Enlarge/ A European ATV cargo freighter reenters the atmosphere over the Pacific Ocean in 2013.
Since the beginning of the year, landowners have discovered several pieces of space junk traced to missions supporting the International Space Station. On all of these occasions, engineers expected none of the disposable hardware would survive the scorching heat of reentry and make it to Earth’s surface.
These incidents highlight an urgency for more research into what happens when a spacecraft makes an uncontrolled reentry into the atmosphere, according to engineers from the Aerospace Corporation, a federally funded research center based in El Segundo, California. More stuff is getting launched into space than ever before, and the trend will continue as companies deploy more satellite constellations and field heavier rockets.
“The biggest immediate need now is just to do some more work to really understand this whole process and to be in a position to be ready to accommodate new materials, new operational approaches as they happen more quickly,” said Marlon Sorge, executive director of Aerospace’s Center for Orbital and Reentry Debris Studies. “Clearly, that’s the direction that spaceflight is going.”
Ideally, a satellite or rocket body at the end of its life could be guided to a controlled reentry into the atmosphere over a remote part of the ocean. But this is often cost-prohibitive because it would require carrying extra fuel for the de-orbit maneuvers, and in many cases, a spacecraft doesn’t have any rocket thrusters at all.
In March, a fragment from a battery pack jettisoned from the space station punched a hole in the roof of a Florida home, a rare instance of terrestrial property damage attributed to a piece of space junk. In May, a 90-pound chunk of a SpaceX Dragon spacecraft that departed the International Space Station fell on the property of a “glamping” resort in North Carolina. At the same time, a homeowner in a nearby town found a smaller piece of material that also appeared to be from the same Dragon mission.
These events followed the discovery in April of another nearly 90-pound piece of debris from a Dragon capsule on a farm in the Canadian province of Saskatchewan. NASA and SpaceX later determined the debris fell from orbit in February, and earlier this month, SpaceX employees came to the farm to retrieve the wreckage, according to CBC.
Pieces of a Dragon spacecraft also fell over Colorado last year, and a farmer in Australia found debris from a Dragon capsule on his land in 2022.
Enlarge/ Boeing’s Starliner spacecraft is seen docked at the International Space Station on June 13.
NASA and Boeing officials pushed back Friday on headlines that the commercial Starliner crew capsule is stranded at the International Space Station but said they need more time to analyze data before formally clearing the spacecraft for undocking and reentry.
Two NASA astronauts, commander Butch Wilmore and pilot Suni Williams, will spend at least a few more weeks on the space station as engineers on the ground conduct thruster tests to better understand issues with the Starliner propulsion system in orbit. Wilmore and Williams launched June 5 aboard an Atlas V rocket and docked at the station the next day, completing the first segment of Starliner’s first test flight with astronauts.
NASA managers originally planned for the Starliner spacecraft to remain docked at the space station for at least eight days, although they left open the possibility of a mission extension. The test flight is now likely to last at least a month and a half, and perhaps longer, as engineers wrestle with helium leaks and thruster glitches on Starliner’s service module.
Batteries on this Starliner spacecraft were initially only certified for a 45-day mission duration, but NASA officials said they are looking at extending the limit after confirming the batteries are functioning well.
“We have the luxury of time,” said Ken Bowersox, associate administrator for NASA’s space operations mission directorate. “We’re still in the middle of a test mission. We’re still pressing forward.”
Previously, NASA and Boeing officials delayed Starliner’s reentry and landing from mid-June, then from June 26, and now they have bypassed a potential landing opportunity in early July. Last week, NASA said in a statement that the agency’s top leadership will meet to formally review the readiness of Starliner for reentry, something that wasn’t part of the original plan.
“We’re not stuck on ISS”
Steve Stich, manager of NASA’s commercial crew program, said Friday that he wanted to clear up “misunderstandings” that led to headlines claiming the Starliner spacecraft was stuck or stranded at the space station.
“I want to make it very clear that Butch and Suni are not stranded in space,” Stich said. “Our plan is to continue to return them on Starliner and return them home at the right time. We have a little bit more work to do to get there for the final return, but they’re safe on (the) space station.”
With Starliner docked, the space station currently hosts three different crew spacecraft, including SpaceX’s Crew Dragon and Russia’s Soyuz. There are no serious plans under consideration to bring Wilmore and Williams home on a different spacecraft.
“Obviously, we have the luxury of having multiple vehicles, and we work contingency plans for lots of different cases, but right now, we’re really focused on returning Butch and Suni on Starliner,” Stich said.
“We’re not stuck on the ISS,” said Mark Nappi, Boeing’s vice president in charge of the Starliner program. “It’s pretty painful to read the things that are out there. We’ve gotten a really good test flight that’s been accomplished so far, and it’s being viewed rather negatively.”
Stich said NASA officials should have “more frequent interaction” with reporters to fill in gaps of information on the Starliner test flight. NASA’s written updates are not always timely, and often lack details and context.
NASA officials have cleared the Starliner spacecraft for an emergency return to Earth if astronauts need to evacuate the space station for safety or medical reasons. But NASA hasn’t yet approved Starliner for reentry and landing under “nominal” conditions.
“When it is a contingency situation, we’re ready to put the crew on the spacecraft and bring them home as a lifeboat,” Bowersox said. “For the nominal entry, we want to look at the data more before we make the final call to put the crew aboard the vehicle, and it’s a serious enough call that we’ll bring the senior management team together (for approval).”
