NASA and Boeing had cause to celebrate this morning as the Starliner CST-100 Orbital Flight Test came to an end at 1258 UT (0558 MST) 22 Dec 2019, with an early but normal landing at White Sands, New Mexico. Though the mission failed to reach the International Space Station, Starliner’s landing is a qualified first for the United States: Until today, no US space mission had successfully landed on firm ground without wings – though this is routine for Russian Soyuz missions. It is also the first time a crew-rated orbital spacecraft has landed at White Sands since STS-3 in 1982.
After winding past Australia in its final 261.5 x 246.4 km orbit, the Service Module performed a deorbit burn, then jettisoned into the Pacific Ocean. The Crew Module continued its northeasterly descent over Baja California, then into New Mexico. Both drogue parachutes deployed on time, slowing Starliner to subsonic velocity. All three main parachutes came out at the appropriate moment, bringing the vessel to its glacial landing pace of 8.5 meters per second. Finally, underneath Starliner, six landing airbags inflated to cushion its landing in the frigid desert dawn.
Upon arrival, Boeing’s ground teams, staffed from all over the United States, ran through all the standard procedures for vessel and crew recovery, from hydrazine approach safety, to static electricity grounding, to hatch opening one hour and two minutes after landing. The effort including staging a medical truck, as would be used to check the astronauts after an actual crewed mission.
As the vessel’s hatch opened and the cameras peered over the shoulders of the recovery crew, alongside numerous other well-secured bundles of undelivered cargo, the flight’s crash test dummy, Rosie the Rocketeer, could be seen strapped tightly into the commander’s seat. Anyone else who would have been there would have been just fine.
The post-launch press conference emphasized the landing as the primary goal of the Orbital Flight Test, and framed the mission as a substantial success. While all parties emphasized the need to conduct a complete review of flight data, Jim Chilton of Boeing said that as of Sunday morning, “60 percent” of the mission checklist had been completed, and proposed that, with the assumption that when data recovery from the Starliner is complete, “80 to 90 percent” of mission objectives will be met.
Missing the ISS was the mission’s most substantial loss. Further incomplete goals included tests of all components of the VESTA docking sensors, as well as failure to deliver time-sensitive mission cargo, including Christmas presents. Boeing and NASA will each take back their part of the recovered cargo, some of which may be flown to the ISS on later missions. The presents aboard will be given to astronauts when they return to Earth.
Boeing also flagged two minor problems during entry: a response delay in one of three navigation computers, which is of lesser concern as the system is designed to work with two out of three results, and the third was merely delayed, rather than incorrect or offline. The second issue was an error reported for nitrogen ullage in the crew module thruster system, which ground crews will attempt to trace to either a faulty sensor or an actual failure to close a valve.
The vessel will now spend two weeks in transit to Cape Canaveral, where it will be refurbished for its next mission, to be commanded by astronaut Sunita Williams, who gave a name to this particular Starliner capsule: Calypso, after the RV Calypso, French oceanographer Jacques Cousteau’s surface flagship. The USCV-2 mission will honour and continue that legacy of exploration, once another Starliner capsule has proven the system safe in crewed flight.
Despite a beautiful performance from its Atlas V N22 booster and dual-engine Centaur second stage at 11:36:43 UT 20 Dec 2019, Boeing’s CST-100 Starliner suffered a flight control anomaly half an hour into its flight. The vessel misfired its thrusters, placing the spacecraft designed to carry astronauts to the International Space Station in a low orbit, without enough fuel to both reach the ISS and safely return the vessel to Earth.
The misfire was thought to be the result of a computer software failure involving an incorrect time value. While astronauts Mike Fincke and Nicole Mann were confident that they could have resolved the situation almost instantly had they been aboard, the naturally slower ground response to the glitch took up precious time at a critical phase of flight. The situation was exacerbated as the vessel was flying in the switchover zone between two of NASA’s TDRS geosynchronous communication satellites.
NASA and Boeing agree that the vessel can still perform a normal landing at White Sands Space Harbour, New Mexico. However, it will do so without delivering its cargo to the space station, and will serve to end the 2010s, a decade notable for America’s lack of human spaceflight, on an off note. As the vessel is now responding to ground commands, Boeing and NASA engineers will evaluate the number of flight objectives that can be achieved.
Landing at White Sands will control the remaining timeline for the mission, because the vessel’s orbital track limits the number of chances. Also of note is Starliner’s altitude; its orbit, which at 1400 UT was roughly 216 x 186 km, is rather low, but the increased atmospheric drag will still be manageable if the mission timeline is kept short.
Because the onboard RCS motors discharged about 25% of the vessel’s fuel, the craft has much less hydrazine fuel aboard now than expected. As such, flight controllers will not be in a hurry to test non-essential flight operations, especially flips and rolls that don’t get them safely to New Mexico. There had been active debate about whether the vessel should still attempt to reach the ISS, which was almost certainly ruled out by the post-launch press conference. The problems will require full review of the root cause of the problem, in particular, if the onboard flight computer can be relied upon to execute the vessel’s landing sequence.
Failure and unexpected adversity are critical to the engineering process. At the same time, it is informative to observe that the root cause of the problem, possibly as simple as an incorrect clock, highlights the need for redundancy, error detection, and correction, in all key sensor and software systems. Still, reaching orbit in a crew-rated vessel remains a rarefied achievement, and despite the setback a great deal will be learned from this mission. The Starliner Orbital Flight Test can be counted as a successful failure.
Update: At ~0300 UT 21 Dec, Celestrak indicated the Starliner orbit to be 221 x 185 km. The 1400 UT 20 Dec value has been corrected in this article.
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