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.”
Enlarge/ The Atlas V rocket and Starliner spacecraft on their launch pad Monday.
Astronauts Butch Wilmore and Suni Williams climbed into their seats inside Boeing’s Starliner spacecraft Monday night in Florida, but trouble with the capsule’s Atlas V rocket kept the commercial ship’s long-delayed crew test flight on the ground.
Around two hours before launch time, shortly after 8: 30 pm EDT (00: 30 UTC), United Launch Alliance’s launch team stopped the countdown. “The engineering team has evaluated, the vehicle is not in a configuration where we can proceed with flight today,” said Doug Lebo, ULA’s launch conductor.
The culprit was a misbehaving valve on the rocket’s Centaur upper stage, which has two RL10 engines fed by super-cold liquid hydrogen and liquid oxygen propellants.
“We saw a self-regulating valve on the LOX (liquid oxygen) side had a bit of a buzz; it was moving in a strange behavior,” said Steve Stich, NASA’s commercial crew program manager. “The flight rules had been laid out for this flight ahead of time. With the crew at the launch pad, the proper action was to scrub.”
The next opportunity to launch Starliner on its first crew test flight will be Friday night at 9 pm EDT (01: 00 UTC Saturday). NASA announced overnight that officials decided to skip a launch opportunity Tuesday night to allow engineers more time to study the valve problem and decide whether they need to replace it.
Work ahead
Everything else was going smoothly in the countdown Monday night. This mission will also be the first time astronauts have flown on ULA’s Atlas V rocket, which has logged 99 successful flights since 2002. It is the culmination of nearly a decade-and-a-half of development by Boeing, which has a $4.2 billion contract with NASA to ready Starliner for crew missions, then carry out six long-duration crew ferry flights to and from the International Space Station.
This crew test flight will last at least eight days, taking Wilmore and Williams to the space station to verify Starliner’s readiness for operational missions. Once Starliner flies, NASA will have two human-rated spacecraft on contract. SpaceX’s Crew Dragon has been in service since 2020.
When officials scrubbed Monday night’s launch attempt, Wilmore and Williams were already aboard the Starliner spacecraft on top of the Atlas V rocket at Cape Canaveral Space Force Station, Florida. The Boeing and ULA support team helped them out of the capsule and drove them back to crew quarters at the nearby Kennedy Space Center to wait for the next launch attempt.
“I promised Butch and Suni a boring evening,” said Tory Bruno, ULA’s CEO. “I didn’t mean for it to be quite this boring, but we’re going to follow our rules, and we’re going to make sure that the crew is safe.”
When the next launch attempt actually occurs depends on whether ULA engineers determine they can resolve the problem without rolling the Atlas V rocket back to its hangar for repairs.
The valve in question vents gas from the liquid oxygen tank on the Centaur upper stage to maintain the tank at proper pressures. This is important for two reasons. The tank needs to be at the correct pressure for the RL10 engines to receive propellant during the flight, and the Centaur upper stage itself has ultra-thin walls to reduce weight, and requires pressure to maintain structural integrity.
Enlarge/ This image captured by Astroscale’s ADRAS-J satellite shows the discarded upper stage from a Japanese H-IIA rocket.
Welcome to Edition 6.42 of the Rocket Report! Several major missions are set for launch in the next few months. These include the first crew flight on Boeing’s Starliner spacecraft, set for liftoff on May 6, and the next test flight of SpaceX’s Starship rocket, which could happen before the end of May. Perhaps as soon as early summer, SpaceX could launch the Polaris Dawn mission with four private astronauts, who will perform the first fully commercial spacewalk in orbit. In June or July, Europe’s new Ariane 6 rocket is slated to launch for the first time. Rest assured, Ars will have it all covered.
As always, we welcome reader submissions, and if you don’t want to miss an issue, please subscribe using the box below (the form will not appear on AMP-enabled versions of the site). Each report will include information on small-, medium-, and heavy-lift rockets as well as a quick look ahead at the next three launches on the calendar.
German rocket arrives at Scottish spaceport. Rocket Factory Augsburg has delivered a booster for its privately developed RFA One rocket to SaxaVord Spaceport in Scotland, the company announced on X. The first stage for the RFA One rocket was installed on its launch pad at SaxaVord to undergo preparations for a static fire test. The booster arrived at the Scottish launch site with five of its kerosene-fueled Helix engines. The remaining four Helix engines, for a total of nine, will be fitted to the RFA One booster at SaxaVord, the company said.