Enlarge/ Illustration of the SpaceX Dragon XL as it is deployed from the Falcon Heavy’s second stage in high Earth orbit on its way to the Gateway in lunar orbit.
SpaceX
NASA has awarded an $843 million contract to SpaceX to develop a “US Deorbit Vehicle.” This spacecraft will dock to the International Space Station in 2029 and then ensure the large facility makes a controlled reentry through Earth’s atmosphere before splashing into the ocean in 2030.
“Selecting a US Deorbit Vehicle for the International Space Station will help NASA and its international partners ensure a safe and responsible transition in low Earth orbit at the end of station operations,” said Ken Bowersox, NASA’s associate administrator for Space Operations, in a statement. “This decision also supports NASA’s plans for future commercial destinations and allows for the continued use of space near Earth.”
NASA has a couple of reasons for bringing the space station’s life to a close in 2030. Foremost among these is that the station is aging. Parts of it are now a quarter of a century old. There are cracks on the Russian segment of the space station that are spreading. Although the station could likely be maintained beyond 2030, it would require increasing amounts of crew time to keep flying the station safely.
Additionally, NASA is seeking to foster a commercial economy in low-Earth orbit. To that end, it is working with several private companies to develop commercial space stations that would be able to house NASA astronauts, as well as those from other countries and private citizens, by or before 2030. By setting an end date for the station’s lifetime and sticking with it, NASA can help those private companies raise money from investors.
Do we have to sink the station?
The station, the largest object humans have ever constructed in space, is too large to allow it to make an uncontrolled return to Earth. It has a mass of 450 metric tons and is about the size of an American football field. The threat to human life and property is too great. Hence the need for a deorbit vehicle.
The space agency considered alternatives to splashing the station down into a remote area of an ocean. One option involved moving the station into a stable parking orbit at 40,000 km above Earth, above geostationary orbit. However, the agency said this would require 3,900 m/s of delta-V, compared to the approximately 47 m/s of delta-V needed to deorbit the station. In terms of propellant, NASA estimated moving to a higher orbit would require 900 metric tons, or the equivalent of 150 to 250 cargo supply vehicles.
NASA also considered partially disassembling the station before its reentry but found this would be much more complex and risky than a controlled deorbit that kept the complex intact.
The NASA announcement did not specify what vehicle SpaceX would use to perform the deorbit burn, but we can draw some clues from the public documents for the contract procurement. For example, NASA will select a rocket for the mission at a later date, but probably no later than 2026. This would support a launch date in 2029, to have the deorbit vehicle docked to the station one year before the planned reentry.
Enlarge/ Illustration of the Apollo lunar lander Eagle over the Moon.
On Friday, a retired software engineer named Martin C. Martin announced that he recently discovered a bug in the original Lunar Lander computer game’s physics code while tinkering with the software. Created by a 17-year-old high school student named Jim Storer in 1969, this primordial game rendered the action only as text status updates on a teletype, but it set the stage for future versions to come.
The legendary game—which Storer developed on a PDP-8 minicomputer in a programming language called FOCAL just months after Neil Armstrong and Buzz Aldrin made their historic moonwalks—allows players to control a lunar module’s descent onto the Moon’s surface. Players must carefully manage their fuel usage to achieve a gentle landing, making critical decisions every ten seconds to burn the right amount of fuel.
In 2009, just short of the 40th anniversary of the first Moon landing, I set out to find the author of the original Lunar Lander game, which was then primarily known as a graphical game, thanks to the graphical version from 1974 and a 1979 Atari arcade title. When I discovered that Storer created the oldest known version as a teletype game, I interviewed him and wrote up a history of the game. Storer later released the source code to the original game, written in FOCAL, on his website.
Enlarge/ A scan of printed teletype output from the original Lunar Lander game, provided by Jim Storer.
Jim Storer
Fast forward to 2024, when Martin—an AI expert, game developer, and former postdoctoral associate at MIT—stumbled upon a bug in Storer’s high school code while exploring what he believed was the optimal strategy for landing the module with maximum fuel efficiency—a technique known among Kerbal Space Program enthusiasts as the “suicide burn.” This method involves falling freely to build up speed and then igniting the engines at the last possible moment to slow down just enough to touch down safely. He also tried another approach—a more gentle landing.
“I recently explored the optimal fuel burn schedule to land as gently as possible and with maximum remaining fuel,” Martin wrote on his blog. “Surprisingly, the theoretical best strategy didn’t work. The game falsely thinks the lander doesn’t touch down on the surface when in fact it does. Digging in, I was amazed by the sophisticated physics and numerical computing in the game. Eventually I found a bug: a missing ‘divide by two’ that had seemingly gone unnoticed for nearly 55 years.”
A matter of division
Enlarge/ Diagram of launch escape system on top of the Apollo capsule.
NASA
Despite applying what should have been a textbook landing strategy, Martin found that the game inconsistently reported that the lander had missed the Moon’s surface entirely. Intrigued by the anomaly, Martin dug into the game’s source code and discovered that the landing algorithm was based on highly sophisticated physics for its time, including the Tsiolkovsky rocket equation and a Taylor series expansion.
