13 June 2008—A consortium of British researchers recently tested a high-speed penetrator—a vehicle meant to deliver sensors and scientific instruments deep below the surface of other planets. The penetrator and all of its instruments survived a 1100-kilometer-per-hour rocket-sledge ride and impact with a sand pile. Accelerometers in the penetrator recorded a deceleration force 20 000 times that of normal gravity, reports Alan Smith, director of the Mullard Space Science Laboratory, at University College London. Humans can survive less than a thousandth of that force.
The vehicle’s first use would be as part of the UK’s proposed MoonLITE mission to the moon, scheduled for launch in 2013 (LITE is short for Lightweight Interior and Telecoms Experiment). It demonstrates a technique that could lower the cost of space exploration by eliminating the need to drill into the moon’s surface.
The test was staged at a UK Ministry of Defence site in Pendine, Wales. The bullet-shaped penetrator was set on a rocket-powered sledge, accelerated, and rammed into a sand pile. ”You see a flash as the motor fires. Everything covers in smoke,” says Smith, who witnessed the test from a protected bunker. Then with a ”whoosh and a thud,” it’s ”all over in about one and a quarter seconds.”
All the vehicle’s instruments—a data-collecting system, a variety of sensors, accelerometers, a seismometer, and a mass spectrometer—survived the impact, says Smith. ”We deliberately used a range of different electronic components and packaging in order to see if some would survive better than others,” he says. The electronics were completely encased, or potted, in solid resin. The fact that nothing was damaged ”was a bit better than expected.”
The electronics weren’t the only area to worry about. The casing itself had to be carefully designed to survive the impact. In this test, it was made from a lightweight aluminum alloy, says Smith. Because it impacted sand—meant to simulate the moon’s surface—the damage to the penetrator was abrasive. The sand shaved off about a millimeter of metal. If the penetrator technology were adapted to explore other places such as Saturn’s icy moon Enceladus or Jupiter’s Europa, the penetrator would probably have to be made of stainless steel or tungsten, says Smith.
The penetrator team plans further trials through spring of next year as it awaits a green light for the MoonLITE mission. The next test will probably include a position sensor and transmitter so the penetrator can radio out how far down it digs.