Aiming to fly this year… RFA hopes to launch its first orbital-class rocket by the end of 2024. The UK’s Civil Aviation Authority last month granted a range license to SaxaVord Spaceport to allow the spaceport operator to control the sea and airspace during a launch. RFA is primarily privately funded but has won financial support from the European Space Agency, the UK Space Agency, and the German space agency, known as DLR. The RFA One rocket will have three stages, stand nearly 100 feet (30 meters) tall, and can carry nearly 2,900 pounds (1,300 kilograms) of payload into a polar Sun-synchronous orbit.
Arianespace wins ESA launch contract. The European Space Agency has awarded Arianespace a contract to launch a joint European-Chinese space science satellite in late 2025, European Spaceflight reports. The Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) is a 4,850-pound (2,200-kilogram) spacecraft that will study Earth’s magnetic environment on a global scale. The aim of the mission is to build a more complete understanding of the Sun-Earth connection. On Tuesday, ESA officially signed a contract for Arianespace to launch SMILE aboard a Vega C rocket, which is built by the Italian rocket-maker Avio.
But it may not keep it … In late 2023, ESA member states agreed to allow Avio to market and manage the launch of Vega C flights independent of Arianespace. When the deal was initially struck, 17 flights were contracted through Arianespace to be launched aboard Vega vehicles. While these missions are still managed by Arianespace, Avio is working with the launch provider to strike a deal that would allow the Italian rocket builder to assume the management of all Vega flights. The Vega C rocket has been grounded since a launch failure in 2022 forced Avio to redesign the nozzle of the rocket’s solid-fueled second-stage motor. Vega C is scheduled to return to flight before the end of 2024. (submitted by Ken the Bin)
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Update on ABL’s second launch. ABL Space Systems expected to launch its second light-class RS1 rocket earlier this year, but the company encountered an anomaly during ground testing at the launch site in Alaska, according to Aria Alamalhodaei of TechCrunch. Kevin Sagis, ABL’s chief engineer, said there is “no significant delay” in the launch of the second RS1 rocket, but the company has not announced a firm schedule. “During ground testing designed to screen the vehicle for flight, an issue presented that caused us to roll back to the hangar,” Sagis said, according to Alamalhodaei. “We have since resolved and dispositioned the issue. There was no loss of hardware and we have validated vehicle health back out on the pad. We are continuing with preparations for static fire and launch.”
Nearly 16 months without a launch … ABL’s first RS1 test flight in January 2023 ended seconds after liftoff with the premature shutdown of its liquid-fueled engines. The rocket crashed back onto its launch pad in Alaska. An investigation revealed a fire in the aft end of the RS1 booster burned through wiring harnesses, causing the rocket to lose power and shut off its engines. Engineers believe the rocket’s mobile launch mount was too small, placing the rocket too close to the ground when it ignited its engines. This caused the hot engine exhaust to recirculate under the rocket and led to a fire in the engine compartment as it took off.
Enlarge/ Artist’s illustration of two Starships docked belly-to-belly in orbit.
SpaceX
Some time next year, NASA believes SpaceX will be ready to link two Starships in orbit for an ambitious refueling demonstration, a technical feat that will put the Moon within reach.
SpaceX is under contract with NASA to supply two human-rated Starships for the first two astronaut landings on the Moon through the agency’s Artemis program, which aims to return people to the lunar surface for the first time since 1972. The first of these landings, on NASA’s Artemis III mission, is currently targeted for 2026, although this is widely viewed as an ambitious schedule.
Last year, NASA awarded a contract to Blue Origin to develop its own human-rated Blue Moon lunar lander, giving Artemis managers two options for follow-on missions.
Designers of both landers were future-minded. They designed Starship and Blue Moon for refueling in space. This means they can eventually be reused for multiple missions, and ultimately, could take advantage of propellants produced from resources on the Moon or Mars.
Amit Kshatriya, who leads the “Moon to Mars” program within NASA’s exploration division, outlined SpaceX’s plan to do this in a meeting with a committee of the NASA Advisory Council on Friday. He said the Starship test program is gaining momentum, with the next test flight from SpaceX’s Starbase launch site in South Texas expected by the end of May.