As mentioned in the quote above, the root of the problem was a simple computational oversight—a missing division by two in the formula used to calculate the lander’s trajectory. This seemingly minor error had big consequences, causing the simulation to underestimate the time until the lander reached its lowest trajectory point and miscalculate the landing.
Despite the bug, Martin was impressed that Storer, then a high school senior, managed to incorporate advanced mathematical concepts into his game, a feat that remains impressive even by today’s standards. Martin reached out to Storer himself, and the Lunar Lander author told Martin that his father was a physicist who helped him derive the equations used in the game simulation.
While people played and enjoyed Storer’s game for years with the bug in place, it goes to show that realism isn’t always the most important part of a compelling interactive experience. And thankfully for Aldrin and Armstrong, the real Apollo lunar landing experience didn’t suffer from the same issue.
You can read more about Martin’s exciting debugging adventure over on his blog.
Enlarge/ Astronauts Suni Williams and Butch Wilmore, wearing their Boeing spacesuits, leave NASA’s crew quarters during a launch attempt May 6.
Fresh off repairs at the launch pad in Florida, United Launch Alliance engineers restarted the countdown overnight for the third attempt to send an Atlas V rocket and Boeing’s Starliner spacecraft on a test flight to the International Space Station.
NASA astronauts Butch Wilmore and Suni Williams were expected to awake early Wednesday, put on their blue pressure suits, and head to the launch pad at Cape Canaveral Space Force Station to board the Starliner capsule on top of the 172-foot-tall Atlas V rocket.
Once more through the door
Wilmore and Williams have done this twice before in hopes of launching into space on the first crew flight of Boeing’s Starliner spacecraft. A faulty valve on the Atlas V rocket prevented liftoff May 6, then engineers discovered a helium leak on the Starliner capsule itself. After several weeks of troubleshooting, NASA and Boeing officials decided to proceed with another launch attempt Saturday.
Everything seemed to be coming together for Boeing’s long-delayed crew test flight until a computer problem triggered an automatic hold in the countdown less than four minutes before liftoff. Technicians from United Launch Alliance (ULA), the Atlas V rocket’s builder and operator, traced the problem to a failed power distribution source connected to a ground computer responsible for controlling the final phase of the countdown.
The instantaneous launch opportunity Wednesday is set for 10: 52 am EDT (14: 52 UTC), when the launch site at Cape Canaveral passes underneath the space station’s orbital plane. Forecasters predict a 90 percent chance of good weather for launch. You can watch NASA’s live coverage in the video embedded below.
The countdown began late Tuesday night with the power-up of the Atlas V rocket, which was set to be filled with cryogenic liquid hydrogen and liquid oxygen propellants around 5 am EDT (09: 00 UTC). Kerosene fuel was loaded into the Atlas V’s first-stage booster prior to the mission’s first launch attempt in early May.
The two Starliner astronauts departed crew quarters at NASA’s Kennedy Space Center for the 20-minute drive to the launch pad, where they arrived shortly before 8 am EDT (12: 00 UTC) to climb into their seats inside the Starliner capsule. After pressure checks of the astronauts’ suits and Starliner’s crew cabin, ground teams will evacuate the pad about an hour before launch.
Assuming all systems are “go” for launch, the Atlas V will ignite its Russian-made RD-180 main engine and two solid-fueled boosters to vault away from Cape Canaveral and head northeast over the Atlantic Ocean. Wilmore and Williams will be not only the first people to fly in space on Boeing’s Starliner, but also the first astronauts to ride on an Atlas V rocket, which has flown 99 times before with satellites for the US military, NASA, and commercial customers.
The rocket’s Centaur upper stage will deploy Starliner into space around 15 minutes after liftoff. A critical burn by Starliner’s engines will happen around 31 minutes into the flight to finish the task of placing it into low-Earth orbit, setting it up for an automated docking at the International Space Station at 12: 15 pm EDT (16: 15 UTC) Thursday.
The two-person crew will stay on the station for at least a week, although a mission extension is likely if the mission is going well. Officials may decide to extend the mission to complete more tests or to wait for optimal weather conditions at Starliner’s primary and backup landing sites in New Mexico and Arizona. When weather conditions look favorable, Starliner will undock from the space station and head for landing under parachutes.
The crew test flight is a prerequisite to Boeing’s crew capsule becoming operational for NASA, which awarded multibillion-dollar commercial crew contracts to Boeing and SpaceX in 2014. SpaceX’s Crew Dragon started flying astronauts in 2020, while Boeing’s project has been stricken by years of delays.
Wilmore and Williams, both former US Navy test pilots, will take over manual control of Starliner at several points during the test flight. They will evaluate the spacecraft’s flying characteristics and accommodations for future flights, which will carry four astronauts at a time rather than two.
“The expectation from the media should not be perfection,” Wilmore told Ars earlier this year. “This is a test flight. Flying and operating in space is hard. It’s really hard, and we’re going to find some stuff. That’s expected. It’s the first flight where we are integrating the full capabilities of this spacecraft.”
Enlarge/ NASA commander Butch Wilmore exits the Starliner spacecraft Saturday following the scrubbed launch attempt.
A computer controlling the Atlas V rocket’s countdown triggered an automatic hold less than four minutes prior to liftoff of Boeing’s commercial Starliner spacecraft Saturday, keeping the crew test flight on the ground at least a few more days.
