Orion will be the first crewed spacecraft designed to fly astronauts beyond low-Earth orbit in five decades. The demands of designing a deep space crewed spacecraft meant that Orion faced a great many challenges during its development that nobody had faced since Apollo. While the experience of those who designed and built Apollo remains in the form of flight articles at various NASA facilities, sadly many of those who created the Apollo spacecraft are gone, and with them their lessons learned. Persisting experience between generations has since the dawn of time been a perennial problem for civilizations.
So NASA had to learn as it designed and tested Orion, and do so without the bountiful budgets of the Apollo era. The operational and safety experience NASA gained from the Apollo through the Space Shuttle programs also informed the design of the Orion spacecraft. In particular, the heritage of Apollo is in plain view when looking at the Orion spacecraft; the outer mold-line of the Orion spacecraft is the same as; the parachute system of Orion, though bigger, is similar to, that of the Apollo command module. Yet, Orion is a more advanced crewed spacecraft able to carry crew of 4, not 3 as in Apollo, astronauts on a 21-day, not 14-day, mission.
One of the chief challenges of the Orion program, according to Ms. Debbie Korth, NASA’s Orion Crew and Service Module Manager, has been getting the spacecraft to its designed weight, a perennial problem for any spacecraft. According to NASA’s Johnson Space Center, the weight of the Orion system through various events of the mission are,
|CSM SC Adapter||Lift-off||1,125||510|
Weight of the Orion spacecraft matters for a number of reasons ranging from launch through landing. For launching, Orion can rely on the SLS. Even at SLS’s lowest payload mass capability of 167,551 lb (76MT) for the Block 1A, the SLS has more than enough power to launch Orion and a crew of four to the Moon. So, every pound saved by keeping the Orion CSM within its targeted weight means additional payload mass that can be delivered to orbit. But in the event of an abort, the capabilities of the Orion parachutes must not be exceeded by the weight of a fully fueled and loaded Orion crew module.
The Orion parachute system, more precisely its capsule parachute assembly system (CPAS), is similar to the Apollo Earth Landing System design1. CPAS is designed to weight 1,124 lbs (510 kg) and, like Apollo, is stored in the Orion Crew Module forward bay beneath a forward heat shield that is jettisoned during subsonic flight prior to parachute deployment. Like Apollo command module (CM), the Orion crew module (CM) employs three main parachutes to land astronauts safely on the ocean. The Orion main parachutes are like those of Apollo, but are the largest ever built for a spacecraft. And as in Apollo, Orion’s parachute system designed to enable just two main parachutes to safely land an Orion crew module either from low-altitude (pad abort) or high-altitude2. Although atmospheric reentry will initially slow the spacecraft from 20,000 mph (8,940 m/s) to 325 mph (145 m/s), the Orion main parachutes have the job of slowing down Orion to 20 mph (8.84 m/s) or less needed for a safe water landing. The design of the three Orion Kevlar/Nylon hybrid main parachutes resulted in each having a surface area 10,500 square feet, 116 feet diameter, and 310 lbs weight3.
The resulting size of the Orion parachutes motivated a revision of Orion’s exterior moldline because the diameter at the top of Orion would not have allowed for sufficient packaging room for the Orion parachute system. As a result, Orion’s nominal backshell angle was widened 2.5° to provide more packaging volume for the parachute system4.
Orion certainly benefited from the Apollo program’s parachute design and testing. During development of the Apollo command module parachute system in the early through mid-60’s, several Apollo CM boilerplate test articles were destroyed5. The lessons learned from that experience meant that, after ten years of testing, the Orion Capsule Parachute Assembly System (CPAS) experienced only one failure during the Crew Development Test 2, or CDT-2, that was conducted on August 20, 2008. And those on the parachute test program accurately point out that the one failure wasn’t on Orion’s Capsule Parachute Assembly System’s part, but of the CPAS Pallet Separation System (CPSS) that was to separate the Orion parachute test vehicle (PTV) from the CPAS pallet6. The subsequent tests, including the 24th, and final, test of the Orion CPAS conducted on September 12, 2018, were successful. Orion’s ultimate parachute test, EFT-1, occurred on December 4, 2014 when Orion re-entered the atmosphere at around 20,000 mph and landed safely.