“Production is not the issue,” Kshatriya said. “They’re rolling cores out. The engines are flowing into the factory. That is not the issue. The issue is it is a significant development challenge to do what they’re trying to do … We have to get on top of this propellant transfer problem. It is the right problem to try and solve. We’re trying to build a blueprint for deep space exploration.”
Road map to refueling
Before getting to the Moon, SpaceX and Blue Origin must master the technologies and techniques required for in-space refueling. Right now, SpaceX is scheduled to attempt the first demonstration of a large-scale propellant transfer between two Starships in orbit next year.
There will be at least several more Starship test flights before then. During the most recent Starship test flight in March, SpaceX conducted a cryogenic propellant transfer test between two tanks inside the vehicle. This tank-to-tank transfer of liquid oxygen was part of a demonstration supported with NASA funding. Agency officials said this demonstration would allow engineers to learn more about how the fluid behaves in a low-gravity environment.
Kshatriya said that while engineers are still analyzing the results of the cryogenic transfer demonstration, the test on the March Starship flight “was successful by all accounts.”
“That milestone is behind them,” he said Friday. Now, SpaceX will move out with more Starship test flights. The next launch will try to check off a few more capabilities SpaceX didn’t demonstrate on the March test flight.
These will include a precise landing of Starship’s Super Heavy booster in the Gulf of Mexico, which is necessary before SpaceX tries to land the booster back at its launch pad in Texas. Another objective will likely be the restart of a single Raptor engine on Starship in flight, which SpaceX didn’t accomplish on the March flight due to unexpected roll rates on the vehicle as it coasted through space. Achieving an in-orbit engine restart—necessary to guide Starship toward a controlled reentry—is a prerequisite for future launches into a stable higher orbit, where the ship could loiter for hours, days, or weeks to deploy satellites and attempt refueling.
In the long run, SpaceX wants to ramp up the Starship launch cadence to many daily flights from multiple launch sites. To achieve that goal, SpaceX plans to recover and rapidly reuse Starships and Super Heavy boosters, building on expertise from the partially reusable Falcon 9 rocket. Elon Musk, SpaceX’s founder and CEO, is keen on reusing ships and boosters as soon as possible. Earlier this month, Musk said he is optimistic SpaceX can recover a Super Heavy booster in Texas later this year and land a Starship back in Texas sometime next year.
Enlarge/ NASA’s Orion spacecraft descends toward the Pacific Ocean on December 11, 2021, at the end of the Artemis I mission.
NASA
NASA officials declared the Artemis I mission successful in late 2021, and it’s hard to argue with that assessment. The Space Launch System rocket and Orion spacecraft performed nearly flawlessly on an unpiloted flight that took it around the Moon and back to Earth, setting the stage for the Artemis II, the program’s first crew mission.
But one of the things engineers saw on Artemis I that didn’t quite match expectations was an issue with the Orion spacecraft’s heat shield. As the capsule streaked back into Earth’s atmosphere at the end of the mission, the heat shield ablated, or burned off, in a different manner than predicted by computer models.
More of the charred material than expected came off the heat shield during the Artemis I reentry, and the way it came off was somewhat uneven, NASA officials said. Orion’s heat shield is made of a material called Avcoat, which is designed to burn off as the spacecraft plunges into the atmosphere at 25,000 mph (40,000 km per hour). Coming back from the Moon, Orion encountered temperatures up to 5,000° Fahrenheit (2,760° Celsius), hotter than a spacecraft sees when it reenters the atmosphere from low-Earth orbit.
Despite heat shield issue, the Orion spacecraft safely splashed down in the Pacific Ocean. Engineers discovered the uneven charring during post-flight inspections.
No answers yet
Amit Kshatriya, who oversees development for the Artemis missions in NASA’s exploration division, said Friday that the agency is still looking for the root cause of the heat shield issue. Managers want to be sure they understand the cause before proceeding with Artemis II, which will send astronauts Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen on a 10-day flight around the far side of the Moon.
This will be the first time humans fly near the Moon since the last Apollo mission in 1972. In January, NASA announced a delay in the launch of Artemis II from late 2024 until September 2025, largely due to the unresolved investigation into the heat shield issue.
“We are still in the middle of our investigation on the performance of the heat shield from Artemis I,” Kshatriya said Friday in a meeting with a committee of the NASA Advisory Council.