NASA astronauts Butch Wilmore and Suni Williams were already aboard the spacecraft when the countdown stopped due to a problem with a ground computer. “Hold. Hold. Hold,” a member of Atlas V launch team called out on an audio feed.
With the hold, the mission missed an instantaneous launch opportunity at 12: 25 pm EDT (16: 25 UTC), and later Saturday, NASA announced teams will forego a launch opportunity Sunday. The next chance to send Starliner into orbit will be 10: 52 am EDT (14: 52 UTC) Wednesday. The mission has one launch opportunity every one-to-two days, when the International Space Station’s orbital track moves back into proper alignment with the Atlas V rocket’s launch pad in Florida.
Wilmore and Williams will take the Starliner spacecraft on its first crew flight into low-Earth orbit. The capsule will dock with the International Space Station around a day after launch, spend at least a week there, then return to a parachute-assisted landing at one of two landing zones in New Mexico or Arizona. Once operational, Boeing’s Starliner will join SpaceX’s Crew Dragon capsule to give NASA two independent human-rated spacecraft for transporting astronauts to and from the space station.
It’s been a long road to get here with the Starliner spacecraft, and there’s more work to do before the capsule’s long-delayed first flight with astronauts.
Technicians from United Launch Alliance, builder of the Atlas V rocket, will begin troubleshooting the computer glitch at the launch pad Saturday evening, after draining propellant from the launch vehicle. Early indications suggest that a card in one of three computers governing the final minutes of the Atlas V’s countdown didn’t boot up as quickly as anticipated.
“You can imagine a large rack that is a big computer where the functions of the computer as a controller are broken up separately into individual cards or printed wire circuit boards with their logic devices,” said Tory Bruno, ULA’s president and CEO. “They’re all standalone, but together it’s an integrated controller.”
The computers are located at the launch pad inside a shelter near the base of the Atlas V rocket at Cape Canaveral Space Force Station. All three computers must be fully functioning in the final phase of the countdown to ensure triple redundancy. At the moment of liftoff, these computers control things like retracting umbilical lines and releasing bolts holding the rocket to its mobile launch platform.
Two of the computers activated as the final countdown sequence began at T-minus 4 minutes. A single card in the third computer took about six more seconds to come online, although it did boot up eventually, Bruno said.
“Two came up normally and the third one came up, but it was slow to come up, and that tripped a red line,” he said.
A disappointment
Wilmore and Williams, both veteran astronauts and former US Navy test pilots, exited the Starliner spacecraft with the help of Boeing’s ground team. They returned to NASA crew quarters at the nearby Kennedy Space Center to wait for the next launch attempt.
The schedule for the next try will depend on what ULA workers find when they access the computers at the launch pad. Officials initially said they could start another launch countdown early Sunday if they found a simple solution to the computer problem, such as swapping out a faulty card. The computers are networked together, but the architecture is designed with replaceable cards, each responsible for different functions during the countdown, to allow for a quick fix without having to replace the entire unit, Bruno said.
Enlarge/ United Launch Alliance’s Atlas V rocket and Boeing’s Starliner spacecraft at Cape Canaveral Space Force Station, Florida.
Later Saturday, NASA announced the launch won’t happen Sunday, giving teams additional time to assess the computer issue. The next launch opportunities are Wednesday and Thursday.
Bruno said ULA’s engineers suspect a hardware problem or a network communication glitch caused the computer issue during Saturday’s countdown. That is what ULA’s troubleshooting team will try to determine overnight. NASA said officials will share another update Sunday.
If it doesn’t get off the ground by Thursday, the Starliner test flight could face a longer delay to allow time for ULA to change out limited-life batteries on the Atlas V rocket. Bruno said the battery swap would take about 10 days.
Saturday’s aborted countdown was the latest in a string of delays for Boeing’s Starliner program. The spacecraft’s first crew test flight is running seven years behind the schedule Boeing announced when NASA awarded the company a $4.2 billion contract for the crew capsule in 2014. Put another way, Boeing has arrived at this moment nine years after the company originally said the spacecraft could be operational, when the program was first announced in 2010.
“Of course, this is emotionally disappointing,” said Mike Fincke, a NASA astronaut and a backup to Wilmore and Williams on the crew test flight. “I know Butch and Suni didn’t sound disappointed when we heard them on the loops, and it’s because it comes back to professionalism.”
NASA and Boeing were on the cusp of launching the Starliner test flight May 6, but officials called off the launch attempt due to a valve problem on the Atlas V rocket. Engineers later discovered a helium leak on the Starliner spacecraft’s service module, but managers agreed to proceed with the launch Saturday if the leak did not worsen during the countdown.
A check of the helium system Saturday morning showed the leak rate had decreased from a prior measurement, and it was no longer a constraint to launch. Instead, a different problem emerged to keep Starliner on Earth.
“Everybody is a little disappointed, but you kind of roll your sleeves up and get right back to work,” said Steve Stich, manager of NASA’s commercial crew program.
Enlarge/ Boeing’s Starliner spacecraft sits on top of a United Launch Alliance Atlas V rocket at Cape Canaveral Space Force Station, Florida.
NASA and Boeing officials are ready for a second attempt to launch the first crew test flight on the Starliner spacecraft Saturday from Cape Canaveral Space Force Station, Florida.
