CTS-100 STARLINER— USA, 2019/2024

This is a traditional conical capsule which looks a lot like an Orion, only smaller and with fewer windows — one big square one and two little round ones, one of which is on the door (and the usual tiny one in the docking hatch). It also comes from a ULA partner, but the two have less in common than you’d expect. As hinted by the “liner” name, this comes from Boeing (the part which in a former life was mostly McDonnell Douglas)... but they got it from a smaller aerospace company named Bigelow, who started from a project originally called “Orion Lite” (which got early assistance from Lockheed’s Orion team) and diverged from there. So yeah, they may not have much in common, but originally they were supposed to have. They reached a point where they decided to throw out the Orion heritage and start clean; that was the best way to achieve lite-ness.

(Bigelow is a name we might have heard a lot more from. They were planning and designing the first private, for-profit space station! They have tested a small scale version of it as a module on the ISS. It’s inflatable! And then they wanted to put one in orbit around the moon. Robert Bigelow also runs a hotel chain called Budget Suites of America, and his eventual goal is to own hotels in space. There’s a rumor that he may be a UFO believer. The plan was to lift their station on a Vulcan — ULA would apparently be some sort of partner in the venture. One claimed advantage of the soft inflatable material is that it should be much better at blocking both radiation and micrometeorites than sheet metal is, though the tests of this in the small test version on the space station failed to bear out any claimed benefits on the radiation level. Unfortunately Bigelow laid off its entire workforce during the Covid-19 pandemic. They claim they will rehire them someday, but many did not believe this, and there’s no sign of any activity resuming.)

Unlike the Orion or the Dragon, this has no ambitions to go any further from Earth than the ISS or similar space stations. It could ride on any appropriately sized launch vehicle, and seat up to five people (it was originally going to be seven) in an 11 cubic meter cabin... as far as NASA is concerned, IIS flights would be limited to four seats, but Boeing talked them into adding a fifth seat, which they can sell to an IIS tourist. The size and dry mass and interior volume are roughly similar to those of the Dragon, though the shape is shorter and wider. It’s a bit roomier overall, but the layout gives less subjective feeling of space, at least to my eye.

It has a service module which is also short and wide, with four semi-large rocket nozzles sticking out, solar cells on the back between the nozzles, and heat radiators around the sides. The four nozzles are angled slightly outward — I don’t know why. The service module actually has three different sizes of motors: tiny for reaction control, moderate for orbital maneuvering, and the bigger four for launch escape (which look a bit undersized for the job), all sharing the same fuel supply. The reason the launch escape is divided into four is that the service module is hollow, with a little trunk area for cargo under the solar cells. The midsized orbital motors have a lot more muscle than the Dragon’s tiny thrusters, allowing it to quickly make orbit-change maneuvers which in a Dragon take many minutes. All of these minor thrusters are mounted in four rectangular “doghouse” boxes that stick out from the sides of the service module... and they’ve been been the most trouble-prone parts of the spacecraft. Total mass with the service module fueled is about 13 tons, just a hair more than the Dragon. (I don’t know the dry mass without the service module but I’m guessing 7 tons or less.)

They hope the capsule can be reusable for up to 100 flights, whereas the Orion is only trying for ten at the most. For the near term, they planned to launch the Starliner with an Atlas V, then switch to Vulcan. They use airbags for landing on dirt. Unlike the Orion’s proposed bags, which would have had to wrap awkwardly around the sides, the Starliner’s approach is to jettison the heat shield while suspended by the parachutes, so the airbags can come right out the bottom. I guess replacing the heat shield each time is a pretty good way to make a capsule last for a hundred flights.

Once docked, they could use the maneuvering thrusters to boost the station’s orbit, because the service module and its fuel are going to be discarded anyway. This needs doing on a fairly regular basis, and other service modules, notably the one used on the ATV cargo canister and since given to the Orion, have performed this orbit-raising service in the past. In theory it should have been possible for the Dragon to also perform this service, but they can’t spare the fuel, as its total supply of fuel is smaller than that of the Starliner, and for some reason they use a lot of it to raise their orbit to space station altitudes. Boosting the ISS while docked to the American end would first require using its gyros to turn the whole station over so it’s facing backwards. The station also has its own orbit-raising motors in the Russian section, so the job could be done by simply delivering fuel for them instead of by actively pushing the station, but these are disused and possibly no longer functional, so nowadays they always use an attached craft. If nothing better is available they’ll use the tiny reaction-control thrusters on a Progress capsule, though this is inefficient and tedious. All it all, it needs about four tons a year of propellant to keep the station from falling down, which is about one percent of its total mass. It used to need seven, due to being in a lower orbit so the Shuttle could dock with it. If they ever replace the Soyuz maybe it could go higher, but the current plan is to retire the ISS, because it may be increasingly unsafe as parts wear out.

