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| Orion Command Module Approaches International Space Station Courtesy Lockheed Martin |
The following article was originally printed in the March 2008 issue of Colorado Country Life Magazine, and it's interesting to see where we are along the timeline now that nearly four years have passed since I interviewed Lockheed Martin's chief engineer for the project. Enjoy the story!
Colorado is Helping to Put America (Safely) Back on the Moon By: Reggie Paulk
The last people to walk on the Moon were American astronauts Eugene Cernan and Harrison “Jack” Schmitt during Apollo 17. As part of a lunar mission that lasted nearly 75 hours, the pair spent over 22 hours walking and driving around their landing site collecting lunar samples they would take with them on their return to Earth.
Cernan and Schmitt landed on the Moon on December 11, 1972. Three days later, they blasted off toward the Command Module, and we haven’t been back since. It’s strange to think that a large section of the population today has never witnessed an actual Moon landing. Beginning as early as 2018, we’re going back, and Colorado is at the epicenter of our return.
The Space Shuttle has lost its luster. It was never designed to go anywhere but into Earth orbit. While the concept of its reusable design seemed revolutionary at the time, the enormous complexities of the machine have made it prohibitively expensive to operate. Finally, the Challenger and Columbia disasters highlighted major safety issues with the program. Eventually, NASA decided to go back to the drawing board and design a space ship for the next generation of explorers.
A lot has happened in the 35 years since the end of the Apollo program. Technology has given birth to amazing new capabilities, and it seems appropriate to use those capabilities in order to explore our solar system. Using the knowledge gained from the Apollo and Shuttle programs, NASA is designing a space system that maximizes both safety and launch capability, while providing a springboard for Moon exploration and beyond. The system, dubbed Constellation, consists of the Ares I and V launch vehicles, and the Orion Crew Exploration Vehicle, or CEV.
Anyone familiar with the Apollo and Shuttle programs will see familiar shapes when they gaze upon the cone-shaped Orion spacecraft; it borrows heavily from the Apollo and Shuttle programs. The Orion spacecraft and Ares I booster look like a mix of the Space Shuttle’s solid rocket booster below a smaller version of the external fuel tank with a large Apollo capsule at the top. And that’s almost exactly what it is. The main booster is an adaptation of the Shuttle’s existing reusable solid rocket boosters, with an extra segment of fuel for a longer burn. The second stage is a liquid-hydrogen and oxygen fuel tank powered by a J-2X engine adapted from the Apollo era J-2 engine that powered the Saturn V rockets. Finally, the CEV’s service module uses a slightly modified Space Shuttle Orbital Maneuvering Engine or OME.
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| Orion Command Module Photo Courtesy Lockheed Martin |
In order to learn more about Orion, we interviewed Bill Johns of Lockheed Martin in Denver. As Orion’s chief engineer, Johns has the awesome responsibility of overseeing a highly complex and intricate design process that will one day culminate in a return to the Moon. Because Orion is the manned element of the Constellation program, astronaut safety is the main consideration for almost all of the spacecraft’s design. This focus is evident when speaking with Johns.
Describing the Space Shuttle, Johns discusses its limited capabilities, “When the Shuttle was new, NASA thought it was going to be a semi-truck type delivery system. Had it been cost-effective, it really would have been the way to get payloads into orbit. Unfortunately, it didn’t pan out to be cost-effective. As a result of Challenger, they decided that the Shuttle is certainly not a safe way to put humans into space. It may well be the most complex spacecraft ever built—it’s phenomenally complex. The neat thing about Orion is that Ares V will carry up all the ‘stuff.’ The Ares I will carry up just the people. That is fundamental to what went into what NASA called their exploration system architecture study.”
That complexity is the Shuttle’s Achilles heal. There are just too many things that can go wrong to jeopardize flight safety.
Johns continues, “The Space Shuttle has always had a very limited abort capability. Rule number one on this program is you’re going to make sure that between the launch abort system and various service module aborts, there are to be no black zones. From the launch pad to orbit, we will be able to bring Orion back safely.”
Like Apollo, Orion will be equipped with a launch abort system comprised of solid rocket motors at the very tip of the spacecraft. The sole purpose of the launch abort system is to carry the CEV away from the rest of the rocket so that it may deploy its parachutes and land the crew safely on land or water. One problem faced by the engineers of Orion is that the abort system has to be able to work on the launch pad or at 300,000 feet. These different scenarios make for some interesting engineering challenges.