Liftoff of Boeing’s Starliner capsuled atop a United Launch Alliance Atlas V rocket is set for 12: 25 pm EDT (16: 25 UTC). NASA commander Butch Wilmore and pilot Suni Williams, both veteran astronauts, will take the Starliner spacecraft on its first trip into low-Earth orbit with a crew on board.
You can watch NASA TV’s live coverage of the countdown and launch below.
The first crew flight on a new spacecraft is not an everyday event. Starliner is the sixth orbital-class crew spacecraft in the history of the US space program, following Mercury, Gemini, Apollo, the space shuttle, and SpaceX’s Crew Dragon. NASA signed a $4.2 billion contract with Boeing in 2014 to develop Starliner, but the project is running years behind schedule and has cost Boeing nearly $1.5 billion in cost overruns. SpaceX, meanwhile, won a contract at the same time as Boeing and started launching astronauts on the Crew Dragon four years ago this week.
Now, it is finally Starliner’s turn. A successful crew test flight would set the stage for six operational Starliner flights to ferry astronauts to and from the International Space Station (ISS).
Assuming the test flight gets off the ground Saturday, the spacecraft is due for docking at the ISS at 1: 50 pm EDT (17: 50 UTC) Sunday to begin a stay of at least eight days. Once managers are satisfied the mission has achieved all its planned test objectives, and pending good weather conditions in Starliner’s landing zone in the western United States, the spacecraft will depart the station and return to Earth for a parachute-assisted touchdown. If the mission takes off on Saturday, the earliest nominal landing date would be Monday, June 10.
Wilmore and Williams have been here before. On May 6, the astronauts were strapped into their seats inside Starliner’s cockpit awaiting takeoff on a flight to the International Space Station. A valve malfunction on the Atlas V rocket prevented launch that day, and officials subsequently discovered a helium leak on Starliner’s service module that delayed the mission until this weekend.
Flying as-is
After weeks of reviews and analysis, managers determined Starliner is safe to fly as-is with the leak. The spacecraft uses helium gas to pressurize its propulsion system and push hydrazine and nitrogen tetroxide propellants from internal tanks to the capsule’s maneuvering thrusters.
“When we looked at this problem, it didn’t come down to trades,” said Mark Nappi, Boeing’s vice president and program manager for Starliner. “It came down to: Is it safe or not? And it is safe, and that is why we determined that we can fly with what we have.”
Ground teams traced the leak to a flange on one of four doghouse-shaped propulsion pods around the perimeter of the Starliner spacecraft’s service module. In a worst-case scenario, if the condition grew worse during the flight, ground controllers could isolate it by closing the manifold feeding the leak. If the leak doesn’t worsen, engineers are confident they can manage it with no major impacts to the mission.
“We looked really hard at what our options were with this particular flange,” said Steve Stich, manager of NASA’s commercial crew program, which oversees the agency’s contract with Boeing. The flange has a helium conduit and lines for the spacecraft’s toxic fuel and oxidizer, which makes a repair “problematic,” Stich said.
Enlarge/ Starliner commander Butch Wilmore and pilot Suni Williams arrived back at NASA’s Kennedy Space Center earlier this week to prepare for launch.
In order to safely fix the leak, which officials believe is likely caused by a defective seal, ground teams would have to disconnect the capsule from the Atlas V rocket, take it back to a hangar, drain its propellant tanks. This would probably push back the long-delayed Starliner test flight until late this year.
But the leak is relatively small and stable. “It’s about a half-pound per day out of 50 pounds of total capability in the tank,” Stich said.
“In our case, we have margin in the helium tank, and we’ve looked really hard to understand that margin and to understand the worst cases, and we took the time to go through that data,” Stich said. “We really think we can manage this leak, both by looking at it before the launch, and then if it got bigger in flight, we could manage it.”
Enlarge/ Boeing’s Starliner spacecraft atop its Atlas V rocket on the launch pad earlier this month.
Senior managers from NASA and Boeing told reporters on Friday that they plan to launch the first crew test flight of the Starliner spacecraft as soon as June 1, following several weeks of detailed analysis of a helium leak and a “design vulnerability” with the ship’s propulsion system.
Extensive data reviews over the last two-and-a-half weeks settled on a likely cause of the leak, which officials described as small and stable. During these reviews, engineers also built confidence that even if the leak worsened, it would not add any unacceptable risk for the Starliner test flight to the International Space Station, officials said.
But engineers also found that an unlikely mix of technical failures in Starliner’s propulsion system—representing 0.77 percent of all possible failure modes, according to Boeing’s program manager—could prevent the spacecraft from conducting a deorbit burn at the end of the mission.
“As we studied the helium leak, we also looked across the rest of the propulsion system, just to make sure we didn’t have any other things that we should be concerned about,” said Steve Stich, manager of NASA’s commercial crew program, which awarded a $4.2 billion contract to Boeing in 2014 for development of the Starliner spacecraft.
“We found a design vulnerability… in the prop [propulsion] system as we analyzed this particular helium leak, where for certain failure cases that are very remote, we didn’t have the capability to execute the deorbit burn with redundancy,” Stich said in a press conference Friday.
These two problems, uncovered one after the other, have kept the Starliner test flight grounded to allow time for engineers to find workarounds. This is the first time astronauts will fly into orbit on a Starliner spacecraft, following two unpiloted demonstration missions in 2019 and 2022.