Engineers have performed sub-scale heat shield tests in wind tunnels and arc jet facilities to better understand what led to the uneven charring on Artemis I. “We’re getting close to the final answer in terms of that cause,” Kshatriya said.
NASA officials previously said it is unlikely they will need to make changes to the heat shield already installed on the Orion spacecraft for Artemis II, but haven’t ruled it out. A redesign or modifications to the Orion heat shield on Artemis II would probably delay the mission by at least a year.
Instead, engineers are analyzing all of the possible trajectories the Orion spacecraft could fly when it reenters the atmosphere at the end of the Artemis II mission. On Artemis I, Orion flew a skip reentry profile, where it dipped into the atmosphere, skipped back into space, and then made a final descent into the atmosphere, sort of like a rock skipping across a pond. This profile allows Orion to make more precise splashdowns near recovery teams in the Pacific Ocean and reduces g-forces on the spacecraft and the crew riding inside. It also splits up the heat load on the spacecraft into two phases.
The Apollo missions flew a direct reentry profile. There is also a reentry mode available called a ballistic entry, in which the spacecraft would fly through the atmosphere unguided.
Enlarge/ Ground teams at NASA’s Kennedy Space Center in Florida moved the Orion spacecraft for the Artemis II mission into an altitude chamber earlier this month.
The charred material began flying off the heat shield in the first phase of the skip reentry. Engineers are looking at how the skip reentry profile affected the performance of the Orion heat shield. NASA wants to understand how the Orion heat shield would perform during each of the possible reentry trajectories for Artemis II.
“What we have the analysis teams off doing is saying, ‘OK, independent of what the constraints are going to be, what can we tolerate?” Kshatriya said.
Once officials understand the cause of the heat shield charring, engineers will determine what kind of trajectory Artemis II needs to fly on reentry to minimize risk to the crew. Then, managers will look at building what NASA calls flight rationale. Essentially, this is a process of convincing themselves the spacecraft is safe to fly.
“When we stitch it all together, we’ll either have flight rationale or we won’t,” Kshatriya said.
Assuming NASA approves the flight rationale for Artemis II, there will be additional discussions about how to ensure Orion heat shields are safe to fly on downstream Artemis missions, which will have higher-speed reentry profiles as astronauts return from landings on the Moon.
In the meantime, preparations on the Orion spacecraft for Artemis II continue at NASA’s Kennedy Space Center. The crew and service modules for Artemis II were mated together earlier this year, and the entire Orion spacecraft is now inside a vacuum chamber for environmental testing.
Enlarge/ A Voyager space probe in a clean room at the Jet Propulsion Laboratory in 1977.
Engineers have determined why NASA’s Voyager 1 probe has been transmitting gibberish for nearly five months, raising hopes of recovering humanity’s most distant spacecraft.
Voyager 1, traveling outbound some 15 billion miles (24 billion km) from Earth, started beaming unreadable data down to ground controllers on November 14. For nearly four months, NASA knew Voyager 1 was still alive—it continued to broadcast a steady signal—but could not decipher anything it was saying.
Confirming their hypothesis, engineers at NASA’s Jet Propulsion Laboratory (JPL) in California confirmed a small portion of corrupted memory caused the problem. The faulty memory bank is located in Voyager 1’s Flight Data System (FDS), one of three computers on the spacecraft. The FDS operates alongside a command-and-control central computer and another device overseeing attitude control and pointing.
The FDS duties include packaging Voyager 1’s science and engineering data for relay to Earth through the craft’s Telemetry Modulation Unit and radio transmitter. According to NASA, about 3 percent of the FDS memory has been corrupted, preventing the computer from carrying out normal operations.
Optimism growing
Suzanne Dodd, NASA’s project manager for the twin Voyager probes, told Ars in February that this was one of the most serious problems the mission has ever faced. That is saying something because Voyager 1 and 2 are NASA’s longest-lived spacecraft. They launched 16 days apart in 1977, and after flying by Jupiter and Saturn, Voyager 1 is flying farther from Earth than any spacecraft in history. Voyager 2 is trailing Voyager 1 by about 2.5 billion miles, although the probes are heading out of the Solar System in different directions.