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| Computer Image Of Orion Launch Abort System Photo Courtesy Lockheed Martin |
“An abort off the launch pad is extremely painful,” says Johns, “You will take off at 15 to 18 times the force of gravity (g’s). The check is, is that survivable by the crew? The abort motor’s thrust tails off after two seconds, and after five seconds, there’s nothing coming out. The bulk of the propellant is burned after 3.5 seconds, and it’s tailing off quickly.”
During a launch pad abort, a 200-pound astronaut subjected to 15 times the force of gravity will weigh 3000 pounds—the equivalent of most small cars! Although very uncomfortable, it’s survivable; aerobatic pilots regularly experience up to 13 g’s during a performance. But even more amazing is everything that has to happen to make a safe pad abort.
Johns describes what happens, “For a pad abort, you’re only going a mile high, so the sooner you can get the ‘chutes coming out, the better off you’ll be. Now it’s a race against time because you need to get the chute out that’s going to pull the forward bay cover off, then the drogue ‘chutes come out and pull out the mains so you can make a safe landing.”
Think about it… The abort rocket fires for less than five seconds, carrying the CEV over five thousand feet above the launch pad. A car moving along the highway at 60 miles an hour covers a mile every minute; traveling from zero to a mile in five seconds is definitely going to be a hard acceleration—which explains the 15 to 18 g’s.
To reach orbit, Orion will accelerate to over 17,000 miles per hour—4.7 miles per second--to rendezvous with the Space Station. At any time after launch, it may be necessary abort, and that is where the tremendous power of the abort rocket comes into play. On the launch pad, everything is sitting still. There’s no drag from air moving over the spacecraft. At 80,000 feet, the spacecraft will be moving much faster than the speed of sound. This presents a massive amount of drag from air friction that must be overcome by the abort motor in order to pull the spacecraft away from the booster. Think of the effort it takes to wave your arm quickly while standing in a room. Now, imagine doing the same thing while standing in the back of a truck going down the freeway at 100 miles per hour—waving your hand into the air stream will take considerably more effort. The measure for the highest amount of force the air exerts on the spacecraft during a launch is called maximum aerodynamic pressure. Maximum aerodynamic pressure determines how much thrust the abort motor must exert.
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| Orion Command Module Atop The Ares I Rocket Photo Courtesy Lockheed Martin |
“When the spacecraft is moving through maximum aerodynamic pressure,” Johns says, “the first 300,000 pounds of thrust is just to overcome the drag. The rest is now to accelerate away [from the booster]. So at maximum aerodynamic pressure, the acceleration is only about 2 g’s higher than the normal 3 g acceleration of a normal launch.”
It’s obvious that an abort after the spacecraft has gained a little speed is better than the neck-snapping scenario of a ground abort, because the abort motor is overcoming drag instead of accelerating the CEV to a safe altitude.
The final abort scenario comes after the spacecraft is above the majority of the atmosphere, where there is little or no air resistance on the spacecraft. This is where the technology of the 21st century comes into play.
Johns describes the abort system as consisting of three motors: The abort motor, the jettison motor, and the attitude control motor. The attitude control motor has eight different ports, and an ingenious device that allows it to steer the spacecraft during an abort scenario.
“Why would you need to steer?” asks Johns. “Well, Apollo did a tremendous amount of work and had a phenomenal system, but they identified late in the program some potential shortcomings of their launch escape system. For the high altitude abort, you don’t have aerodynamics to help you go from pointy end forward to heat shield forward. Apollo had a canard system, which we have as well, where you throw out these wings at the front end of the launch abort system that flip you heat shield forward. (Like the feathers stabilize a dart.) Our launch abort system, not unlike Apollo, has to be able to pull the crew away at close to 300,000 feet. High altitude aborts don’t allow the canards to work because of the lack of air, so the capsule would tumble until reaching a lower altitude where the air would interact with the canards. But the dynamics on the crew in the several minutes until you get to that point aren’t going to be good. The attitude control motor, for high altitude aborts, flips the module around and stabilizes the capsule heat shield forward. Now you’re just like you are during re-entry. You can turn on your attitude control system, and it’s just like you’re coming back from space. A lot of that has to be computerized. It’s borrowed from ejection seat technology.”
NASA is retiring the Space Shuttle in 2010, and Orion will begin test flights the following year. The first manned missions will take Orion to the International Space Station around 2014, with plans to continue to the Moon by 2018. Blending modern technologies with proven ones is a recipe that will hopefully lead to an exciting and highly successful future in space for the United States. With nearly 600 employees in Colorado dedicated to the Orion program, Lockheed Martin is safely leading the way back to the Moon and beyond.
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