# Novel way for interstellar travel

## Main Question or Discussion Point

Suppose there was a ring of some material (steel? future carbon nano tubes?) around the sun. The ring would have a diameter of 2*10^9th meters. If a solar sail were placed attached to the ring with the reflector at a 45 degree angle) then the solar sails velocity would only be limited by the strength of the material (ability to handle the accelearation and for the ring to stay connected). Still, I calculate that even with the centrifugal force of 10^6 (the same acceleration experienced by a bullet) this would net a velocity of 1/10th the speed of light. So it could take about 40 years to reach the nearest star. The benefit of this means of gaining velocity is that all your energy would be provided by the sun free of charge...it would just take time for the solar sail to reach that speed. The total circumference of the ring would be equivalent to 25X the circumference of the earth...and you wouldn't need it to do anything more than hold together until the sail detached. Any thoughts?

Related Astronomy and Astrophysics News on Phys.org
UltrafastPED
Gold Member
It wouldn't hold together; it wouldn't hold together even if it wasn't accelerated.

Among other problems it would be unstable wrt the sun - read any review of the scientific problems with "Ringworld".

Also have you calculated how long it would take to accelerate up to .1c? What is the mass of your ring?

You should attempt some calculations and see what you get.

Thank you.... and just to be clear, I am not looking to accelerate the ring, only the solar sail. the solar sail would accelerate around the ring. Perhaps to reduce friction the ring could be magnetized and the sail sit off the ring via magnetic repulsion. But maybe a ring attached around the moon for solar system travel would be better/more realistic.

Also, as you pointed out, I found the mass of the ring would be considerable if made out of steel. If 1 cubic meter of steel was needed then it would require an equivalent of 100,000 world trade centers in mass for the ring. If the ring need only be 10 cm^2 and 1meter long then it would still need 1000 world trade centers in mass.

Chronos
Gold Member
You would need about 12,250 kg of oxygen, 14500 kg of water and 13250 kg of food per person for a 40 year journey. That totals about 40 metric tons of basic survival supplies per person. It gonna be one big ship.

Astronuc
Staff Emeritus
Suppose there was a ring of some material (steel? future carbon nano tubes?) around the sun. The ring would have a diameter of 2*10^9th meters. If a solar sail were placed attached to the ring with the reflector at a 45 degree angle) then the solar sails velocity would only be limited by the strength of the material (ability to handle the accelearation and for the ring to stay connected). Still, I calculate that even with the centrifugal force of 10^6 (the same acceleration experienced by a bullet) this would net a velocity of 1/10th the speed of light. So it could take about 40 years to reach the nearest star. The benefit of this means of gaining velocity is that all your energy would be provided by the sun free of charge...it would just take time for the solar sail to reach that speed. The total circumference of the ring would be equivalent to 25X the circumference of the earth...and you wouldn't need it to do anything more than hold together until the sail detached. Any thoughts?
There are quite a few problems with this scenario, and with the OP.

One proposes to construct a ring with a diameter larger than the sun. Then attach a sail - ostensibly larger than the sun. Where would one propose to collect that amount of material in the solar system.

The "centrifugal force of 10^6" is missing units, and it's not clear how it applies to the sail, or from where such a number is derived.

Checking some numbers - http://solarsystem.nasa.gov/planets/profile.cfm?Display=Facts&Object=Earth - the earth's equatorial circumference is about 4 E7 m, and 25x that is 1 E9 m, which is about half the diameter of the proposed ring.

How long would it take to construct such an immense structure? To what would it be tethered during contruction?

As the solar sail moves away from the sun, the solid angle subtended by the sun decreases. The pressure from the solar light falls off ~ 1/d2. Out past Jupiter, the sun looks pretty small, and that's not very far compard to the edge of the solar system.

Finally, this is not astrophysics.