One area where the Orion and Apollo spacecraft diverge is in personal space. The Orion spacecraft, at 314 cu.ft (8.89 cu.m), has more habitable volume than did Apollo at 210 cu.ft (5.95 cu.m). For each of the four astronauts, Orion’s 78.5 cu.ft (2.22 cu.m) per astronaut makes it a roomier spacecraft than was Apollo at 70 cuft (1.98 cu.m). The layout of the Orion CM’s interior is a clean, open architecture that consists of four seats and an instrument panel. The seats are arranged in two rows, one row for the commander and pilot and another for the mission specialists. Seated facing Orion’s instrument panel are the commander and pilot. Below, or in Orion’s coordinate system in the positive z-axis, the commander and pilot are the seats for the two mission specialists. According to Korth, which seat the commander and pilot will occupy has yet to be set in stone.
The design of the Orion occupant restraint system owes much to the Columbia disaster. The Columbia Accident Investigation found that the Shuttle occupant restraints, the seat and seatbelts, did a poor job of restraining the astronauts, although ultimately it wouldn’t have made a difference in averting the disaster. Both the Orion seats and seatbelts were designed to better maintain astronauts in their seats during dynamic events, say tumbling, while accommodating a large size range, from females at 4’10” to males up to 6’4”. A great deal of work was done in studying how difficult it was for astronauts to get into and out of their seats, or ingress and egress in NASA-speak7. After launch, each seat’s footrest can be quickly disconnected and stowed to make for easier movement about the spacecraft cabin.
The Orion instrument panel is, according to Korth, fully software driven, unlike Apollo. It consists of three large screens, translation controllers on each end, and a plethora of buttons, but still far fewer than the 2,000 switches and controls on the Space Shuttle or hundreds on Apollo. The screens are both the primary display and input-output. Debbie Korth pointed-out that on each of the commander’s and pilot’s armrests is a device that looks like a game controller and is the instrument panel’s mouse. Touch screens were eschewed in favor of a menu driven system actuated by buttons around each screen. The buttons on the instrument panel are not directly connected to instrumentation as in Apollo but instead activate software routine for their functionality. According to a ComputerWorld article8, the Orion instrument is built by Honeywell Int’l around the panel used on Boeing’s 787 jet airliner. There are two main flight computers that use two radiation hardened IBM PowerPC 750FX single-core processors, a CPU introduced in 2002 and used in Apple computers such as the iBook G3 until 2005. While the two CPU’s in each flight computer might be similar to the processor in the iBook G3 laptop, the rest of the flight computer bears little resemblance; the flight computers have been ruggedized for space travel with a larger housing, a thicker circuit board, and hardware to minimize vibrations. The two 750FX’s in each flight computer don’t error check each other but instead perform tasks and then compare their results. If the processors don’t get the same results, the flight computer will stop giving commands and reset itself, a process that takes 20 seconds, which is estimated to happen one-in-3.7 missions. If both main flight computers go down, a one-in-8,500 chance, there is a third flight computer that knows the state of the vehicle and acts as a source of truth for the Orion spacecraft’s state data at the time the flight computers return online. The chance of losing all three computers at the same time is one in 1,870,000 missions.
According to Orion CSM head Korth, for personal entertainment, astronauts will have tablets, with several spares in case radiation breaks some.
Speaking of radiation, one of the challenges of exploring beyond the relatively benign radiation environment of low-Earth orbit that is deep space is radiation9. The first study of deep space radiation occurred during NASA’s rover Couriosity’s trip to Mars using its Radiation Assessment Detector (RAD)10. Like an astronaut, RAD, which is a part of Curiosity’s instrumentation, sat deep inside the spacecraft transporting Curiosity to Mars. The results of the trip, revealed in 201311, indicate that solar and cosmic background radiation, caused by solar energetic particles (SEPs) and galactic cosmic rays (GCRs), are much more intense that previously thought. A 21 day trip to, orbiting, and returning from the Moon would be equivalent to 1.75 times the annual radiation allowed. With that in mind, NASA started looking for ways to protect astronauts within the Orion spacecraft. One solution was to minimize the time astronauts would be exposed to radiation by optimizing Orion trajectory12, which was also done during the Apollo program. Another step to protect astronauts was a collaboration between Lockheed Martin Space and StemRad Israel to develop the Radiation Vest for Astronauts, or AstrRad13 that uses proprietary smart shielding to protect the most vulnerable organs.