Normally, engineers would try to diagnose a spacecraft malfunction by analyzing data it sent back to Earth. They couldn’t do that in this case because Voyager 1 has been transmitting data packages manifesting a repeating pattern of ones and zeros. Still, Voyager 1’s ground team identified the FDS as the likely source of the problem.
The Flight Data Subsystem was an innovation in computing when it was developed five decades ago. It was the first computer on a spacecraft to use volatile memory. Most of NASA’s missions operate with redundancy, so each Voyager spacecraft launched with two FDS computers. But the backup FDS on Voyager 1 failed in 1982.
Due to the Voyagers’ age, engineers had to reference paper documents, memos, and blueprints to help understand the spacecraft’s design details. After months of brainstorming and planning, teams at JPL uplinked a command in early March to prompt the spacecraft to send back a readout of the FDS memory.
The command worked, and Voyager.1 responded with a signal different from the code the spacecraft had been transmitting since November. After several weeks of meticulous examination of the new code, engineers pinpointed the locations of the bad memory.
“The team suspects that a single chip responsible for storing part of the affected portion of the FDS memory isn’t working,” NASA said in an update posted Thursday. “Engineers can’t determine with certainty what caused the issue. Two possibilities are that the chip could have been hit by an energetic particle from space or that it simply may have worn out after 46 years.”
Voyager 1’s distance from Earth complicates the troubleshooting effort. The one-way travel time for a radio signal to reach Voyager 1 from Earth is about 22.5 hours, meaning it takes roughly 45 hours for engineers on the ground to learn how the spacecraft responded to their commands.
NASA also must use its largest communications antennas to contact Voyager 1. These 230-foot-diameter (70-meter) antennas are in high demand by many other NASA spacecraft, so the Voyager team has to compete with other missions to secure time for troubleshooting. This means it will take time to get Voyager 1 back to normal operations.
“Although it may take weeks or months, engineers are optimistic they can find a way for the FDS to operate normally without the unusable memory hardware, which would enable Voyager 1 to begin returning science and engineering data again,” NASA said.
Enlarge/ This cylindrical object, a few inches in size, fell through the roof of Alejandro Otero’s home in Florida last month.
A few weeks ago, something from the heavens came crashing through the roof of Alejandro Otero’s home, and NASA is on the case.
In all likelihood, this nearly two-pound object came from the International Space Station. Otero said it tore through the roof and both floors of his two-story house in Naples, Florida.
Otero wasn’t home at the time, but his son was there. A Nest home security camera captured the sound of the crash at 2: 34 pm local time (19: 34 UTC) on March 8. That’s an important piece of information because it is a close match for the time—2: 29 pm EST (19: 29 UTC)—that US Space Command recorded the reentry of a piece of space debris from the space station. At that time, the object was on a path over the Gulf of Mexico, heading toward southwest Florida.
This space junk consisted of depleted batteries from the ISS, attached to a cargo pallet that was originally supposed to come back to Earth in a controlled manner. But a series of delays meant this cargo pallet missed its ride back to Earth, so NASA jettisoned the batteries from the space station in 2021 to head for an unguided reentry.
Otero’s likely encounter with space debris was first reported by WINK News, the CBS affiliate for southwest Florida. Since then, NASA has recovered the debris from the homeowner, according to Josh Finch, an agency spokesperson.
Engineers at NASA’s Kennedy Space Center will analyze the object “as soon as possible to determine its origin,” Finch told Ars. “More information will be available once the analysis is complete.”
Ars reported on this reentry when it happened on March 8, noting that most of the material from the batteries and the cargo carrier would have likely burned up as they plunged through the atmosphere. Temperatures would have reached several thousand degrees, vaporizing most of the material before it could reach the ground.
The entire pallet, including the nine disused batteries from the space station’s power system, had a mass of more than 2.6 metric tons (5,800 pounds), according to NASA. Size-wise, it was about twice as tall as a standard kitchen refrigerator. It’s important to note that objects of this mass, or larger, regularly fall to Earth on guided trajectories, but they’re usually failed satellites or spent rocket stages left in orbit after completing their missions.
In a post on X, Otero said he is waiting for communication from “the responsible agencies” to resolve the cost of damages to his home.
