In this case the 9 GW solar pumped laser is used with a large projector system launched by a second BFR to beam energy from Earth orbit to the vicinity of Jupiter. This makes use of a solar pumped laser power satellite that is developed to be deployed by the BFR system - and operate to generate energy for use on Earth and other inhabited worlds.

This also is used as an energy storage medium to take water carried aboard ship, along with water ice found in situ - and produce hydrogen and oxygen with it using laser energy received from Earth. This permits the ship to carry out maneuvers without being illuminated by the laser beam. The other 700 tonnes of propellant is used in a hydrogen/oxygen rocket through the same nozzle which has a 4.5 km/sec exhaust speed (I sp of 450 sec). So, an extended BFR spacecraft that consists of a 150 tonne payload and 170 tonne structure (twice the 85 tonne structure weight of a standard BFR starship) which includes a hydrogen tank that carries 500 tonnes of liquid hydrogen in a long duration zero boil off tank, as well as 600 tonnes of LOX, along with large inflatable concentrators.Ī laser beam is focused on the ship and the receiver optics focus the laser beam into the engine where it heats liquid hydrogen to 40 km/sec (exhaust velocity of 40,000 m/s, specific impulse of 4,000 sec). e x = antilog base e or inverse of natural logarithm of x, the 'e x' key on your calculator.ln = natural logarithm of x, the 'ln' key on your calculator.Bε = efficiency with which engine converts beam power into exhaust kinetic energy (0.0 to 1.0, currently about 0.3).Bp = Beam power (watts) of either laser beam or solar energy collected.Δ v = ship's total deltaV capability (m/s).The equations for delta V and mass ratio are slightly different for a Solar Moth or Laser Thermal rocket engine: Having said that, the Mirror Steamer has an alternate solution. The seeding make the hydrogen more opaque so the blasted stuff will heat up. As always the reason for seeding is that hydrogen is more or less transparent so the laser beam will mostly pass right through without heating the hydrogen. Propellant is hydrogen seeded with alkali metal. The drawback include the fact that there is a maximum effective range you can send a worthwhile laser beam from station to spacecraft, and the fact that the spacecraft is at the mercy of whoever is controlling the laser station. In some science fiction novels, combat 'motherships' will have batteries of lasers, used to power hordes of ultra-high acceleration missiles and/or fighter spacecraft. The reduced mass also increases the acceleration. Or the reduced mass makes for a higher mass ratio to increase the spacecraft's delta V. With the mass of the power plant not actually on the spacecraft, more mass is available for payload. Basically the propulsion system leaves the power plant at home and relies upon a laser beam instead of an incredibly long extension cord.Īs a general rule, the collector mirror of a laser thermal rocket can be much smaller than a comparable solar moth, since the laser beam probably has a higher energy density than natural sunlight. Similar to Solar Moth, but uses a stationary ground or space-station based laser instead of the sun.

Deliver us the moon rotation engine 3