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Engineering: Current Students

NASA Microgravity University

Engineers Without Borders

The UNL College of Engineering is proud to participate in NASA's Microgravity University. The program engages selected college and university teams in scientific research that helps our nation's space program to refine its efforts. Projects are conducted during a series of parabolic reduced-gravity flights in specially-equipped NASA aircraft that reach 35,000 feet above the earth's surface.

2010 Project:

1. Cryocooler validation for the VASIMR ISS Demonstrator Mission

A flight of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) VF-200 onboard the International Space Station (ISS) is planned for the 2012/2013 time frame. The VF-200 is a high power, 200 kW, plasma rocket prototype that will be used to demonstrate and validate key VASIMR technologies and related plasma exhaust plume physics phenomena in Low Earth Orbit (LEO). The baselined VF-200 design includes a set of High Temperature Superconducting (HTS) magnet assemblies. The low mass and high critical field of the planned HTS assembly will enable the VF-200 and future VASIMR engines to operate at competitive efficiency levels, compared to existing state of the art ion thruster technology, such as the NASA Evolutionary Xenon Thruster (NEXT). The use of cryo-cooler devices is required to keep the HTS magnet assemblies at or below 40 K, 40 degrees above absolute zero, for the duration of the ISS mission. The goal of this proposed microgravity project is to validate the cryo-cooler efficiency levels and cooling capacity reported by the manufacturer in super-gravity,1.8g, and micro-gravity,<0.1g, environments.

The VF-200 design will require 10-12 15 W cryo-coolers to sustain the HTS low-temperature environment. The HTS magnet assembly will reside within a cryo-shield, used to block direct solar and Earth-albedo UV, visible, and IR radiation from heating up the HTS magnet and magnet assembly. Several competing cryo-cooler technologies exist, however due to mass, lifetime, and efficiency considerations, the commercially produced SunPower CryoTel line of cryo-coolers is the leading contender for VF-200 HTS operation. The CryoTel cryo-coolers are an off-the-shelf technology commonly used in low temperature medical, sensor, telecommunications, and pharmaceutical applications. In fact, a slightly modified version of cryo-cooler, the M77, from SunPower has been flown on NASA's RHESSI satellite. A slightly newer model, the M87, will also be used onboard the Alpha Magnetic Spectrometer, a particle detector device that will also reside on the ISS in the 2010/2011 time frame. Though the CryoTel line of cryo-cooler is the successor to the M77 and the M87, the CryTel line has never been operated in a microgravity environment.

This microgravity demonstration is necessary in order to mitigate risk associated with using this off-the-shelf technology for a spaceflight application such as the planned VF-200 mission to the ISS. The students involved in this particular SEED proposal would be requested to:

  1. Construct an acrylic/lexan project box with appropriate electrical and gas/venting feedthroughs. The acrylic/lexan project box should comply with NASA's C-9 safety standards.
  2. Assemble a data acquisition system to log pressure and low temperature thermal data throughout the flight.
  3. Design of a simple cryo-shield to possibly include Multi-Layer Insulation (MLI) to insulate the cryo-cooler cold heads from the ambient temperature cryo-stat vacuum vessel walls.
  4. Identify component and system failure modes of the SEED experiment and mitigate experiment failure probability through design choices and design iteration.

We have partnered with SunPower, and there is a partnership in place to support the testing of at least one, but mostly likely 2 or 3 CryoTel cryo-cooler designs. The cryo-coolers will be loaned to us for this testing purpose. A small vacuum vessel will be provided by the proposer (Ad Astra Rocket Company) to insulate the cold head of the cryo-coolers from atmosphere. The vacuum vessel is used to keep the air from condensing out onto the cold head. At the temperature range of interest, ~40 K, nearly all atmospheric gasses solidify into an ice. A vacuum pump will also be provided by the proposer in order to evacuate the vacuum vessel. The proposer will also provide existing in-house vacuum lines and vacuum pressure measurement equipment for the SEED experiment. The PI and the support NASA contractor lab, the Ad Astra Rocket Company, are located in Webster TX, 1.5 miles from the Johnson Space Center and 2 miles from Ellington Field.

The students and faculty advisor will be given extensive laboratory tours of the Ad Astra facilities, including a 150 cubic meter space simulation vacuum chamber and the VX-200, a ground prototype of the VF-200 ISS testbed. The potential exists for highly motivated students to be invited to spend an internship at the Ad Astra Rocket Company, further developing the VF-200 cryo-cooler design. Benjamin Longmier

Important Dates

Flight Week: May 30 - June 7, 2014

2014 Contacts


Team Red Moon Leader:
Kevin Watts

Faculty Advisors:
Zhaoyan Zhang
Carl Nelson

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