Video: High-speed penetrators that could one day be used to breach the surfaces of planets or moons have passed their first test, accelerating to 1100 km per hour before striking their target (Courtesy of UCL)
A UK plan to drive four 鈥榤issiles鈥� into the Moon to study its internal structure recently got a boost when tests suggested the missiles鈥� instruments would survive the violent impact.
The probes, part of a proposed UK-NASA collaboration called MoonLITE, could launch as early as 2013. Each would carry a seismometer on board. Together, the network of sensors could use the energy of to map the Moon鈥檚 interior and help reveal whether the Moon has an iron core, which could shed light on how it formed. A drill and instruments to test for water and other chemicals will also be on board.
Each 鈥榩enetrator鈥� may hit the Moon鈥檚 surface at a speed of more than 1100 kilometres per hour, rapidly coming to a halt as much as 3 metres into lunar dust.
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In recent tests, the penetrators were driven by a rocket-powered train into a pile of sand at the speed they would likely hit the Moon. The collision decelerated the load by 10,000 times the strength of gravity 鈥� by comparison, ordinary rockets typically do not experience vibrations of more than 100 gs.
The probe鈥檚 scientific instruments seemed to survive the heavy jolt, says project lead Alan Smith of University College London鈥檚 Mullard Space Science Laboratory in Surrey, UK. 鈥淲e鈥檙e very very pleased,鈥� Smith told New 杏吧原创. 鈥淲e achieved far more than we expected in a very short time.鈥�
Light and rugged
To enable the penetrators鈥� scientific instruments to survive the impact, Smith and colleagues embedded the probes鈥� electrical components in a clear block of epoxy and bolted down everything else. Silicon microelectronics were used in some instruments to make the probe lighter and more rugged.
The probes might be able to push metres down into the lunar surface before stopping. But exactly how far is unclear. 鈥淭he Moon regolith is not like sand. It鈥檚 more like compressed talcum powder,鈥� says Smith. 鈥淚t does make it harder to penetrate.鈥�
If all goes well, the penetrators might be the first to successfully crash into an extraterrestrial object and survive to carry on measurements. The last such attempt to slam instruments into a lunar or planetary surface was in 1999, when NASA鈥檚 Deep Space 2 mission sent two miniature probes to the surface of Mars.
Organic chemistry
Although the probes seemed to have impacted the surface, the agency was never able to establish communication with them. Other missions have focused on creating impacts to kick up dust or other debris that could be analysed by an orbiting spacecraft.
Communication and power can be two challenges when it comes to developing such impacting probes, says Phil Christensen at Arizona State University in Tempe, US. 鈥淏ut penetrators have always been on the horizon,鈥� says Christensen. 鈥淭here鈥檚 certainly a lot of things you could do if you poke things into the ground.鈥�
On the ground, an impacting probe should be more sensitive to components like organic chemicals than an orbiter studying a plume of soil ejected by a 鈥榙ummy鈥� penetrator would be, Christensen says.
Smith says a radioactive source should be able to keep each probe鈥檚 electronics warm in the cold environment of space. The probes should still be able to communicate by radio through the lunar soil, as it is relatively dry, he adds. Crashing into other bodies in the solar system might require a more creative fix, since moisture can affect the propagation of radio waves.
