Satellites Rovers, and Robots: NASA Langley's Uncrewed Space Exploration and Science

SATELLITES, ROVERS, AND ROBOTS:

NASA Langley’s Uncrewed Space Exploration and Science

By Craig Collins

In the early years of the new National Aeronautics and Space Administration (NASA), as the new Space Task Group at Langley Research Center was figuring out how to send men into space, existing space programs at Langley continued to hum along. In their explorations of the operational limits of aircraft, Langley researchers, who had been firing rockets since 1945 from a launch site on nearby Wallops Island, Virginia, had already begun approaching the conditions of spaceflight. After NASA was formed, Wallops became the site for uncrewed tests of the first American spacecraft, the Mercury capsule. On Dec. 4, 1959, the rhesus monkey Sam was boosted into orbit from Wallops, in a successful evaluation of the capsule and escape system known as the Little Joe.

Meanwhile, Langley researchers were neck-deep in two other in-house projects. Since 1956, a team had been at work on an idea hatched by aeronautical engineer William O’Sullivan: Project Echo, which would become the world’s first communications satellite.

Echo took a while to achieve success, in part because it presented Langley researchers with a seemingly impossible trade-off. It would be a “passive” communications satellite – signals would not be sent from the satellite, but literally bounced off its surface and deflected to another Earthly location – and so would have to be fairly large. At the same time, it would have to be feather-light, in order to ride aboard the rockets of the day. O’Sullivan solved this apparent paradox by envisioning a metallic balloon.

Langley historian James Hansen, in his history of Langley’s space research, Spaceflight Revolution, called the Echo balloon … perhaps the most beautiful object ever to be put into space. The big and brilliant sphere had a 31,416-square foot surface of Mylar plastic covered smoothly with a mere 4 pounds of vapor-deposited aluminum. All told, counting 30 pounds of inflating chemicals and two 11-ounce, 3/8-inch-thick radio tracking beacons (packed with 70 solar cells and 5 storage batteries), the sphere weighed only 132 pounds. After some trials and errors, the Langley team figured out a way to fold this 100-foot sphere into a cylindrical mass that could be packed into a 26-inch canister. The first successful launch of Echo, now known as Echo 1, took off from Cape Canaveral on Aug. 12, 1960. Once ejected from the canister in space, powdered chemicals, packed inside Echo’s skin, slowly vaporized into gas as they absorbed heat from the sun, inflating the satellite balloon, or “satelloon,” to its full 10-story height, clearly visible to the naked eye as it crossed the night sky. From its orbit, 1,000 miles above the Earth, Echo 1 bounced a message from President Dwight D. Eisenhower back to the world: This is President Eisenhower speaking. This is one more significant step in the United States’ program of space research and exploration being carried forward for peaceful purposes. The satellite balloon, which has reflected these words, may be used freely by any nation for similar experiments in its own interest. Langley’s engineers estimated that Echo would survive about two years, but it orbited the Earth until May 1968. Echo 2, about one-third larger than Echo 1, was launched in January 1964 and orbited until June 7, 1969, about six weeks before Neil Armstrong and Buzz Aldrin took their first steps on the Moon.

This low-angle self-portrait of NASA’s Curiosity Mars rover shows the vehicle at the site from which it reached down to drill into a rock target called “Buckskin” on lower Mount Sharp. Langley Research Center has played an important role in NASA uncrewed missions since the launch of the nation’s first satellites.

NASA Photo

The Echo design was later used in the fabrication of NASA’s PAGEOS (Passive Geodetic Earth Orbiting Satellite), a sphere the same size as Echo 1, launched in 1966. Used to help form a worldwide satellite triangulation network, PAGEOS began to break apart in 1975.

Another major program to be carried out entirely by Langley researchers was the Scout rocket, begun in 1957. Designed as an inexpensive rocket to carry small research payloads, the Scout, while much smaller than the Redstone and Atlas vehicles used for the Mercury missions, was by far the largest rocket to launch from Wallops Island – a four-stage, solid-fuel booster capable of placing a 150-pound satellite into orbit 500 miles above Earth.

On Feb. 16, 1961, Langley’s Scout rocket became the first solid-fuel rocket – and the first rocket from Wallops – to place a payload in orbit: Explorer 9, a 12-foot inflatable satellite designed to study the density and composition of the upper atmosphere. Explorer 9 remained in orbit for more than three years.

