be an issue for anything that has mass made from earthly materials while traveling at that speed? or is this 20%*c the estimate based on materials and friction?

An article in Scientific American had 1 laser array and at least one rocket launch. Each probe weighs a few grams. So each launch package contains thousands of probes. The laser array accelerates one probe for a few minutes. The probes can be sent separately. You can do one probe a day or several per hour. Most of the probes will be mangled or destroyed before getting to Alpha Centuari. The hope is that more than one of the thousands sent are still able to send back data.

The sail does not need to work on the other end if it is a flyby. If they plan to slow down then the sail has to fold/roll into something like a needle. One of them might still work with some holes.

Finding out how much dust is between here and Alpha Centuari would be information gain.

 

[John Park]

That's not true, you can't make a sail go faster than the wind. The solar wind travels around a million miles an hour, so that's where it'd max out. Plus a small boost from light pressure, but that'd be negligible by comparison wouldn't it?

Actually solar radiation pressure is three or four orders of magnitude higher than the pressure of the solar wind (at 1 AU)--see for example Wikipedia.

 

[Simon Peach]

How would the nuclear explosives get there?

So a foil in front of a series of nuclear blasts? Maybe place the nukes in a line and trigger them as the foil/plasma passes?

Starshot is claiming 4.7% of light speed. They are assuming a functional graphene sheet, a reflective atomic monolayer coating, and a computer printed into that sheet and layer.

how would the nuclear explosives get there?

 

[John Park]

how would the nuclear explosives get there?

Hmm. Could you use them within the solar system and coast the rest of the way?

 

[Simon Peach]

So the trip is going to be slow anyway, first you're going to set the explosives off on their way then send the "vehicle" off hope all the time that you've got the orbital mechanics worked out correctly so the "vehicle" passes very close to the explosive, but not too close that the "sail" is damaged and not too far that the explosion is ineffective.

 

[Simon Peach]

Has the speed of say 10x⁵g object been calculated with say 10² x ⁵m sail when it gets out of the heliosphere?