In and around Cape Canaveral is all about Artemis. Colorful, hand -painted posters with the inscription "Go Artemis!" The shop windows of the shops decorate. Large provisional street signs indicate the starting day. Astronauts, NASA officials and managers from the aerospace industry are crowded in the bars, in which there is a lot of talk about the show program of NASA to research space by humans.
"We're launching," NASA announced in the days leading up to the scheduled launch of its Artemis I mission. As part of the mission, a launch vehicle called "Space Launch System" (SLS) and a spacecraft for crew named "Orion" will be tested for the first time. Artemis, named after the sister of the Greek god Apollo, is NASA's lunar project. She wants to take people back to the moon, maybe even to Mars.
But first, the SLS must first take off from Earth. NASA's first two launch attempts, which had been scheduled for August 29 and September 3, 2022 at the agency's Kennedy Space Center (KSC), failed. The next test is tentatively scheduled for September 27, with a possible replacement date on October 2, provided that a fuel test is successful and the launch permit is granted.
"What we see on the starting ramp is actually typical of new carrier systems when they are put into operation for the first time," says Daniel Dumbacher, who supervised the initial development of the SLS when he was at NASA, and now as managing director of the American Institute of Aeronautics and Astronautics. “That doesn't get me a bit. It is a delay, yes, but on the whole we restore the starting capacity that this country has given up to Apollo. «
While NASA employees are continuing to troubleshoot the rocket, the rhetoric has changed somewhat: they keep stressing that Artemis I is a test flight, and a risky one at that. After all, the rocket is new – even if its design is based on the technology from the space shuttle from the past. And the spacecraft at the top is also new. If all goes well, the SLS will send the unmanned Orion space capsule on a trip around the Moon. Then afterwards the capsule will have to prove that it also withstands the high-speed re-entry into the Earth's atmosphere.
There is a lot at stake. The SLS and the Orion room capsule lie above the budget and come to the starting point too late for years, which has already devoured $ 43 billion in tax money. And for others, the problems with which NASA has to struggle with the start of Artemis are not unexpected for another reason.
"I'm not too surprised," says Lori Garver, former NASA deputy administrator and avowed critic of Artemis hardware. This is partly due to the fact that the decisions made more than a decade ago would chain those responsible to a design that was not really geared towards operability.
SLS and Orion are equipped with parts built by several long-established aerospace companies – not because NASA had these requirements for their mission, but because influential congressmen such as then Senator Bill Nelson (now NASA administrator) exerted political pressure to keep money flowing to their district or state. The result is an unwieldy structure that is based on outdated technology and is jokingly also referred to as the "Senate Launch System". Together with Orion, it devours about $ 4 billion per launch. When the SLS takes off from the launch pad, apart from the Orion space capsule and secondary payloads, the rest of the expensive system will end up in the sea or as space junk.
This has been contrary to companies such as SpaceX, which relies on largely reusable rockets and has started five missiles from Cape Canaveral since NASA rolled the SLS on August 16, 2022 gen starting ramp. The largest, currently in operation, reusable rocket from SpaceX, the Falcon Heavy, has already flown to space three times. Depending on the specific mission profile and the final destination in the orbit, the Falcon Heavy can transport about two thirds of the payload of the SLS under the cheapest circumstances, with each start costs about $ 100 million.
First attempt at launch
The evening before the first attempt to start, which was scheduled for August 29 at 8.33 a.m., tens of thousands of onlookers and hundreds of space journalists were already frolicking at the »Space Coast«, which includes the KSC and the surrounding region in Florida. All eyes were aimed at the SLS and the Orion room capsule, which were stacked like a white-icing-colored statue in the floodlights of the KSC start complex 39 like an almost 100 meter high. The process of refueling the rocket should begin shortly. The hopes for the start the next day were great, but the first problems occurred during the night.
Initially, there were weather-related delays. By midnight, the probability of a lightning strike near the launch pad was too high for the team to begin refueling the rocket. After about an hour, the thunderstorms cleared, and you could finally get started. Refueling the SLS means pumping about 190,000 gallons of cryogenic liquid oxygen and 538,000 gallons of supercooled liquid hydrogen into the main stage tank. This is a delicate undertaking, because cryogenic fuels are notoriously slippery – and explosive.
Soon the team discovered a hydrogen leak at the base of the rocket. The same problem had already occurred during a "dress rehearsal" and had often delayed the launch of space shuttles in the past: in the past 30 years, the launches of NASA's space shuttles had to be stalled on average once per launch – often due to hydrogen leaks.
As the smallest and lightest atom in the universe, hydrogen is an excellent fuel, but he is also a master of volatility. "It is an insidious little molecule that always finds ways to escape," says Dumbacher. "The problem is that it can burn in sufficient concentration of places where it shouldn't burn."
