Double TARS

In the previous post I discussed how the TARS concept could take advantage of the conservation of angular momentum to reach its maximum launch speed sooner by drawing mass in toward its axis of rotation, like a figure skater drawing their arms in. Besides reaching max speed sooner, fully drawing in the sheet would also hide the reflective surface area, thus cutting solar pressure and stopping runaway acceleration of spin that would eventually tear the sheet apart. Now that we can preserve the sheet, we need to figure out how to slow down its spin so new payloads can be added.

One possibility might be to have a solar panel powering an electric motor that can counter the sheet's spin. A more in-kind solution would be to attach the TARS sheet to a second TARS sheet that has its reflectivity reversed, like this:

In the initial setup, only one sheet would be unfurled, allowing solar pressure to initiate spin:

Once the assembly is spinning fast enough, the extended sheet is pulled in, increasing its speed by conservation of angular momentum and approaching the limits of the material's tensile strength. At that point payloads can be released from both sheets, which are spinning at the same rate:

Retracted, the sheet no longer experiences solar pressure and spins faster and faster to the point it destroys itself. But it does continue to spin. To slow it down, we can unfurl the second sheet, which immediately reverts the spin to the slower rotation the assembly had before the first sheet was drawn in. Also, since the second sheet has swapped which side is reflective, solar pressure on the second sheet begins to counteract the spin of the whole assembly and slow rotation.

Once the assembly stops rotating, new payloads can be installed and the whole assembly spun up again to repeat the process.

The weakest point of this setup is likely the rod connecting the two sheets, which would have to be strong enough to withstand the twisting forces caused by the changes in angular momentum when sheets are pulled sheets in and let. The force of the counteracting spin, though, should be minor.

While this setup doesn't require a power source or electric motor to spin down the apparatus, it does require them to pull in the sheets.

If you have thoughts on this idea, please email me.