To better understand how radiation in deep space affects humans on Orion, in May 2018, NASA approved the Matroshka AstroRad Radiation Experiment (MARE) that will use two female CIRS ATOM Dosimetry verification phantom test articles14, Helga, weighing 79.1 lbs (35.88 kg), and Zohar, weighing 79.3 lbs (35.99 kg) to test the radiation environment within Orion on its unscrewed Artemis 1 flight. Zohar will on that flight wear an AstroRad Vest while Helga will not15. In 2016, human in the loop testing was conducted in the NASA JSC Orion medium-fidelity mockup to demonstrate how crew members might seek shelter during a radiation storm.
Future exploration vehicles being developed by NASA have smaller habitable volumes than the ISS, and as habitable volumes decrease, so must the toilet hardware. UWMS was designed to be more compact through the use of a dual-fan-rotary-separator and concentric odor-bacteria filter. The UWMS is currently scheduled to be installed on the ISS in the fall of 2019 and fly on the Orion EM-2 flight. Long gone are the days of the Apollo Waste Management system’s fecal bag17, think of a zip-lock with adhesive, although those will be aboard in case the toilet breaks down. For removing liquid waste, chemical tablets are mixed with the liquid waste to prevent precipitates from forming before it vents the urine overboard. The solid waste is not disposed of but is torrified18, that is it is heated-up to around 300°F to sterilize and remove any water, and then is compacted and stored. Biomass trash on Orion goes through a similar treatment in the Heat Melt Compactor (HMC), a device for reducing trash volume and stabilizing trash for long-term storage.
Like Apollo, Orion’s Launch Abort System (LAS) is a puller-style system using a solid-fueled tractor rocket that produces 8.8 million pounds of thrust19. It is designed to activate within milliseconds and offers the highest thrust and acceleration escape system ever tested. The Orion LASA is powerful enough to pull the Orion crew module beyond the debris field of the SLS rocket during an abort. And like Apollo, Orion successfully completed its Pad Abort Test (PA-1) on May 6, 2010 and its Ascent Abort (AA-2) test on July 2, 2019, both with flying colors.
Beyond weight, radiation, and waste management, there were other challenges that the Orion program faced, such as integrating the designs and requirements of the Orion crew and service vehicle, and the people building them. That meant getting NASA and the European Space Agency (ESA) to speak the same human spaceflight program language. ESA has never designed and built a crewed spacecraft while NASA has developed six (Mercury, Gemini, Apollo, Shuttle, and Orion). That means the perspective each agency comes from is different causing each to think differently about a great many things, from redundancy to testing, and so on. Over the years of working together, NASA and the ESA have learned how to bridge those differences in order to work together to design a safe and capable Orion service module, according to Korth.
All four RS-25 Shuttle veterans installed into SLS Core Stage
In a major milestone for NASA’s Space Launch System (SLS), all four RS-25 engines – veterans of the Space Shuttle Program (SSP) – have been installed into the core stage of the rocket that will conduct the maiden flight of NASA’s new monster rocket on the Artemis-1 mission.
SLS will use the full inventory of flight-proven Space Shuttle Main Engine (SSMEs), or RS-25Ds, before exhausting the stock and moving to the RS-25E.
The RS-25E – already contracted by NASA to Aerojet Rocketdyne – will be cheaper to build as the new engines will be specifically built as expendable units, as opposed to the built-in reusability of the RS-25D.
While many space fans are unhappy about the famous RS-25Ds being prepared for what will ultimately be a watery grave, SLS will benefit from the flight-proven experience of the engines for the opening missions.
All nine of the last SSMEs (Space Shuttle Main Engines) to fly with the Space Shuttle performed admirably, with Discovery flying Main Engine 1 (ME-1) – serial number 2044, ME-2 – 2048 and ME-3 – 2058 during her final mission, STS-133.
For Endeavour’s swansong, ME-1 – 2059, ME-2 – 2061, and ME-3 – 2057 helped begin the flight phase of the successful STS-134 mission, while Atlantis closed out the Space Shuttle Program, flying with engines ME-1 – 2047, ME-2 – 2060 and ME-3 – 2045 during STS-135.
Now prepared in sets of four, as opposed to flight sets of three during Shuttle, RS-25 installation tasks had to wait until the engine section was mated to the core section during processing at the Michoud Assembly Facility (MAF).
Once that milestone was achieved, engine installation began in mid-October with Engine 2056.
