This Week in Engineering explores the latest in engineering from academia, government and industry.
Episode Summary:
For the first time in half a century, NASA is preparing to launch a moon rocket. After multiple delays and redesigns, the giant Artemis 1 vehicle has rolled to the launch pad for the first in a series of final rehearsals for an unmanned Orion spacecraft mission around the moon. The combination of the Space Launch System and Orion spacecraft has been in development since the end of the space shuttle program and shares several key technologies with the earlier vehicle, including main engines, airframe structures and segmented solid rocket boosters.
The use of proven design elements in the Artemis program is hoped to grant the system capabilities that exceed the Apollo program’s Saturn 5 launch vehicle, with better reliability and lower relative costs. And there is another similarity to the 1960s: a space race. The race today is with Elon Musk’s SpaceX, whose giant Starship is already on the launch pad undergoing tests. A firm launch date has not been set for either vehicle, although it is generally expected that Starship will likely launch first.
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Transcript of this week’s show:
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A gigantic space vehicle crawls slowly out of the Kennedy Space Centre Vertical Assembly Building for the long ride to the launch pad. The spacecraft on top will travel to the moon and back.
50 years ago, this would have been Apollo. Now, the scene has been repeated this week by NASA with the rollout of the vehicle for the first flight of the Artemis program. The ground infrastructure—from the VAB, the Crawler Transporter and Pad 39B—are all legacies of the Apollo program, but the hardware for Artemis is definitely new.
The launch vehicle is the Space Launch System (SLS), which when combined with the Orion spacecraft stands 322 feet tall and weighs 5 ¾ million pounds. The system produces 8.8 million pounds of thrust, 15 percent more than Apollo’s Saturn 5. The basic SLS platform will be integrated with additional upper stages and a different spacecraft and payload fairing configurations to accommodate crewed missions to the Moon or deep space, as well as interplanetary robotic missions.
This week’s pad rollout is significant because the upcoming wet dress rehearsal will include propellant tank chill down and loading, a complete launch countdown and a practice recycle of the countdown clock in case of a hold. Propellant drain procedures will also be tested. After the wet mock, the vehicle will be carried back to the vertical assembly building where test sensors will be removed, batteries will be charged, late load cargo will be loaded and final checkouts will be performed prior to launch.
NASA has a great deal riding on the space launch system and the Orion spacecraft it carries. The SLS is the key, and unlike Apollo’s Saturn 5, the engineering of this more capable rocket includes a considerable amount of hardware proven from the Space Shuttle program. The most important, of course, is propulsion, and the four Aerojet Rocketdyne RS-25 core stage main engines are upgraded versions of Space Shuttle main engines. The current inventory of 16 Space Shuttle engines will be upgraded with new engine controllers, nozzle insulation and other changes to support a 512,000 pound thrust rating.
In the SLS application, they will be expended after launch and Aerojet Rocketdyne has restarted RS-25 production to support the program and reduce unit cost. Like the Space Shuttle, the system uses two strap-on solid rocket boosters, which will provide over 75 percent of vehicle thrust during the first two minutes of powered flight. The prime contractor for SRBs , Northrop Grumman, has added a fifth propellant segment to the Space Shuttle design, as well as new avionics, a different propellant grain profile and has illuminated the recovery parachute system, as SLS solid rockets will be expended.
For the upcoming Artemis 1 mission, the upper stage will be the United Launch Alliance Interim Cryogenic Propulsion Stage, derived from Delta 4 hardware and powered by another legacy liquid hydrogen oxygen motor, the RL10. 24,750 pounds of thrust will carry the Orion spacecraft beyond the moon, then back to Earth.
The Artemis program uses very different hardware from Apollo, and from an engineering perspective, the most major difference is not in propulsion systems or propellants or guidance, but in program objectives and management. In inflation-adjusted dollars, Saturn 5 cost just under $50 billion, with a cost per launch of 1 ¼ billion dollars adjusted to 2021. Current dollar estimated cost per launch for SLS are between two and four billion dollars, but despite much-criticized cost overruns and delays to SLS hardware development, the inflation-adjusted cost of the space launch system is approximately $23 billion, half the cost of Saturn 5 and with more capability.
Why? Extensive use of legacy technology, plus advances in computer-aided simulation, design and manufacturing, combined with modern PLM/ERP systems. Plus, the one factor that did not exist in the 1960s: competition. Not from Russia, but from Elon Musk’s SpaceX, where just down the beach from pad 39B, the SpaceX Starship vehicle is undergoing tests for spaceflight which, if successful, will rival the SLS for payload lift capability, and may do so at a lower cost per launch.
