12-25-2016, 01:26 AM
The problem with beamsails is that (much like photon drives) they are quite inefficient since only a tiny fraction of the photon energy is imparted to moving the ship (since photons must always move at the speed of light). In contrast, a beam-rider can arrange things so that the incoming mass-beam imparts nearly all of its kinetic energy to the ship (leaving the remnants of the beam almost dead in space relative to their origin).
By way of comparison:
Robert Forward's beamsail starship would use 43,000 Terawatts of laser power to accelerate an 80,000 ton ship with 3000 tons of payload (the rest of sail and supporting structures) at 1/3g up to half the speed of light after 1.6 years.
Gerald Nordley's beamrider starship would start out using mass beams operating in the tens of Terawatts to accelerate a 1000 ton ship at 5 gravities (the crew would be in protective acceleration/biostasis tanks for this part) to 86.6% of the speed of light. As the ship went faster and got further away, the energy going into accelerating the mass beam would increase until it peaked at 44,000 TW after 47.4 days of operation. The beam generator then shuts down, although the mass beam itself continues on into space to keep accelerating the ship.
The ship itself takes a full 126 days (from the frame of reference of the mass beam generator, for the ship it's only 96 days) to accelerate, after which it coasts on to its destination. Deceleration could be handled in a variety of ways
Todd
By way of comparison:
Robert Forward's beamsail starship would use 43,000 Terawatts of laser power to accelerate an 80,000 ton ship with 3000 tons of payload (the rest of sail and supporting structures) at 1/3g up to half the speed of light after 1.6 years.
Gerald Nordley's beamrider starship would start out using mass beams operating in the tens of Terawatts to accelerate a 1000 ton ship at 5 gravities (the crew would be in protective acceleration/biostasis tanks for this part) to 86.6% of the speed of light. As the ship went faster and got further away, the energy going into accelerating the mass beam would increase until it peaked at 44,000 TW after 47.4 days of operation. The beam generator then shuts down, although the mass beam itself continues on into space to keep accelerating the ship.
The ship itself takes a full 126 days (from the frame of reference of the mass beam generator, for the ship it's only 96 days) to accelerate, after which it coasts on to its destination. Deceleration could be handled in a variety of ways
Todd