getting it operational

For years we were in suspense waiting to see which would carry passengers first, the Starliner or the Dragon 2. Originally the Dragon was scheduled much earlier, but SpaceX’s scheduled dates were, as always, more expressions of hope than of confidence. At the beginning of 2019, the two looked to be roughly neck and neck... then Dragon was the first to pull off an unmanned flight to the space station, and shortly after, rumors started to emerge of further delays for the Starliner, so it might not be ready for crewed flight before the end of the year. But then a static test of the SuperDraco motors on the used Dragon capsule caused an explosion that destroyed the entire craft. So at this point it looked like the odds favored the Starliner being the first to carry astronauts. But it had its own delays, and some of them were also due to difficulty with the launch escape system, which like that of the Dragon uses hypergolic fuel, because the people who run the Space Station don’t approve of docking solid rockets to it. They are not safe in an environment which is being alternately baked and frozen sixteen times a day. Apparently Boeing’s escape rockets have suffered from fuel leaks.

After resolving the escape rocket issues, their launch abort test had a chute that didn’t open, and an excessive release of hypergolic fuel, which is too toxic to tolerate leaks of. And then, once they finally launched it to orbit uncrewed, to catch up to where the Dragon got to the previous spring, it went off course and didn’t reach the space station, due to a software error in the service module that threw off its clock and caused it to waste fuel. Then they spotted another software issue in the nick of time, which without a quick patch, would have made it unsafe to detatch the service module for reentry.  Upon later scrutiny it also came out that a few of the reaction control thrusters had not worked right, again due to software, which apparently had an incorrect map of which thruster was which. NASA found that the whole QA process at Boeing was substandard — an issue that also played a part in the 737 Max scandal, as the entire company had undergone a shift toward trying to cut too many corners. (It’s said that the reckless profit-first culture which is now ruining Boeing came from the McDonnell-Douglas side; their people ended up in charge of the civilian airliners even though at the time of the merger, Douglas planes were market failures compared to Boeing’s obviously superior aircraft.) For a while the possibility stayed open that once debugging was completed, the next flight attempt would be crewed, but eventually Boeing decided to redo the test launch at their own expense, which pushed the crewed flight out to 2021... which became 2022 and then 2023. By the time this plan was settled, the Dragon had flown two test pilots to the station and back without incident. Before that second test flight went up, Dragon launched two full crews of four, and before the ’Liner finally took a live crew onboard, Dragon had carried fifty people on thirteen flights. (But it did beat the Orion’s first crewed flight.)

Why the further delay? When the second test launch rolled out to the pad, they had to scrub because sensors reported an incorrectly set valve. They tried to quickly resolve this, but it turned out to be not one balky valve, but thirteen of them. They had to drain the fuel, roll the whole rocket back to the assembly building, and unstack it. They then spent days coaxing one valve after another back into operation, using “mechanical, electrical, and thermal techniques”, which doesn’t sound reassuring for how reliable the unjammed valves would be in the future. Finally they had to ship the whole spacecraft back to the factory. They fussed over the service module for weeks and in the end junked it entirely, mating a new one to the capsule in order to retry the flight. This finally went up in the spring of 2022... and had two more maneuvering thrusters quit working during orbital insertion, and apparently two little reaction jets also took some time off (though they became usable again later) before it finally approached the ISS... at which time they had trouble with a balky docking ring. There was also some issue with the cooling system for the cabin. At least the landing went smoothly, though an unconfirmed story says another reaction jet failed during reentry, this time one on the capsule itself rather than on the service module.

From the bad escape-motor test to the glitch on the nominally successful docking flight, one thing that has repeatedly given them trouble has been the valves that send hypergolic propellant to the motors. When they tore open the bad service module, they found corrosion in them. A trace of leakage, combined with Florida humidity, ended up producing nitric acid, among other nasty byproducts. Boeing pointed the finger at the valve builder, Aerojet-Rocketdyne, who pointed back at Boeing’s design. Apparently neither had thought to test the valves in humid conditions, and both were generally communicating with each other as little as they could due to having long since pissed each other off in squabbles over money. This specific issue did not recur in flight, but it’s clearly not the only way the hypergolic propellant flow is failing to start and stop reliably.

Trouble with hypergolic leakage is historically not rare, and around this time a cargo Dragon also had an issue where some toxic smells escaped and set off alarms. But the frequency and severity of issues on the Starliner service module definitely stands out.

In mid-2023, some weeks before they were about to finally launch astronauts, someone discovered that the fiberglass tape which was wrapped around all the wiring harnesses was a fire hazard... and also that some of the parachute attachment bits were weaker than they were meant to be. A chute fix was simple enough, but redoing all the wiring harnesses was quite a headache. That pushed back the next attempt well into the next spring. Once they got the wiring done (which in some cases involved just putting good tape on top of the bad stuff), additional delays not caused by Starliner pushed the launch back a couple more months.

the “stranded astronaut” debacle

Finally, in June of 2024, veteran astronauts Butch Wilmore and Suni Williams (the first woman to test-pilot a new spacecraft) rode the Calypso up to the ISS, with me worrying the whole way for their safety. (I will give them this: Calypso — taken from Jacques Cousteau’s ship — is a cooler name than any of the Dragons have. Credit for picking that name goes to Suni. This is the same Starliner that was used in the first uncrewed test flight in 2019 — the one that failed to even reach the ISS orbit — and at this rate may end up being the only one with a name.) They were supposed to spend only eight days at the station.