Echo I was the world’s first communications satellite, or “satelloon,” a giant inflatable sphere from which signals could be bounced.

NASA Photo

To the Moon

When President John F. Kennedy issued his famous 1961 challenge to land men on the Moon, Langley researchers, who’d already begun examining the problems associated with lunar exploration, weren’t as stunned as the rest of the country – but even they were shocked by the president’s deadline. He’d asked the nation to commit itself to a Moon landing “before this decade is out” – before New Year’s Day 1970.

The main problem with sending people to the Moon within nine years was that nobody knew much about the Moon yet. Some of science’s leading minds hypothesized that its surface was covered in a layer of dust so thick it would swallow any craft that tried to land on it. In Spaceflight Revolution, Hansen recounted the theory of one esteemed Ivy League astronomer: “ … the Moon could even be composed of spongy, fairycastle-like material that would crumble upon impact.”

In 1963, NASA decided on a separate program designed explicitly to serve the needs of the Apollo mission: to launch a series of orbiting spacecraft that would provide high-resolution stereoscopic photographs of the lunar surface and help Apollo’s people decide where the astronauts would land. Because the Jet Propulsion Laboratory (JPL), NASA’s robotic spacecraft experts, had their hands full with Ranger and Surveyor – two projects to learn more about the lunar surface – NASA leadership turned to Langley Research Center, whose researchers had demonstrated in the early years of the Mercury program a gift for project management.

The first image of Earth taken from space, from Lunar Orbiter 1 as it orbited the Moon. The original Lunar Orbiter image has been enhanced with new technology.

NASA Photos

A lot was riding on the Lunar Orbiter program, and not everyone thought it was a good idea to assign it to Langley. Nobel Prize-winning chemist Harold Urey sent a strongly worded letter to NASA Administrator James Webb: “How in the world,” he wrote, “could the Langley Research Center, which is nothing more than a bunch of plumbers, manage this scientific program to the Moon?”

Langley managed NASA’s Lunar Orbiter Program. Between 1966 -1967, five orbiters built by The Boeing Company were launched, and 99 percent of the Moon was photographed. The Orbiter spacecraft is depicted in this NASA graphic.

NASA Photos

Walt Engelund, Langley’s Director of the Space Technology and Exploration Directorate, put this comment into historical context: “At the time,” he said, “Langley was viewed as a bunch of people who worked in wind tunnels and built structures, but were not sophisticated builders or purveyors of spacecraft.”

Viking 1 launched aboard a Titan rocket Aug. 20, 1975, and arrived at Mars on June 19, 1976. The first month was spent in orbit around Mars, and on July 20, 1976, Viking Lander 1 separated from the Orbiter and touched down at Chryse Planitia.

Photo Courtesy of NASA

Lunar Orbiter would become one of Langley’s most successful programs, however. Five orbiters were launched within a year, each of them successfully, between August 1966 and 1967. The spacecraft returned photography of 99 percent of the Moon’s surface, both the near and far side, with resolution down to 1 meter. These high-resolution images made it possible to select the best landing sites for both the Surveyor and Apollo spacecraft – including Apollo 11’s Tranquility Base – and radiation experiments on the orbiters helped to confirm the Apollo spacecraft’s design would protect astronauts from solar radiation during their journey.

May 1, 1974: Viking under assembly at Martin Marietta Aerospace near Denver, Colorado. Martin Marietta was prime and integration contractor for the Viking project, which Langley led.

Photo Courtesy of NASA

Images of the Moon seem routine now, but the pictures sent back by the Lunar Orbiter spacecraft were awe-inspiring. On Aug. 23, 1966, Lunar Orbiter 1 captured the very first “earthrise” picture, an image of Earth from above the Moon, and on Aug. 8, 1967, Lunar Orbiter 5 relayed the first full picture of the entire Earth.

Viking: A Second Triumph for the Plumbers

In the 1960s, five successful missions in five attempts was an unusually successful record for uncrewed space exploration. Lunar Orbiter’s perfect record in reaching the Moon, a quarter of a million miles away, led NASA’s Office of Space Science to believe Langley’s project managers should take charge of a program – Project Viking – to send uncrewed landers on a journey of more than 400 million miles, to Mars. Viking, the first operational spacecraft to land on another planet, would then deploy experiments designed to detect signs of life on the Martian surface. In 1968, Langley’s James Martin, who had been assistant manager for the Lunar Orbiter program, was chosen to lead the new mission to Mars.

