Micro Spacecraft to Pave the Way for Future Space Exploration
Years ago, space visionaries dreamt that swarms of small spacecraft someday would travel to other worlds to explore them in preparation for future landings by human beings. Science fiction authors have written scripts and countless stories that outline how spaceship crews could send small 'probes' to alien worlds to scout conditions on those planets.
These visions are about to advance one step closer to reality because of the efforts of NASA and a nonprofit partner, The Aerospace Corporation, El Segundo, Calif., that are preparing to launch a 'micro spacecraft' to flight test it as early as 2006.
Image right: A diagram of the Reentry Breakup Recorder, also known as the Black box. Image courtesy: The Aerospace Corporation.
NASA and its partner recently agreed to develop the first 'black box' for spacecraft and test a prototype of this device that will be based on technology that Aerospace has been working on for several years. The 'black box' is actually a very small 'micro spacecraft' that would be attached to larger space vehicles. A joint program between NASA and Aerospace will develop the black box micro spacecraft, among many other low-cost, miniature space systems, under the terms of a NASA-Aerospace agreement.
Black boxes aboard aircraft record airplane data such as speed, altitude and crew conversations. After an accident, this information can be recovered to help investigators learn the cause of the mishap. The black box often includes a beacon that helps investigators locate the downed aircraft.
New, lightweight, low-cost devices the partners plan to develop would allow NASA and The Aerospace Corporation to flight test miniature sensor systems to gather temperature, pressure and other data, or to validate thermal protection systems for human missions.
The micro spacecraft capabilities and supporting technologies, scientists say, will help enable the President's Vision
to send human beings back to the moon and later venture on to Mars. These technologies and "foundation" research will make possible "sustained and affordable human and robotic missions," according to the researchers.
NASA hopes to put human beings back on the moon by approximately 2015. The agency also believes that human missions to Mars may take place as early as 2025.
"Micro spacecraft that can collect space flight data and return it to Earth will enhance space travel reliability through better designs," said G. Scott Hubbard, director of NASA Ames Research Center, located in California's Silicon Valley, who recently signed an agreement with William F. Ballhaus Jr., Aerospace president and chief executive officer, to develop the black box.
Image left: G. Scott Hubbard, director of NASA Ames Research Center, Moffett Field, and Dr. Bill Ballhaus, president and chief executive officer of the Aerospace Corporation, El Segundo,, Calif., are pictured shaking hands. Image courtesy: The Aerospace Corporation.
Micro spacecraft can test heat shields designed to protect future spaceships and their astronaut passengers from the extreme temperatures that space vehicles experience during high-speed flight when entering a planet's atmosphere.
As a micro spacecraft traveling at very high speed, enters a planet's atmosphere, friction causes intense heat to buildup on the shield. Part of the shield burns away, taking hot gases with it. If it is functioning correctly, the shield protects the spacecraft from incineration. Data that scientists gather from micro spacecraft during their descent into planets' atmospheres will help engineers validate existing heat shield designs. According to experts, these data also will assist engineers to develop new and more efficient designs.
"People had not figured how to put black boxes on spacecraft before because the boxes would tend to burn up during re-entry," said Dan Rasky, a scientist at NASA Ames. Ames is contributing its expertise in spacecraft heat shield design to the development effort.
"One of the first uses we see is using these space black boxes on the Crew Exploration Vehicle (CEV)," Rasky explained. The CEV is a future spaceship that NASA plans to use to fly people to the moon and beyond. Small spacecraft would ride piggyback on the CEV and other missions.
When the CEV ventures to the moon, scientists foresee micro spacecraft serving as lunar landing scouts, sent ahead of a CEV lunar landing module. According to researchers, micro spacecraft also would aid human missions to the red planet by monitoring the martian atmosphere and ground conditions, and providing general reconnaissance and landing beacons. The tiny spacecraft would also include chemical and biological sensors, useful in detection of substances related to potential past and present life on Mars.
Scientists additionally envision using micro spacecraft to do systematic studies of Mars, and sample returns from the moon, Mercury and Venus. Micro spacecraft may also conduct "on location" studies of Venus. Because they can be less expensive than other, more complicated spacecraft, a great number of micro probes could be sent to many more places in the solar system to gather data, researchers suggest. The gas giant planets of Jupiter, Saturn, Uranus and Neptune offer countless opportunities for micro spacecraft to study 'volatiles' - water vapor, ammonia, various isotopes and winds.
The basis for the effort to develop low-cost spacecraft technologies is the Reentry Breakup Recorder (REBR), a one-foot (0.3-meter) diameter, 2.2-pound (one-kilogram) device that will have a heat shield, batteries, data recorder, sensors and a transmitter. REBR has been under development at Aerospace for the past several years -- with NASA Ames being responsible for design of the micro spacecraft's entry system.
Image right: Model of the Reentry Breakup Recorder (spacecraft 'black box') to scale. The addition of the heat shield is expected to bring its size closer to 1 foot (0.3 meters) in diameter. Image courtesy: The Aerospace Corporation.
During initial flight tests, a prototype REBR will separate from a rocket or larger spacecraft due to aerodynamic heating and forces. Engineers designed REBR to collect data as the spacecraft to which REBR is attached re-enters the atmosphere and breaks apart. During the low-speed portion of the re-entry, REBR would 'phone home' to relay data by satellite prior to impact.
