Reduced shielding mass for the vista spacecraft

الملخص EN

An innovative concept for the direct utilization of fusion energy with laser ignited (D,T) capsules for propulsion is presented with the so called VISTA (Vehicle for Interplanetary Space Transport Applications) concept.

VISTA’s overall geometry is that of a 50°-half-angle cone to avoid massive radioactive shielding.

The 50°-halfangle maximizes the jet efficiency, and is determined by selecting the optimum pellet firing position along the axis of the cone with respect to the plane of the magnet coil.

The pellet firing position is in the vacuum.

Assuming a total fusion power production of 17 500 MW with a repetition rate of 5 Hz and 3500 MJ per shot, the propulsion power in form of charged particles has been calculated as ~7000 MW, making ~40% of the total fusion power.

About 60% of the fusion energy is carried by the leaking neutrons out of the pellet.

Most of them (96%) escape into vacuum without striking the space ship.

Only 4% enter the frozen hydrogen expellant in the conical shape (about 50 gr.).

Two design limits are discussed, 5 and 1 mW/cm3.

Total peak nuclear heat generation in the coils is calculated as 4.7 mW/cm3.

The peak neutron heating is 1.9 mW/cm3 and the peak γ-ray heating density is 2.8 mW/cm3.

However, volume averaged nuclear heat generation in the coils is much lower.

It is calculated as 0.18, 0.48, and 0.66 mW/cm3 for neutron, γ-ray, and total nuclear heating, respectively.

With higher design limits for nuclear heat generation in the coils and using natural lithium in the shielding, it was possible to reduce the net shielding mass from 595 tonne down to 170 tonne, making <3% of the vehicle mass, by a total vehicle mass of VISTA ~6 000 tonne