The team continued and sealed the leak. The refuel was continued. Then there was a crack in the foam that isolated the main level of the SLS, but the team members decided that this was not a problem and continued. But soon afterwards there was a problem that they could not simply overlook: According to sensors, one of the four engines of the rocket was not cooled down to the correct temperature, during a process that is referred to as the "chilldown" and the engines to prepare for the cold shock through the hypothermic liquid hydrogen. Usually the teams let a small amount of minus 252 degrees Celsius cold fuel run through the system to condition the four engines before the start, but the number three of the engine did not seem to react to it. Launch Director Charlie Blackwell-Thompson therefore explained the demolition around 8.40 a.m., and the huge countdown clock stopped at minus 40 minutes.
A few days later, NASA officials announced that the cooling procedure had probably gone flawlessly. The team had enough data to indicate that the coolant had flowed properly, and the engineers decided that the sensor that had indicated an abnormally high temperature was probably just defective. They would make a second attempt without repairing. "Is it part of the plan... just ignore the sensor?" asked CNN correspondent Kristin Fisher during a briefing on September 1. Yes," replied SLS chief engineer John Blevins, "we will."
"It is not uncommon that there are problems with the instruments. The public is just not used to it," says Dumbacher.
Attempt number two
The next launch attempt was scheduled for September 3, with a two-hour launch window opening at 2:17 p.m. ET. With Labor Day approaching in the US, the holiday weekend attracted even more people – this time around 400,000 gathered.
But even on this date, the problems quickly piled up. The refueling started on time, but the employees discovered – damn it again! - almost immediately another hydrogen leak. They tried to fix it by heating the filling lines and pressurizing them with helium, but the leak was too big. After three attempts, it was beyond repair – by 11 o'clock the team was already far behind its schedule. Since the hydrogen tank was only eleven percent full, Blackwell-Thompson aborted the launch again.
Artemis mission manager Mike Sarafin later explained during a briefing that the hydrogen leak had occurred at the same place at which a manually entered command led to an "accidental overpressure in the hydrogen transfer line" and increased the pressure on two or three times. The overpressure may have damaged the poetry at this connecting site. "There was a sequence of about a dozen commands that were necessary and the wrong valve was simply controlled," said Sarafin. "This was a manual sequence, and the fact that we did not automate this special sequence could have been a reason for the unintentional overpressure."
As of September 20, 2022, NASA employees have not yet been able to definitively link the error to the hydrogen leak that caused the launch abort again. They are still conducting a "fault tree analysis", which will ultimately reveal the cause of the leak.
But even if the incorrect command did not cause the leak, this is not good news, says Garver. »At this point, you no longer send erroneous commands that expose a line over pressure. They say that the process might have been automated. But with a 43 billion dollar project, you don't face 'Oh, yes, maybe we should have done it' questions more. «
Are there three good things in all?
According to NASA, several seals have now been repaired on the starting ramp. A third attempt to start was nevertheless postponed from September 23 to September 27th. And also whether September 27 can be observed is still unclear. NASA recently successfully completed a trial tank, but again a leak appeared, as the German press agency reported. However, the leak has probably moved in a tolerable frame.
For a start at the end of September, however, not only the technical conditions have to be right. Among other things, Space Launch Delta 45, a unit of the Space Force that grants permission for all rocket launches on the Eastern Range, must submit a waiver. Because the SLS was only approved for the start until 6 September. The batteries for the onboard self-destruct system – basically a bomb designed to destroy the missile if it deviates from course and threatens an inhabited area – must be recharged, which is only possible at KSC's nearby Vehicle Assembly Building (VAB).
A launch at the end of September would require Space Launch Delta 45, which is responsible for public safety, to refrain from recharging. If this is not possible, NASA will have to return to the VAB and try to find a launch window for mid–October - a consequence of opting for a minimalist launch pad that does not have the required loading capacity.
"I don't think you are aware of how some of the early decisions made under the pressure of the budget have an impact today," says Dumbacher. He refers primarily to the reduced start and the selection of Kryo fuels.
However, he also says: "I keep hearing talk about not using new technology. But I also want to remind people that the laws of physics have not changed." The liquid oxygen and liquid hydrogen system is "what Mother Nature has provided us to achieve our mission goals. It has the necessary energy to launch large systems, large masses and large volumes into orbit and on the way to the Moon and, finally, to Mars.«
NASA's recent problems in the area of manned space travel come at a suitable time: On September 12, there was talk for the 60th time, in which President John F. Kennedy once announced: »We decided to go to the moon in this decade To fly and do the other things, not because they are simple, but because they are difficult. ”60 years later, the most famous space agency in the world may be more difficult to overcome the political forces they keep on the ground Gravity.
© Springer Nature LimitedScientific American, «NASA's Artemis Delays Fuel Controversy over Rocket Design», 2022