The Starliner program is running years behind schedule, primarily due to problems with the spacecraft’s software, parachutes, and propulsion system, supplied by Aerojet Rocketdyne. Software woes cut short Starliner’s first test flight in 2019 before it could dock at the International Space Station, and they forced Boeing to fly an unplanned second test flight to gain confidence that the spacecraft is safe enough for astronauts. NASA and Boeing delayed the second unpiloted test flight nearly a year to overcome an issue with corroded valves in the ship’s propulsion system.
Last year, just a couple of months before it was supposed to launch on the crew test flight, officials discovered a design problem with Starliner’s parachutes and found that Boeing installed flammable tape inside the capsule’s cockpit. Boeing’s star-crossed Starliner finally appeared ready to fly on the long-delayed crew test flight from Cape Canaveral Space Force Station, Florida.
NASA commander Butch Wilmore and pilot Suni Williams were strapped into their seats inside Starliner on May 6 when officials halted the countdown due to a faulty valve on the spacecraft’s United Launch Alliance Atlas V rocket. ULA rolled the rocket back to its hangar to replace the valve, with an eye toward another launch attempt in mid-May.
But ground teams detected the helium leak in Starliner’s service module in the aftermath of the scrubbed countdown. After some initial troubleshooting, the leak rate grew to approximately 70 psi per minute. Since then, the leak rate has stabilized.
“That gave us pause as the leak rate grew, and we wanted to understand what was causing that leak,” Stich said.
Enlarge/ Boeing’s Starliner spacecraft on the eve of the first crew launch attempt earlier this month.
Miguel J. Rodriguez Carrillo/AFP via Getty Images
The first crewed test flight of Boeing’s long-delayed Starliner spacecraft won’t take off as planned Saturday and could face a longer postponement as engineers evaluate a stubborn leak of helium from the capsule’s propulsion system.
NASA announced the latest delay of the Starliner test flight late Tuesday. Officials will take more time to consider their options for how to proceed with the mission after discovering the small helium leak on the spacecraft’s service module.
The space agency did not describe what options are on the table, but sources said they range from flying the spacecraft “as is” with a thorough understanding of the leak and confidence it won’t become more significant in flight, to removing the capsule from its Atlas V rocket and taking it back to a hangar for repairs.
Theoretically, the former option could permit a launch attempt as soon as next week. The latter alternative could delay the launch until at least late summer.
“The team has been in meetings for two consecutive days, assessing flight rationale, system performance, and redundancy,” NASA said in a statement Tuesday night. “There is still forward work in these areas, and the next possible launch opportunity is still being discussed. NASA will share more details once we have a clearer path forward.”
Software problems cut short an unpiloted test flight in 2019, forcing Boeing to fly a second demonstration mission. Starliner was on the launch pad when pre-flight checkouts revealed stuck valves in the spacecraft’s propulsion system in 2021. Boeing finally flew Starliner on a round-trip mission to the space station in May 2022. Concerns about Starliner’s parachutes and flammable tape inside the spacecraft’s crew cabin delayed the crewed test flight from last summer until this year.
Boeing aims to become the second company to fly astronauts to the space station under contract with NASA’s commercial crew program, following the start of SpaceX’s crew transportation service in 2020. Assuming a smooth crewed test flight, NASA hopes to clear the Starliner spacecraft for six-month crew rotation flights to the space station beginning next year.
In the doghouse
Engineers first noticed the helium leak during the first launch attempt for Starliner’s crewed test flight May 6, but managers did not consider it significant enough to stop the launch. Ultimately, a separate problem with a pressure regulation valve on the spacecraft’s United Launch Alliance (ULA) Atlas V rocket prompted officials to scrub the launch attempt.
NASA astronauts Butch Wilmore and Suni Williams were already strapped into their seats inside the Starliner spacecraft on the launch pad at Cape Canaveral Space Force Station, Florida, when officials ordered a halt to the May 6 countdown. Wilmore and Williams returned to their homes in Houston to await the next Starliner launch opportunity.
ULA returned the Atlas V rocket to its hangar, where technicians swapped out the faulty valve in time for another launch attempt May 17. NASA and Boeing pushed the launch date back to May 21, then to May 25, as engineers assessed the helium leak. The Atlas V rocket and Starliner spacecraft remain inside ULA’s Vertical Integration Facility to wait for the next launch opportunity.
Boeing engineers traced the leak to a flange on a single reaction control system thruster in one of four doghouse-shaped propulsion pods on the Starliner service module.
There are 28 reaction control system thrusters—essentially small rocket engines—on the Starliner service module. In orbit, these thrusters are used for minor course corrections and pointing the spacecraft in the proper direction. The service module has two sets of more powerful engines for larger orbital adjustments and launch-abort maneuvers.
The spacecraft’s propulsion system is pressurized using helium, an inert gas. The thrusters burn a mixture of toxic hydrazine and nitrogen tetroxide propellants. Helium is not combustible, so a small leak is not likely to be a major safety issue on the ground. However, the system needs sufficient helium gas to force propellants from their internal storage tanks to Starliner’s thrusters.
In a statement last week, NASA described the helium leak as “stable” and said it would not pose a risk to the Starliner mission if it didn’t worsen. A Boeing spokesperson declined to provide Ars with any details about the helium leak rate.
