PARACHUTES made of plasma trapped in a magnetic field could soon be helping space probes glide safely back to Earth.

Two private aerospace companies have to demonstrate magnetoshell aerocapture, a way of shrouding a falling spacecraft in a magnetic bubble akin to the plasma shield around Earth. But whereas Earth’s magnetosphere protects it from solar radiation, a similar bubble around a spacecraft creates drag, slowing it down. If a test next year proves successful, the technique could help future probes land heavy loads on Mars or bring back human missions to deep space.

“I’m really excited about these awards that have been made,” says at NASA’s Space Technology Mission Directorate in Hampton, Virginia. “It’s a low-cost way to investigate these kinds of things and see if they will bear fruit.”

When a spacecraft enters a planet’s atmosphere, it ploughs into air molecules at high speed, creating intense heat. Structures designed to create drag can slow the descent, but probes must also rely on heat shields that either burn away or insulate to protect the cargo inside. The heavier the payload, the more challenging the task of getting the craft down in one piece.

For larger landers, NASA has been looking at lightweight technologies such as an inflatable “flying saucer” for Mars missions, tested last week over Hawaii (see ‘Flying saucer’ makes a splash). Magnetoshell aerocapture is one of the most revolutionary ideas, says Munk. It not only slows a craft’s descent but can also greatly reduce heating.

Last month, aerospace firm of Redmond, Washington, won a NASA grant to demonstrate the technique on a CubeSat. The small, boxy satellite should be delivered to the International Space Station in 2015. It will then be deployed and attempt to enter Earth’s atmosphere without burning up.

The satellite will carry a copper coil, powered by a lithium-ion battery, that generates a magnetic field around the probe. As it descends, the spacecraft will eject a small amount of plasma. This gets trapped in the magnetic field, creating a protective bubble that stops air molecules colliding with the craft and producing heat.

The air molecules flow into the plasma bubble and absorb electrons from it, becoming ionised. The newly ionised air becomes trapped in the magnetic field, and the craft ends up dragging a patch of atmosphere with it, effectively creating a parachute of gas.

The CubeSat’s magnetoshell aerocapture system will be built by of Louisville, Colorado. NASA awarded it a contract to develop such systems, which will feature an external magnetic coil up to 5 metres across. These could be used on larger landers, including human missions to deep space that need to return to Earth, says Altius’s Jonathan Goff.

“The technique could be used on human missions to deep space that need to return to Earth”

The system has hefty power requirements that will strain the limits of any battery the CubeSat could carry, says Goff. But if the test succeeds, it could also boost efforts to make rockets reusable, allowing parts discarded in orbit to return to Earth intact, he says. “Basically it’s a way of moving beyond the Apollo throwaway philosophy.”

This article appeared in print under the headline “Magnetic shroud is the secret to a soft landing”

RICHARD BROWN is a man with unfinished business. In 1999, he smashed the one-way speed record for a motorbike by hitting 584 kilometres per hour on the salt flats of Bonneville in northern Utah. But his claim on the outright world record – which is based on the average of two runs in opposite directions – was thwarted by technical problems.

Now he is trying again. He hopes to be the first person to exceed 720 km/h on a .

While cars used in land-speed-record attempts, like the Bloodhound jet car that will attempt the challenge in 2012, and certain types of boat have taken advantage of jet thrust since the 1950s, all record-breaking motorbikes have used a conventional engine that drives the rear wheel.

This is because it is difficult to pack a jet engine into a two-wheeled frame capable of enormous speed with any degree of safety. Fast cars can be built around old jet fighter engines, but these are far too heavy to fit into a bike that must be balanced by the driver making tiny steering adjustments to the front wheel.

So for his new bike, called Jet Reaction, Brown has redesigned a 930-kilowatt helicopter engine to produce thrust instead of turning a rotor. It was “quite difficult”, he says. “One is working with very fine tolerances in very difficult materials. If you get it wrong, destroying the engine is the most likely result.”

“Get the redesign of the helicopter engine wrong, and the most likely result is that it will be destroyed”

Brown has also added his own reheat unit, or afterburner. It sprays fuel into the hot exhaust gases, causing it to ignite and generate yet more thrust. The idea sounds simple enough, though he says that getting it to work at something approaching its theoretical potential “requires much more development”. The reheat burner sits above two canisters that deploy braking parachutes when needed.