Project Viking would consist of two identical spacecraft, Viking 1 and Viking 2, each consisting of an orbiter and lander that together weighed more than 3 tons. The orbiter and the lander would travel to Mars together, and remain in orbit while the orbiter scanned the Martian surface for a suitable landing site. When the lander – a 5-footwide platform supporting scientific instruments – departed for the Martian surface, the orbiter would act as communications relay while performing its own scientific experiments.

The Langley team chose Martin Marietta (now Lockheed Martin) as the principal contractor for Project Viking, and the company built and tested two Langley-designed landers at its facility near Denver. The JPL designed and built the Viking orbiters – and would later manage the science mission – while Lewis (now Glenn) Research Center designed the launch vehicle, a Titan III-E/ Centaur rocket. Other NASA centers, including Ames, Goddard, the Kennedy Launch Complex, and the Johnson Space Flight Center, would also contribute to the program, which was planned to achieve its mission on the U.S. bicentennial: July 4, 1976.

Taken by the Viking 1 lander shortly after it touched down on Mars, this image is the first photograph ever taken from the surface of Mars. It was taken on July 20, 1976. The primary objectives of the Viking mission, which was composed of two spacecraft, were to obtain high-resolution images of the Martian surface, characterize the structure and composition of the atmosphere and surface, and search for evidence of life on Mars.

Photo Courtesy of NASA

Both Viking 1 and Viking 2 were launched in the summer of 1975. For each, the journey took 11 months; Viking 1 entered Mars orbit on June 19, 1976 and Viking 2 followed on Aug. 7. The Viking 1 Lander wasn’t able to touch down by July 4, because the orbiter’s images showed the intended landing site was too rocky and dangerous. On July 20 – seven years to the day after Neil Armstrong and Buzz Aldrin had first set foot on the Moon – Lander 1 detached from its orbiter and plunged into the Martian atmosphere at nearly 10,000 mph. At about 4,000 feet, a parachute deployed and retrorockets fired, slowing the lander’s descent to about 6 mph.

Lander 1 came to rest on an ancient floodplain known as Chryse Planitia. Lander 2 set down about 1,000 miles closer to Mars’ north pole, in the Utopia Planitia, on Sept. 3. The landers, which had analyzed the Martian atmosphere during their descents, promptly began scooping up and analyzing Martian soil samples, which revealed strange and unexpected chemical activity – but no definitive signs of life.

The heat shield for NASA’s Mars Science Laboratory (MSL) is the largest ever built for a planetary mission. In April 2011, technicians at Lockheed Martin Space Systems in Denver install electronics for the Mars Science Laboratory Entry, Descent and Landing Instrument (MEDLI). Developed by Langley in partnership with NASA’s Ames Research Center, the instrument collected data about temperature and pressure during MSL’s descent through the Martian atmosphere. Langley has special expertise in developing and providing technologies to support the entry/ descent/landing (EDL) stages of uncrewed missions.

Photo Courtesy of NASA

Both Viking orbiter/lander sets performed far past their expected service lives. The landers, designed to function for 90 days, continued to collect data for more than six years, until Lander 1 shut down on Nov. 13, 1982. In addition to the first measurements of the planet’s atmospheric composition, temperature, pressure, and density, and data on the Martian soil’s composition – from which life has not yet been ruled out by some of the scientists who’ve studied it – Project Viking sent back 55,000 photographs of the Martian surface from orbit and 5,500 pictures from the landers. Like the Lunar Orbiter’s first images of the Earth from a distance, those first color images, of the Martian surface and the planet’s pink sky probably don’t seem all that extraordinary to many Americans today, but they provide a window to a world that carries tremendous emotional – even spiritual – significance to those at NASA Langley who remember, or at least understand, what it took to get those pictures.