If NASA and Boeing resolve their concerns about the helium leak without requiring lengthy repairs, the International Space Station could accommodate the docking of Starliner through part of July. After docking at the station, Wilmore and Williams will spend at least eight days at the complex before undocking to head for a parachute-assisted, airbag-cushioned landing in the Southwestern United States.
After July, the schedule gets messy.
The space station has a busy slate of multiple visiting crew and cargo vehicles in August, including the arrival of a fresh team of astronauts on a SpaceX Dragon spacecraft and the departure of an outgoing crew on another Dragon. There may be an additional window for Starliner to dock with the space station in late August or early September before the launch of SpaceX’s next cargo mission, which will occupy the docking port Starliner needs to use. The docking port opens up again in the fall.
ULA also has other high-priority missions it would like to launch from the same pad needed for the Starliner test flight. Later this summer, ULA plans to launch a US Space Force mission; it will be the last mission to use an Atlas V rocket. Then, ULA aims to launch the second demonstration flight of its new Vulcan Centaur rocket—the Atlas V’s replacement—as soon as September.
Enlarge/ SpaceX’s Starship tower (left) at Launch Complex 39A dwarfs the launch pad for the Falcon 9 rocket (right).
There are a couple of ways to read the announcement from the Federal Aviation Administration that it’s kicking off a new environmental review of SpaceX’s plan to launch the most powerful rocket in the world from Florida.
The FAA said on May 10 that it plans to develop an Environmental Impact Statement (EIS) for SpaceX’s proposal to launch Starships from NASA’s Kennedy Space Center in Florida. The FAA ordered this review after SpaceX updated the regulatory agency on the projected Starship launch rate and the design of the ground infrastructure needed at Launch Complex 39A (LC-39A), the historic launch pad once used for Apollo and Space Shuttle missions.
Dual environmental reviews
At the same time, the US Space Force is overseeing a similar EIS for SpaceX’s proposal to take over a launch pad at Cape Canaveral Space Force Station, a few miles south of LC-39A. This launch pad, designated Space Launch Complex 37 (SLC-37), is available for use after United Launch Alliance’s last Delta rocket lifted off there in April.
On the one hand, these environmental reviews often take a while and could cloud Elon Musk’s goal of having Starship launch sites in Florida ready for service by the end of 2025. “A couple of years would not be a surprise,” said George Nield, an aerospace industry consultant and former head of the FAA’s Office of Commercial Space Transportation.
Another way to look at the recent FAA and Space Force announcements of pending environmental reviews is that SpaceX finally appears to be cementing its plans to launch Starship from Florida. These plans have changed quite a bit in the last five years.
The environmental reviews will culminate in a decision on whether to approve SpaceX’s proposals for Starship launches at LC-39A and SLC-37. The FAA will then go through a separate licensing process, similar to the framework used to license the first three Starship test launches from South Texas.
NASA has contracts with SpaceX worth more than $4 billion to develop a human-rated version of Starship to land astronauts on the Moon on the first two Artemis lunar landing flights later this decade. To do that, SpaceX must stage a fuel depot in low-Earth orbit to refuel the Starship lunar lander before it heads for the Moon. It will take a series of Starship tanker flights—perhaps 10 to 15—to fill the depot with cryogenic propellants.
Launching that many Starships over the course of a month or two will require SpaceX to alternate between at least two launch pads. NASA and SpaceX officials say the best way to do this is by launching Starships from one pad in Texas and another in Florida.
Earlier this week, Ars spoke with Lisa Watson-Morgan, who manages NASA’s human-rated lunar lander program. She was at Kennedy Space Center this week for briefings on the Starship lander and a competing lander from Blue Origin. One of the topics, she said, was the FAA’s new environmental review before Starship can launch from LC-39A.
“I would say we’re doing all we can to pull the schedule to where it needs to be, and we are working with SpaceX to make sure that their timeline, the EIS timeline, and NASA’s all work in parallel as much as we can to achieve our objectives,” she said. “When you’re writing it down on paper just as it is, it looks like there could be some tight areas, but I would say we’re collectively working through it.”
Officially, SpaceX plans to perform a dress rehearsal for the Starship lunar landing in late 2025. This will be a full demonstration, with refueling missions, an uncrewed landing of Starship on the lunar surface, then a takeoff from the Moon, before NASA commits to putting people on Starship on the Artemis III mission, currently slated for September 2026.
So you can see that schedules are already tight for the Starship lunar landing demonstration if SpaceX activates launch pads in Florida late next year.
Enlarge/ Riding atop a SpaceX Falcon 9 rocket, NASA’s Double Asteroid Redirection Test, or DART, spacecraft sets off to collide with an asteroid in the world’s first full-scale planetary defense test mission in November 2021.
On a fall evening in 2022, scientists at the Johns Hopkins University Applied Physics Laboratory were busy with the final stages of a planetary defense mission. As Andy Rivkin, one of the team leaders, was getting ready to appear in NASA’s live broadcast of the experiment, a colleague posted a photo of a pair of asteroids: the half-mile-wide Didymos and, orbiting around it, a smaller one called Dimorphos, taken about 7 million miles from Earth.
“We were able to see Didymos and this little dot in the right spot where we expected Dimorphos to be,” Rivkin recalled.
After the interview, Rivkin joined a crowd of scientists and guests to watch the mission’s finale on several big screens: As part of an asteroid deflection mission called DART, a spacecraft was closing in on Dimorphos and photographing its rocky surface in increasing detail.