Brown has a track record in ambitious jet engine projects. Following his 1999 record attempt he built a sub-orbital rocket, but the launch in South Africa had to be cancelled. He is also working on a gas-turbine-powered jet pack, similar to one developed by the US military, that he hopes will allow the wearer to remain airborne for 10 minutes.

”ț°ùŽÇ·ÉČÔ’s involved his own Gillette Mach 3 Challenger bike, which featured a custom-built hybrid rocket engine. The attempt failed because soft ground forced the team to use tyres rather than the usual aluminium wheels. The tyres were only designed to withstand speeds of 380 km/h or so. Eventually the massive centrifugal forces on the rear tyre caused it to deflate.

The current motorbike land-speed record, 606 km/h, was set in 2010 by Rocky Robinson on a bike called the Ack Attack Streamliner. Such record-breakers feature elongated metal bodies – as does Jet Reaction – making them look more like giant bullets than motorcycles. They are also fitted with retractable stabilisers for balance when moving slowly or stationary.

Brown expects to carry out trials with Jet Reaction at a UK airfield in March next year, with an attempt on the world record back at the Bonneville salt flats pencilled in for 2013.

It won’t be easy, says Mark Chapman, Bloodhound’s chief engineer. “The biggest issue is air intake,” he says. “You have to be sure the air flow through the jet is stable or the engine could surge, which could be dangerous.”

Update 14 September The Armadillo Aerospace team succeeded in making a pair of 180-second flights between two pads on 13 September

Over the coming weeks, three teams will try to complete the second and final stage of the Lunar Lander Challenge (LLC), sponsored by NASA and aerospace company Northrop Grumman.

Last October, of Texas won level one of the challenge and $350,000 by building a rocket that made two 90-second flights, reaching an altitude of 50 metres, between flat concrete pads 100 metres apart. On Saturday, they will be aiming for the million-dollar prize for the more challenging level two.

The aim this time is to complete two flights, each lasting 3 minutes. If it can stay aloft in Earth’s gravity for that long, the vehicle would have enough power to take off from the surface of the moon and go into lunar orbit.

The vehicle also has to land on a rough landscape, akin to a lunar landing site. Armadillo created their mock moonscapes at Caddo Mills airfield in Texas, using rocks and gravel.

Super Mod

Armadillo’s vehicle, the , is propelled by a rocket engine burning a blend of liquid oxygen and alcohol. Like the Apollo landers, it is steered by changing the angle of the main engine.

The Super Mod is the largest of the vehicles in the contest and, if flown at full power, should be able to reach an altitude of 100 kilometres – sometimes considered the edge of space. The technology is modular, so several Super Mods could be bolted together to make a more powerful vehicle. According to Armadillo’s John Carmack, six of them put together could complete the lunar lander challenge with a pilot on board.

Xombie

Before the end of October, and , both based in California, will also be vying to win level two.

Masten are following a similar approach with their XA 0.1B, nicknamed Xombie, which uses the same fuel and method of steering (see image). The is a technology demonstrator for larger vehicles that Masten hopes to start flying next year, with the long-term goal of providing cheap suborbital launch services for scientific missions and space tourists.

Blue Ball

Unreasonable Rocket is a much smaller team, consisting of father and son Paul T Breed and Paul A Breed. Their vehicle, the , is powered by hydrogen peroxide, which produces thrust as it decomposes to steam and oxygen when passed through a silver mesh (see image).

With just a single propellant, the rocket needs only one tank and control valve, much simpler than dealing with two liquids that burn together. It can also be stopped and started easily and is very reliable, but on the downside, the performance of hydrogen peroxide is only about 60 per cent of what can be achieved with two liquids.

While the Blue Ball is just over 1.5 metres high – much smaller than its competitors and therefore further from a human-scale lander – it could form the basis of lunar probes.

NASA’s sponsorship of the prize is not directly connected to their plans, still uncertain, for a return to the moon. “The LLC was never intended to develop technologies for actual lunar landing,” Carmack told żìĂš¶ÌÊÓÆ”. Instead, the hope is that it will encourage the development of new space-technology firms.