As a Block II engine, E2056 last rode two missions with Shuttle Discovery, famously with STS-114 as the program returned the United States to human spaceflight after the loss of Columbia.
It also remained with Discovery during the vehicle’s turnaround and launched on the follow-up mission, STS-121, before being placed into storage as a flight spare.
The second engine to be installed was E2045, a hugely experienced engine that has ridden with the Shuttle as a Block II since STS-110 with Atlantis in 2002.
Having also flown on STS-113, it then joined E2056 for the STS-121 flight on Discovery, meaning the two engines will once again launch together on the Artemis-1 mission.
E2056 also launched on the final Shuttle mission, helping Atlantis close out the program with the STS-135 mission in 2011.
The third engine to be installed into the SLS core stage was E2058, one of the newer engines – built as a Block II and debuting with STS-116, which saw Discovery launch to the ISS in 2006.
Launches with STS-120, STS-124, STS-119 and STS-129 followed, before its final launch – helping to push Discovery to the ISS on her final mission during STS-133.
NASA tweeted a picture of the third engine being bolted into the core stage, although it was later revealed the fourth engine was already in the process of being attached at the time NASA published the photos.
That pointed to a decreasing gap between each engine installation as engineers worked through the processing flow, potentially refining an installation roadmap during this first-time operation.
That final engine to be installed was E2060.
This unit has the least experience out of the four Artemis-1 engines having only flown three times, starting with its first launch powering Endeavour into orbit during STS-127. It then joined Discovery during the STS-133 mission before also closing out the Shuttle Program with the STS-135 launch involving Atlantis.
As such, there is a large amount of synergy with the Artemis-1 RS-25s, with E2060 once again joining forces with stablemates E2058 (from STS-133) along with E2045 and E2056 (from STS-135).
Per L2 information, all of the Block II RS-25Ds can now be accounted for, along with a few additions.
For Artemis-2, the first crewed mission of Orion, two first time flyers will be involved, namely E2062 and E2063.
E2063 was acceptance tested in October 2017, as a part of hot-fire testing in support of initial SLS certification – a program conducted at the Stennis Space Center. Both E2062 and E2063 are assigned to the second SLS launch and will serve as spares for the first launch campaign.
They will be joined by flight-proven RS-25Ds E2047 – vastly experienced with STS-112, 115, 118, 123, 126, 128, 132 and 134 under its belt as a Block II, along with E2059 – involved with lofting five Shuttle missions safely to orbit on STS-117, 122, 125 (to Hubble), STS-130 and finally with Discovery on STS-133.
For Artemis-3, SLS will return to four flight-proven RS-25s as a set, with E2061 (STS-130 and STS-134), E2057 (six missions, also completing its Shuttle role with STS-134), E2048 and E2054 (STS-133).
In addition to the above assignments, the other engines waiting for one final swansong with SLS are E2050 – which last flew with STS-120 and will fly on the fourth SLS mission along with E2051 and E2052 – which both flew with STS-132, and E2044 which last flew with STS-133 and Discovery.
Other notable engines from the Shuttle era are E2043 – which was a flown Block IIA engine/RS25C but was never flown in a full Block II configuration. E2049, 2053 and 2055 were lost with Columbia during the STS-107 disaster.
With four engines now installed into the core stage for the Artemis-1 mission, major milestones still lay ahead.
Next up will be the First Integrated Functional Test (FIFT) to check out the integrated core stage before preparations are made for the trip to Stennis on the Pegasus Barge.
It is hoped that this shipping milestone will occur in December, allowing for preparations early in 2020 for the huge event of the four RS-25s all firing up together during the Green Run test.
Should all proceed without major issues, the Core Stage can finally look forward to a trip to the launch site at the Kennedy Space Center. It will be put through an integration processing flow, where it will be lifted and stacked on to the Mobile Launcher (ML-1) inside the Vehicle Assembly Building (VAB).
The ML will already be hosting the two five-segment Solid Rocket Boosters (SRBs) on its deck by the time the Core Stage is lowered into place, following a path seen during the Space Shuttle Program where the External Tank was lowered into place between the two boosters.
Once the Core Stage is in place, the Upper Stage and Orion will arrive to be mated on top of the Core. The integrated Stack will then rollout of the VAB to Pad 39B in preparation for the maiden launch of the Space Launch System.
The actual launch date for Artemis-1 continues to be officially publicized as occurring in late 2020, although it is all-but-certain to move into 2021.