Design News is part of the Informa Markets Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

NASA quickens pace, lowers risks on new projects 9/6/99

Article-NASA quickens pace, lowers risks on new projects 9/6/99

NASA quickens pace, lowers risks on new projects 9/6/99

Research and development of an untried technology has always been risky business. What if it doesn't work? How can the cost be justified? Will the company be able to recover the money and time devoted to the project?

NASA understands these concerns. So the government agency decided to shoulder some of this industry burden. NASA's New Millennium Program (NMP) examines risky technologies and looks to validate breakthrough inventions that will potentially aid both commercial industries as well as future space exploration projects. NMP's two main objectives are:

Accelerate the development of new, space-applicable technologies currently in development in laboratories by testing them in space.

  • Reduce the risk and cost to future programs by conducting dedicated, technology-testing missions now.

"We are acting as guinea pigs," says Fuk Li, NASA's NMP manager.

Since the NMP began in 1994, an extensive panel of experts from the government, industry, and academia has sorted through thousands of prospects. To even be considered, a proposal must pass three fundamental criteria.

"We first look at the technology needs of future NASA space and earth science studies," says Li, "and ask, 'Does this project serve high-priority science?'"

If yes, the group examines the maturity level of each technology to see if it meets the performance requirements to warrant an investment. "We always ask if it is revolutionary rather than evolutionary," says Bryant Cramer, NMP implementation manager, Goddard Space Flight Center (Greenbelt, MD).

The last, rather obvious criterion for NASA, is whether or not the technology will need a flight evaluation to determine its worth.

After a program meets these requirements, NASA re-examines its relevancy and re-evaluates based on cost.

Originally, six projects made the cut. Four focus on space exploration and two on earth-observing technologies. Here's a look at those currently underway:

Earth Observing-1:

Advanced Land Imager

Launch Date: July 15, 1999

Earth Observing-1 Mission will fly three advanced land imaging instruments. The Advanced Land Imager (ALI) is a new generation of Landsat instruments with 1/4th the mass and volume of the older version, yet produces four times the data output. Like its predecessor, Landsat 7, the ALI is a multispectral imager covering many electromagnetic frequency bands. With a 15-degree field-of-view telescope and partially populated focal plane occupying 1/5th of the field-of-view, the ALI takes a ground swath width of 37 km with a 30-m spatial resolution. Four silicon carbide mirrors enable the use of large detector arrays in the focal plane, allowing the ALI to cover a swath of 185 km equivalent to Landsat 7.

To help reduce ALI's weight yet keep the properties they wanted, engineers used silicon carbide for the optics. Silicon carbide has thermal stiffness, high thermal conductivity, and low thermal expansion properties. "These are the largest silicon carbide mirrors ever produced," says Cramer, "yet they are housed in a smaller packaging. They have a wide field of view with no moving parts."

The second instrument on the EO-1 mission is the Hyperion or Hyperspectral Imager. "We are the first to use a hyperspectral imager for land images," says Cramer.

The Hyperion is a grating imaging spectrometer. Each image frame taken in this push broom configuration captures the spectrum of line 30-m long by 7.5 km wide, which then "sweeps" across the Earth's surface due to satellite motion. This also has no moving parts. To keep the size down, engineers laid the diffraction gratings used as filters on top of the detection arrays. The unique grating-based design is what makes the instrument so powerful, says Cramer. "The gratings are extraordinary."

Another first for the EO-1 is its carbon/carbon radiator that also serves as a load bearing structure.

Deep Space 1:

Ion propulsion

Launch Date: October 24, 1998

Aerospace engineers have researched the ion propulsion engine since 1959. "But it was a technology way ahead of its time," says Michael Patterson, aerospace engineer at NASA's Glenn Research Center (Cleveland, OH). Finally, the ion engine is a reality. Deep Space 1 took off in late October 1998. The first time such an engine has powered planetary space travel, says Patterson. And so far, it has been an overwhelming success.

Ion propulsion involves ionizing a gas to propel a craft. Here xenon is ionized or charged and electrically accelerated to about 30 km/second. The xenon ions are emitted as a high-speed exhaust from a spacecraft.

The ion propulsion system (IPS) uses a hollow cathode to produce electrons to collisionally ionize xenon. The Xe+ is electrostatically accelerated through a potential of 1,200V and emitted from the 30-cm thruster through a set of closely-space molybdenum grids. Electrons are then injected into the beam to produce a neutral plasma.

"Until recently, ion technology had been considered too exotic," Patterson says. "Opponents would say things like, 'It doesn't look like a rocket engine.'"

To help gain user acceptance, engineers had to demonstrate a thruster lifetime of 7,000 hours or nearly one year of continuous operation. But how do you demonstrate that kind of lifetime in ground testing while simulating space-like conditions? With large vacuum chambers and extremely high pumping speeds, says Patterson.

Breakthroughs in hollow cathode technology, initiated in 1992 for the Space Station plasma contactor system, ensured that the thruster was equipped with long-life cathodes. "Up until 1992, we couldn't get cathodes to operate on inert gas propellants for more than about 500 hours without failing, with only 20 ignitions possible," says Patterson. "At the end, we demonstrated 28,000 hours lifetime, with greater than 42,000 ignitions."

During normal operation, the cathodes operate at 2,000+ F. They emit up to tens of Amperes of electron current for periods as long as 18,000 hours, using propellant flow rates so small they are considered leak-rates for chemical engines.

Deep Space 2:

Mars Probe

Launch Date: January 1999

With Deep Space 2, NASA looks to uncover another piece in the life-on-Mars puzzle. The agency launched two small probes in middle January, housed in basketball-sized aeroshells. Once at Mars, the aeroshells will free fall onto the planet's surface at speeds of 400 mph, shattering upon impact. After this collision, the probes will borrow into the soil about three feet to measure the conductivity of the soil as well as take samples to determine if water a necessary element for life is present.

This mission tests the aerodynamic designed outer shell and mechanical packaging of the probes, says Li. This single-stage strategy, from atmospheric entry until impact with no parachutes or airbags to assist in the entry and landing is a first for NASA. Because the housings do not have an active attitude control system, engineers had to ensure the probes hit the surface at the right angle or they would never penetrate the soil. Designers positioned the microprobes in the nose of the aeroshell to keep the system's center-of-mass lower than its center of pressure. This forces the probes always to land "right side up," similar to a badminton birdie.

Space Technology 3:

Telescopes fly in formation

Launch Date: 2003

NASA will try to fly two spacecraft in formation using an optical interferometer, says Li. After the craft are "locked" together, the flying interferometer allows them to use star light to measure and adjust the distance between them within several nanometers. The spacecraft will contain telescopes and other instruments. Because the two ships will be flying so accurately together, they will act as one telescope system by combining the incoming light gathered from a single star.

Once validated, the technology can be used for flying autonomous vehicles at a precision of less than 1 nm, says Li. This will be particularly useful as a planet finder where spacecraft, flying in formation, will look for earth-like planets in neighboring solar systems to identify potential habitable environments. NASA plans to launch this mission after 2010, says Li.

In addition to technology, NASA is also gaining insight into this type of endeavor. "One of the lessons we've learned," says Cramer, is that these missions are more risky than we imagined. Risk is inherent in all technology development and in the interaction between the technology and its implementation." NASA hopes that by making its resources available for these new experiments, it will open the door and help take some of the risk out of further development and commercial application. Li says, that NASA sees these projects as building bridges between novel, untested technology, and commercial applications. "We hope to accelerate technology fusion by taking the risk out."

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.