Then, at 7: 14 pm, a roughly 1,300-pound spacecraft slammed head-on into the asteroid.
Within a few minutes, members of the mission team in Kenya and South Africa posted images from their telescopes, showing a bright plume of debris.
In the days that followed, researchers continued to observe the dust cloud and discovered it had morphed into a variety of shapes, including clumps, spirals, and two comet-like tails. They also calculated that the impact slowed Dimorphos’ orbit by about a tenth of an inch per second, proof-of-concept that a spacecraft—also called a kinetic impactor—could target and deflect an asteroid far from Earth.
The final five-and-a-half minutes of images from the DART spacecraft as it approached and then intentionally collided with asteroid Dimorphos. The video is 10 times faster than reality, except for the last six images.
NASA/Johns Hopkins APL/YouTube
Ron Ballouz, a planetary scientist at the lab, commented that what is often seen in the movies is a “sort of last-ditch-effort, what we like to call a final-stage of planetary defense.” But if hazardous objects can be detected years in advance, other techniques like a kinetic impactor can be used, he added.
If a deflection were necessary, scientists would need to change the speed of a hazardous object, such as an asteroid or comet, enough that it doesn’t end up at the same place and time as Earth as they orbit the Sun. Rivkin said this translates into at least a seven-minute change in the arrival time: If a Dimorphos-sized object were predicted to collide with Earth 67 years from now, for instance, the slow-down that DART imparted would be just enough to add up to the seven minutes, he added.
With less lead time, researchers could use a combination of multiple deflections, larger spacecrafts, or boosts in speed, depending on the hazardous object. “DART was designed to validate a technique, and specific situations would inevitably require adapting things,” said Rivkin.
Researchers use data from DART and smaller-scale experiments to predict the amount of deflection using computer simulations.
Scientists are also focusing on the type of asteroid that Dimorphos appears to be: a “rubble pile,” as they call it, because objects of this kind are thought to be made of clumps of many rocks.
In fact, scientists think that most asteroids the size of Dimorphos and larger are rubble piles. As scientists continue to learn more about rubble piles, they will be able to make better predictions about deflecting asteroids or comets. And in 2026, a new mission will arrive at Didymos and Dimorphos to collect more data to fine-tune the computer models.
In the meantime, researchers are trying to learn as much as possible in the unwelcome case an asteroid or comet is discovered to be a threat to Earth and a more rapid response is necessary.
Scientists first suspected that many asteroids are rubble piles about 50 years ago. Their models showed that when larger asteroids smashed into one another, the collisions could throw off fragments that would then reassemble to form new objects.
It wasn’t until 2005, though, that scientists saw their first rubble pile: asteroid Itokawa, when a spacecraft visited it and photographed it. Then, in 2018, they saw another called Ryugu, and later that year, one more, asteroid Bennu. DART’s camera also showed Didymos and Dimorphos are likely of the same variety.
“It’s one thing to talk about rubble piles, but another to see what looks like a bunch of rocks dumped off a truck up close,” said William Bottke, a planetary scientist at the Southwest Research Institute in Boulder, Colorado.
Enlarge/ The Orion spacecraft after splashdown in the Pacific Ocean at the end of the Artemis I mission.
NASA has asked a panel of outside experts to review the agency’s investigation into the unexpected loss of material from the heat shield of the Orion spacecraft on a test flight in 2022.
Chunks of charred material cracked and chipped away from Orion’s heat shield during reentry at the end of the 25-day unpiloted Artemis I mission in December 2022. Engineers inspecting the capsule after the flight found more than 100 locations where the stresses of reentry stripped away pieces of the heat shield as temperatures built up to 5,000° Fahrenheit.
This was the most significant discovery on the Artemis I, an unpiloted test flight that took the Orion capsule around the Moon for the first time. The next mission in NASA’s Artemis program, Artemis II, is scheduled for launch late next year on a test flight to send four astronauts around the far side of the Moon.
Another set of eyes
The heat shield, made of a material called Avcoat, is attached to the base of the Orion spacecraft in 186 blocks. Avcoat is designed to ablate, or erode, in a controlled manner during reentry. Instead, fragments fell off the heat shield that left cavities resembling potholes.
Investigators are still looking for the root cause of the heat shield problem. Since the Artemis I mission, engineers conducted sub-scale tests of the Orion heat shield in wind tunnels and high-temperature arcjet facilities. NASA has recreated the phenomenon observed on Artemis I in these ground tests, according to Rachel Kraft, an agency spokesperson.
“The team is currently synthesizing results from a variety of tests and analyses that inform the leading theory for what caused the issues,” said Rachel Kraft, a NASA spokesperson.
Last week, nearly a year and a half after the Artemis I flight, the public got its first look at the condition of the Orion heat shield with post-flight photos released in a report from NASA’s inspector general. Cameras aboard the Orion capsule also recorded pieces of the heat shield breaking off the spacecraft during reentry.
NASA’s inspector general said the char loss issue “creates a risk that the heat shield may not sufficiently protect the capsule’s systems and crew from the extreme heat of reentry on future missions.”
“Those pictures, we’ve seen them since they were taken, but more importantly… we saw it,” said Victor Glover, pilot of the Artemis II mission, in a recent interview with Ars. “More than any picture or report, I’ve seen that heat shield, and that really set the bit for how interested I was in the details.”