"Aerospace would use these devices to gather data during the re-entry and breakup of space hardware to validate and calibrate models, and NASA Ames would use them to test new heat shield materials and sensors," said Ethiraj Venkatapathy, planetary exploration technology manager at NASA Ames. The NASA-Aerospace team is using nanotechnology to develop very small, inexpensive sensors, he added.
Nanotechnology is the creation of materials, devices and systems based on a nanometer scale. A nanometer is one-billionth of a meter, roughly 10,000 times smaller than the width of a human hair. "Nanotechnology could lead to changes in almost everything from computers and medicine to automobiles and spacecraft," said James Arnold, a scientist with the NASA Ames Center for Nanotechnology.
Nanotechnology is already enabling engineers to make space science instruments smaller than before. An example is a miniature x-ray instrument within a device that scientists designed to measure the chemistry and crystallography of the surface of Mars during the upcoming Mars Smart Lander (MSL) mission.
Scientists say nanotechnology has resulted in nanoelectronics more fault-tolerant to radiation damage than present electronics. Nanoelectronics is electronics created on the nanometer scale. Spacecraft are susceptible to the effects of higher radiation levels because space vehicles fly beyond Earth's protective atmospheric layer.
Another technology scientists and engineers are using to develop micro spacecraft is a NASA Ames artificial intelligence (AI) computer program that can automatically design small spacecraft antennas, among other components.
The AI software - working on a network of personal computers - has already designed an antenna intended to orbit Earth while attached to a satellite.
The antenna, able to fit into a one-inch space (2.5 by 2.5 centimeters), can receive commands and send data to Earth from the Space Technology 5 (ST5) satellites. The three satellites - each no bigger than an average TV set - will help scientists study magnetic fields in Earth's magnetosphere. NASA scientists have spent two years developing the evolutionary AI software that designed the antenna.
"The AI software examined millions of potential antenna designs before settling on a final one," said project lead Jason Lohn, a scientist at NASA Ames. "Through a process patterned after Darwin's 'survival of the fittest,' the strongest designs survive and the less capable do not."
Image left: Black box diagram. Image courtesy: The Aerospace Corporation.
The software started with random antenna designs and through the evolutionary process, refined them. The computer system took about 10 hours to complete the initial antenna design process. "We told the computer program what performance the antenna should have, and the computer simulated evolution, keeping the best antenna designs that approached what we asked for. Eventually, it zeroed in on something that met the desired specifications for the mission," Lohn said.
"Not only can the software work fast, but it can adapt existing designs quickly to meet changing mission requirements," he said. Following the first design of the ST5 satellite antenna, NASA Ames scientists used the software to 're-invent' the antenna design in less than a month to meet new specifications - a very quick turn-around in the space hardware redesign process.
Evolved space antennas designed by Lohn's evolutionary software are 97 percent efficient as compared to conventional antennas that are only 38 percent efficient, according to scientists.
Scientists also can use the evolutionary AI software to invent and create new structures, computer chips and even machines, according to Lohn. "We are now using the software to design tiny microscopic machines, including gyroscopes, for spaceflight navigation," he ventured.
"The initial focus of the (micro spacecraft) collaboration (between NASA Ames and Aerospace) will be on development of small re-entry probes," said William Ailor, director of the Center for Orbital and Re-entry Debris Studies at The Aerospace Corporation and Aerospace lead for the effort.
"Similar technologies could be used on an Ames concept called Scout Probes for Exploration," Rasky said. This concept makes use of small entry probes to gather information and reconnaissance on atmospheric and surface conditions and hazards, according to Rasky.
Development and flight-testing of very small entry probes that contain nanosensors also will help NASA considerably reduce the cost of its planetary robotic and human exploration missions, according to Venkatapathy.
Researchers say that NASA has completed most of the "easy" missions to planets and moons. The completed remote observation orbiters and fly-by missions have whetted scientific interest for even more exotic exploration to gather extensive data on the surfaces of alien worlds. The ultimate goals of more ambitious deep space missions include 'on-the-scene' science and surface exploration.
Scientists hope to use micro spacecraft to scout alien worlds to reduce some of the risk to human beings and robots. This risk is related to a larger spacecraft's entry and descent into planetary atmospheres, and landings on moons and planets.
NASA Ames has much experience in the development of small space probes. In 1971, Ames used a 137-pound (62.1-kilogram) spacecraft, the Planetary Atmospheric Experiment Test vehicle, to study spacecraft heating and entry into Earth's atmosphere.
Ames also proposed the Mars Environmental Survey, a multi-lander network to study the fourth planet. This proposal evolved into the Mars Pathfinder mission. The Deep Space-II mission, which flew 'piggy back' on the Mars 98 Lander, contained critical entry systems technology from Ames.
In the future, once they are tested on Earth, NASA will be able to send Trailblazer micro-probes, each weighing two - 22 pounds (one - 10 kilograms) to places like Mars, gas giant planets like Jupiter, Saturn and Neptune and to a moon of Saturn called Titan, according to Venkatapathy. The probes will measure atmospheric and surface conditions and help scientists evaluate potential dangers, he explained.
"These probes also could serve as landing beacons for following piloted or robotic vehicles. Scout probes for exploration could be a critical, new capability for reducing risks encountered with remote exploration landings," Rasky predicted.
Publication-size images can be found at:
NASA Ames Research Center, Moffett Field, Calif.