Langley’s expertise in entry, descent, and landing is why the center’s engineers are supporting NASA’s Space Technology Mission Directorate in the development of an inflatable spacecraft technology called the Hypersonic Inflatable Aerodynamic Decelerator – or HIAD for short. The inflatable orange rings work like a parachute, using the drag of a planet’s atmosphere to slow down a spacecraft, protecting it from the intense atmospheric heat, and also allowing it to have a softer landing. The HIAD could give NASA more options for future planetary missions, because it could allow spacecraft to carry larger, heavier scientific instruments and other tools for exploration.

Photo Courtesy of NASA

Langley’s Role Today

Much of Langley Research Center’s current work in uncrewed space exploration, said Walt Engelund, evolved from the expertise its researchers developed in the Lunar Orbiter and Viking missions. “One of the most important contributions we made to the development of Viking,” he said, “was the technology we developed for the entry/descent/landing system. That’s enabled us to contribute to all the Mars missions since, all the way up to Mars Science Laboratory in 2012 and the 2020 rover mission that’s coming.” When spacecraft enter the Mars atmosphere, which is about 1/100th as dense as Earth’s, without first entering orbit, they’re moving at much faster speeds than Viking – the Pathfinder lander, which descended in August 1997, had to slow from a speed of around Mach 40, about 30,000 miles per hour, to essentially zero miles per hour within minutes. The expertise gained in Project Viking has allowed Langley researchers to design the entry/ descent/landing (EDL) systems for such spacecraft: the aeroshell (the shielded shell that helps decelerate and protect a spacecraft vehicle from heat, pressure, and drag during atmospheric entry), retrorockets, and parachutes, as well as the computations and modeling that help determine optimal positioning, timing, angle of entry, and other important variables.

If something goes wrong with a mission to another celestial body, it will most likely go wrong during the EDL phase, which is why EDL teams spend years planning, and practicing millions of computer landings that account for every conceivable set of variables, for a process that takes several minutes. In 2023, the current plan is for NASA’s OSIRIS-Rex spacecraft, which launched from Cape Canaveral in September 2016, to return a sample from an asteroid, RQ36, safely to the ground at the Utah Test and Training Range near Salt Lake City. “The challenge with this asteroid sample return mission,” said Engelund, “is that you’re coming back to Earth at much faster speeds than any previous missions have ever flown. The aeroshell, the thermal protection system materials, and the entry, descent, and landing technologies that enable you to do that are critical. That’s been a big part of our research and focus the last two decades.”

For a number of reasons, Langley Research Center’s work in space has, for the past few decades, been organized around its core expertise – EDL technologies; in-space assembly and operations technologies; strong, lightweight materials; and deep space habitation systems, and big projects have tended to draw resources away from these core capabilities. “At some point after the Viking project,” said Engelund, “we decided we need to stop doing these big missions and let the JPLs and the Goddards and the JSCs do that work. We needed to focus on technology development for aeronautics and space.”

Langley chemists and engineers are on the leading edge of investigations into the next generation of materials and structures for space applications – helping to design and fabricate, with maximum efficiency, the most advanced and lightweight composites and metals. This work naturally feeds into Langley’s expertise in the design and construction of large space structures, which began with a series of studies, from the 1970s into the early 1990s, evaluating the assembly methods of astronauts in low Earth orbit.

Today, Langley researchers are involved in evaluations of autonomous robotic inspace assembly, particularly of structures composed of replaceable modular units. Langley engineers, for example, are working with a commercial communications satellite provider on more efficient ways of upgrading its broadband service. “The problem is packaging everything into a payload shroud,” Engelund said. The reflector antennas that beam signals to customers are necessarily large, but Langley engineers have figured out a way to send them into orbit in pieces, to be assembled robotically. “We’ve got a technology, and are working with them on a capability,” said Engelund, “to package additional – unassembled – antennas on top of the spacecraft. And once you get into orbit, you reach out with a robot arm and add additional antennas. Essentially, you double the bandwidth … It’s actually using a joining technology Langley developed back in the 1980s for space shuttle astronauts to go out and assemble structures in orbit.”

Langley’s successful track record in project management has made it a source of data and forecasting for NASA Headquarters. “We do a lot of mission concept studies for headquarters,” Engelund said, “and then headquarters tries to weigh those against budget priorities, and sometimes those things get funded, and sometimes not. But our main focus continues to be on developing technology. That has been, and continues to be, our real value proposition as we develop the concepts and enabling technologies for advanced robotic space flight missions – to Mars and maybe beyond.”