Hello. Looks like one of those pieces missed Ft Myers and landed in my house in Naples. Tore through the roof and went thru 2 floors. Almost his my son. Can you please assist with getting NASA to connect with me? I’ve left messages and emails without a response. pic.twitter.com/Yi29f3EwyV
If the object is owned by NASA, Otero or his insurance company could make a claim against the federal government under the Federal Tort Claims Act, according to Michelle Hanlon, executive director of the Center for Air and Space Law at the University of Mississippi.
“It gets more interesting if this material is discovered to be not originally from the United States,” she told Ars. “If it is a human-made space object which was launched into space by another country, which caused damage on Earth, that country would be absolutely liable to the homeowner for the damage caused.”
This could be an issue in this case. The batteries were owned by NASA, but they were attached to a pallet structure launched by Japan’s space agency.
Enlarge/ NASA’s and Lockheed Martin’s X-59 experimental supersonic jet is unveiled during a ceremony in Palmdale, California, on January 12, 2024.
Robyn Beck/AFP via Getty Images
When Chuck Yeager reached Mach 1 on October 14, 1947, the entire frame of his Bell X-1 aircraft suddenly started to shake, and the controls went. A crew observing the flight in a van on the ground reported hearing something like a distant, rolling thunder. They were probably the first people on Earth to hear a boom made by a supersonic aircraft.
The boom felt like an innocent curiosity at first but soon turned into a nightmare. In no time, supersonic jets—F-100 Super Sabers, F-101 Voodoos, and B-58 Hustlers—came to Air Force bases across the US, and with them came the booms. Proper, panes-flying-off-the windows supersonic booms. People filed over 40,000 complaints about nuisance and property damage caused by booming jets, which eventually ended up with the Federal Aviation Administration imposing a Mach 1 speed limit for flights over land in 1973.
Now, NASA wants this ban to go. It has started the Quesst mission to go fast over American cities once more. But this time, it wants to do it quietly.
Breaking the sound barrier
The reason Yeager’s X-1 was so difficult to control at Mach 1 was not an actual “sound barrier” the plane broke. The “barrier” aspect is purely metaphorical. While Yeager’s plane experienced turbulence and shaking, it was due to rising drag and aircraft design.
At subsonic speeds, the airflow around the wings, tail, and fuselage is smooth. But at supersonic speeds, the air going over irregular shapes— the nose, canopy, and wings—accelerates to above the speed of sound. Then, where the curvature of the wing or canopy becomes less pronounced, it starts to build up pressure and decelerate back below Mach 1, a phenomenon known as “adverse pressure.” This creates shockwaves, and those are what cause supersonic booms and change the way wings, flaps, and other control surfaces behave in an airplane. The X-1 started acting so wild at Mach 1 because its aerodynamics weren’t designed for supersonic flight.
Lockheed, Bell, McDonell Douglas, and other companies that built early supersonic planes solved the control issues quickly, which made accelerating to Mach speeds pretty uneventful for the pilot. But that left two decades of booming.
Enlarge/ A Bell Aircraft Corporation X-1 supersonic test plane, circa 1950. An X-1 was the first plane to break the sound barrier in Chuck Yeager’s flight on October 14, 1947.
Museum of Flight/CORBIS/Corbis via Getty Images
How loud is the boom?
A supersonic jet boom sounds like a thunder strike hitting nearby—a product of the shockwaves generated mainly by the nose and tail of the aircraft. The boom usually falls between 100 and 110 on a perceived level decibel scale (PLdB), which is used to quantify how people experience sound. A car door slam 100 feet away is 60 PLdB; distant thunder, like the one the ground crew heard during Yeager’s first supersonic flight, is around 70 PLdB. A supersonic boom is on par with a nearby thunder strike, which falls at around 105–110 PLdB.
It’s really freaking loud. And you can easily make it even louder.
This 110 PLdB is estimated for an airplane in a steady, level flight at high altitude. These conditions create what’s known as a “carpet boom” that tracks the aircraft on the ground for the entire time it flies supersonic.
Transitions from subsonic to supersonic speeds and vice versa result in so-called “focus booms,” which can be up to three to four times louder than a carpet boom. This likely gave rise to the popular misconception that the boom is heard only when a plane breaks the sound barrier.
Focus booms are also caused by maneuvers like pitch and dive, where an aircraft gains altitude, levels, and flies back down; turns made with aggressive banking angles work as well. Unlike carpet booms, the booms made by transitions and maneuvers are singular events. The military even tested whether those amplified booms could be projected at chosen spots on the ground to weaponize them. As it turned out, you could do targeted booms, but they proved more scary than lethal.
