Dana Andrews had looked at a near term system for achieving 2% of the speed of light. It used an advanced ion drive and a couple of small nuclear reactors. It would weigh 4000 tons which is about the mass of some nuclear submarines. It was also a bit more than the 3350 tons of the Saturn V.
We do not have advanced ion drive now and we do not have the proposed small nuclear reactors. It will likely take 10-30 years to develop them.
We also do not have working magnetic or e-sail systems for slowing ships down at target stars.
We have had the technical capability and knowledge to make spaceships that can travel at 2-10% of light speed. The more moderate size ships of 4000-10000 tons could go up to 2% of lightspeed and at 400,000 tons a ship could go up to 4% of lightspeed.
The technology was of course Project orion, nuclear pulse propulsion.
A preliminary design for a nuclear pulse unit was produced. It proposed the use of a shaped-charge fusion-boosted fission explosive. The explosive was wrapped in a beryllium oxide channel filler, which was surrounded by a uranium radiation mirror. The mirror and channel filler were open ended, and in this open end a flat plate of tungsten propellant was placed. The whole unit was built into a can with a diameter no larger than 6 inches (15 cm) and weighed just over 300 pounds (140 kg) so it could be handled by machinery scaled-up from a soft-drink vending machine; Coca-Cola was consulted on the design.
At 1 microsecond after ignition the gamma bomb plasma and neutrons would heat the channel filler and be somewhat contained by the uranium shell. At 2–3 microseconds the channel filler would transmit some of the energy to the propellant, which vaporized. The flat plate of propellant formed a cigar-shaped explosion aimed at the pusher plate.
The plasma would cool to 14,000 °C as it traversed the 25 m distance to the pusher plate and then reheat to 67,000 °C as, at about 300 microseconds, it hits the pusher plate and is recompressed. This temperature emits ultraviolet light, which is poorly transmitted through most plasmas. This helps keep the pusher plate cool. The cigar shaped distribution profile and low density of the plasma reduces the instantaneous shock to the pusher plate.
The pusher plates thickness would decrease by, approximately, a factor of 6 from the center to the edge so that the net velocity of the inner and outer parts of the plate are the same, even though the momentum transferred by the plasma increases from the center outwards.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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