Problems continued to crop up: first a slow helium leak, then four more, and then, more seriously, several balky thrusters. All of these were issues of the service module, not the capsule. The thruster problem made them postpone docking for an hour while they exercised them and got some of them unstuck, and eventually they were okay to dock. Worries over the leaks and thrusters ended up repeatedly delaying their return from orbit. This was a highly publicized embarrassment for both Boeing and NASA, accompanied by memes such as Princess Leia saying “You came in that thing? You’re braver than I thought.”

And while they were up there, a routine Falcon 9 launch experienced a blown engine when relighting the upper stage, meaning that they also needed to delay crew flights on Dragon capsules for a while, leaving the USA with no usable spacecraft. But this was brief, as the Falcon was cleared to fly people again with uncharacteristic — one might even say suspicious — haste. Then it was paused again when an upper stage was off-target on its reentry burn.

During this extended orbital stay, engineers found the main reason why the valves got stuck: they were overheating. The “doghouse” side pods are overly insulated, and for the thrusters to keep cool enough you must avoid using them heavily. In the worst cases, soft teflon gaskets could lose their shape and cause blockages... and a reentry burn could soak it with enough heat for this to happen. So they couldn’t be sure it was safe to ride home in. They left it on the station as long as they could, with Butch and Suni getting months of bonus ISS time, while trying to get a definite answer about safety. They even exercised the thrusters while attached to the station. And while cautiously resuming uncrewed Falcon flights, a Cygnus cargo capsule failed twice to perform its orbit-raising burn, completing a trifecta of glitches on America’s ISS-servicing vehicles. Fortunately the third try at starting the Cygnus succeeded, so the unintentionally oversized ISS crew got their groceries.

Finally, after trying for most of the summer to see if they could model and predict the thermal problem well enough to find a workaround which would let them get the thing back safely with people on board, NASA ran out of time and called it: Calypso would return empty. Though reluctant, the decision was essentially unanimous, and widely hailed as correct and necessary. This means that Butch and Suni got volunteered to stay up there for an oversized eight month tour (for the latter five of which Suni would be appointed as station commander), and two of the astronauts who had been going to ride up on Crew 9 (both being women) would have to stay home. The Freedom would go up with only two people, but four space suits, as the SpaceX and Boeing suits are not compatible, and they’d have to make a new pair of Dragon suits to Butch and Suni’s measurements for their return flight. NASA’s whole schedule is thrown way off, with indirect consequences spreading annoyance and inconvenience for all.

And for dessert, the ’Liner had one more glitch to offer before leaving: weird bonging noises coming out of the internal speakers because the communications system had got into some sort of feedback loop. Not long after that one was figured out, the thing backed away from the ISS (and did so in an unusually hurried fashion to minimize exposure of the station to any new malfunction it might develop), then reentered and landed without further incident. Except, that is, for a brief outage in the navigation software. And that one plugged thruster was still offline for the departure. But at this point, who’s counting?

All in all, the Starliner has been looking like a clusterfuck. Sure, 99% of it is fine, but in aerospace being 99% right gets people killed. If they haven’t fully corrected the propellant valves, that service module will continue to be a danger not just to anyone who rides it, but to any station it docks to. SpaceX once had a valve problem on their escape motors similar to the earlier issue that Starliner had with seepage and corrosion, and it blew up the whole capsule during a test firing. They fixed it with burst discs, which positively stop all leakage, but that fix isn’t applicable to maneuvering thrusters, only to escape rockets that normally go unused. Now that live people are riding it, I sure hope these glitches can be put behind us, but it’s going to be some time before we can start feeling confident about that. Since the doghouse thermal issue doesn’t affect the spacecraft itself as far as we know, the Calypso may set sail again, if a doghouse 2.0 can be made for the next service module, but getting that certified for flight is going to take some time, and it’ll still be hard to trust that it’s safe to fly.

In the end, NASA bought additional flights from SpaceX to carry most of the astronauts that were supposed to go up on Starliners. They aren’t giving up on Boeing entirely — they still want to get six crewed flights out of them, though there is hardly time remaining for that in the schedule before the ISS is decommissioned — but they clearly have decided not to count on them either. They may also be reopening opportunities for other spacecraft projects such as Dream Chaser to bid on making crewed flights.

There are two Starliner craft nominally in service: number S2 (which performed the second uncrewed flight test), and S3 (the Calypso). Boeing still plans on S2 getting a crew and a name. They originally thought they would make a fleet of three, but of course there is little chance that any customers for another one are going to be forthcoming.