StarTram

History

James R. Powell, who invented the superconducting maglev concept in the 1960s with Gordon Danby at Brookhaven National Laboratory, later co-founded StarTram, Inc. with George Maise, an aerospace engineer formerly at Brookhaven. A StarTram design first appeared in a 2001 paper and patent, referencing a 1994 paper on MagLifter, a maglev launch assist concept developed by John C. Mankins. Both MagLifter and StarTram were discussed in a concept study for NASA's Kennedy Space Center. Subsequent design work produced generation 1, generation 2, and an alternative generation 1.5 variant.

Description

The Gen-1 system accelerates uncrewed craft at 30 g through a 130 km long tunnel. A plasma window prevents vacuum loss when the exit's mechanical shutter opens, and the tunnel is evacuated with an MHD pump. The exit sits on a mountain peak at 6000 m altitude, launching cargo capsules at 8.78 km/s at a 10-degree angle; a small rocket burn of 0.63 km/s circularizes the orbit. A 40-ton cargo craft, 2 m in diameter and 13 m long, experiences peak deceleration of 20 g from atmospheric drag, halving within 4 seconds.

The stagnation-point heating rate reaches about 30 kW/cm2 initially but drops below 10 kW/cm2 within seconds; transpiration water cooling consumes up to about 100 liters/m2 per second. The tunnel has no superconductors or cryogenic cooling; superconducting magnets on the spacecraft induce current in aluminum loops on the tunnel walls for levitation, while a second set of loops carries AC current for acceleration via a linear synchronous motor.

Economics and potential

The StarTram ground facility is claimed to be reusable without extensive maintenance, shifting the requirement for achieving orbit to ground infrastructure. Estimated construction cost is $19 billion for Generation 1 and $67 billion for Generation 2. The Generation 2 goal is $13,000 per person, with up to 4 million people sent to orbit per decade per facility. An alternative Generation 1.5 design would have an intermediate launch velocity of 4 km/s.

Challenges

The largest challenge for Gen-1 is affordable storage, rapid delivery, and handling of power requirements. Electrical energy storage must discharge over 30 seconds with about 50 GW average and about 100 GW peak; SMES cost performance on this scale is anticipated at around a dollar per kilojoule and $20 per kW-peak, novel in scale but similar to other pulsed power systems. Pulsed MHD generators are an alternative.

The single largest predicted capital cost is power conditioning, dealing with up to 100 GW for a few seconds at an estimated $100 per kW-peak. The 130-km acceleration tube spreads energy input over a longer duration, keeping peak power handling at about 2 GW per ton of vehicle. The tunnel itself is estimated at about $4.4 billion, a minority of total system cost.