On today's episode, NASA’s Return to the Moon Accelerates.
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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.
Get your popcorn.
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