November 12, 2013

Sample Return from hypervelocity flyby's of Moons and Asteroids

Since the Apollo era, sample return missions have been primarily limited to asteroid sampling. More comprehensive sampling could yield critical information on the formation of the solar system and the potential of life beyond Earth. Hard landings at hypervelocity (1-2 km/s) would enable sampling to several feet below the surface penetration while minimizing the Delta V and mass requirements.

Combined with tether technology a host of potential targets becomes viable. The proposed work seeks to design, develop and test a hard impact penetrator/sampler that can withstand the hard impact and enable the sample to be returned to orbit. Tether technology for release of the penetrator and capture of the sample eliminate many of the restrictions that presently inhibit the development of sample return missions. The work builds upon in hypervelocity laboratory testing that use 1" Al projectiles that investigate crater formation and penetration through hard surfaces. The proposed work will enable realistic size (6" diameter) projectiles to be studied by taking advantage of the development of cheap high power commercial rocket motors that will enable impacts up to Mach 2 for Phase I. With this data, methodologies for studying higher velocity impacts can be developed along with mission scenarios to test the viability of mission return samples in the near future. Successful development of sample return capabilities will provide a major impetus for solar system exploration.

A rocket is hoisted by kite in the Nevada desert, then fired into a dry lakebed to test the idea of using a tethered rocket to collect and return samples from forbidding environments. The launch was conducted by a University of Washington class in Earth and space sciences in March 2013.

“We’re trying to figure out what the maximum speed is that a rocket can survive a hard impact,” said Robert Winglee, a UW professor of Earth and space sciences, who heads that department and leads the annual trek to the desert.

The idea for a project called “Sample Return Systems for Extreme Environments” is that the rocket will hit the surface and, as it burrows in a short distance, ports on either side of the nose will collect a sample and funnel it to an interior capsule. That capsule will be attached by tether to a balloon or a spacecraft, which would immediately reel in the capsule to recover the sample.

While many missions use Hexcel, a honeycomb-structured aluminum material with built-in give, the team has found it insufficient to survive the high-speed collision. It would need a "much higher strength to weight ratio," according to the research paper submitted to the NASA Innovative Advanced Concepts (NIAC) program, a program that searches for the next generation of ideas in space exploration. To reinforce the collapsible aluminum material, they're looking at a variety of foam epoxies that can help the material bounce back from a collision.

Small ports in the nose cone trap samples, which collect in the center of the ports. Getting the samples back to the craft is just a matter of pulling a tether back up, accomplished through a combination of the speed of the craft itself pulling on the tether, some thruster support, and a high-tension cable that reels it in, not unlike a fishing pole. Winglee eventually wants to incorporate onboard electronics to do other analysis, including seismic measurements and preliminary analysis, and multiple samplers might be deployed in future missions. And because the craft isn't going into orbit, it has the momentum it needs to return home once the samplers are returned, saving more on fuel costs.

(a) CAD drawing of the proposed spacecraft, (b) movement of one of the penetrator into its lowering position with the attached on the tether, (c) lowering of the penetrator with the tether and (d) return of the sample by the tether to the spacecraft where is can be stored in its initial position.

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