But despite all the problems with booming, the allure of superior speed was irresistible. Supersonic airplanes could cut the time of transatlantic flights by half. So back in the mid-1950s, when the FAA’s Mach 1 speed limit was still many years away, British and French engineers got to the drawing board and conceived one of the most breathtaking airliners to ever pierce the sky: Concorde.
Enlarge/ A Falcon 9 rocket lifts off Thursday from Cape Canaveral, Florida.
Upgrades at SpaceX’s most-used launch pad in Florida got a trial run Thursday with the liftoff of a Falcon 9 rocket with a Dragon cargo ship heading for the International Space Station.
SpaceX’s Cargo Dragon spacecraft launched at 4: 55 pm EDT (20: 55 UTC) Thursday from Space Launch Complex 40 (SLC-40) at Cape Canaveral Space Force Station in Florida. This mission, known as CRS-30, is SpaceX’s 30th resupply mission to the space station since 2012.
The automated Dragon supply ship took off on top of a Falcon 9 rocket, heading for a monthlong stay at the International Space Station, where it will deliver more than 6,000 pounds of hardware, fresh food, and experiments for the lab’s seven-person crew.
In the last few months, SpaceX has outfitted the launch pad with the equipment necessary to support launches of human spaceflight missions on the Crew Dragon spacecraft. The Cargo Dragon capsule is the same size and shape as SpaceX’s Crew Dragon, but it’s filled with cargo racks and storage platforms rather than seats and cockpit displays.
This week, SpaceX technicians used the newly installed launch tower and crew access arm at SLC-40 to load time-sensitive experiments and supplies into the Cargo Dragon capsule atop the Falcon 9 rocket.
“CRS-30 will be our first Dragon to launch from Pad 40 since we put that brand-new crew tower in place,” said Sarah Walker, SpaceX’s director of Dragon mission management, in a prelaunch press conference.
Building new capability
Starting last year, construction crews at Cape Canaveral erected segments of a more than 200-foot-tall metal lattice tower at SLC-40, right next to the starting blocks for SpaceX’s Falcon 9 rocket. Before then, SLC-40 was based on a “clean pad” architecture, without any structures to service or access Falcon 9 rockets while they were vertical on the pad.
In November, contractors raised the crew access arm to an attach point near the top of the tower. This walkway will allow astronauts to crawl into the Crew Dragon spacecraft during a launch countdown. It also provides access to the hatch on the Cargo Dragon spacecraft for final cargo loading.
Earlier this year, SpaceX tested an escape chute at SLC-40 that would be used in an emergency to help astronauts and ground crews quickly get away from the pad. The chute is similar in function to slide-wire baskets in use for decades at LC-39A, but instead of riding a basket from the top of the tower, personnel escaping a pad emergency would slide down a chute to carry them several hundred feet from the rocket.
SpaceX employees tested the pad escape chute last month at SLC-40. Gwynne Shotwell, SpaceX’s president and chief operating officer, took the ride down the chute. “Astronaut and personnel safety is SpaceX’s highest priority, which is why I had to personally test the new slide,” she posted on X, alongside a wink emoji.
“The team took commercially available off the shelf technology and applied it to the crew tower,” Kiko Dontchev, SpaceX’s vice president of launch, wrote on X. “You are trained on it the same way you are trained on using an emergency exit door on airplane. Only takes a couple of quick physical actions to deploy the slide and anyone can effectively do it.”
As more people travel to space, particularly on larger vehicles like SpaceX’s Starship, simplifying safety systems will be important.
“This system will help us scale to bigger towers and spaceships (think 100 people on Starship),” Dontchev wrote.
SpaceX and its contractors completed all of this work as Falcon 9s fired off SLC-40 every few days with Starlink satellites and other missions.
For the last four years, all of SpaceX’s crew and cargo launches to the space station have departed from Launch Complex 39A (LC-39A) at NASA’s Kennedy Space Center, a few miles up the coast from SLC-40. In 2018 and 2019, SpaceX outfitted LC-39A for Cargo Dragon and Crew Dragon missions ahead of the company’s first human spaceflight mission in 2020.
Walker said the new infrastructure added at SLC-40 is “nearly functionally identical” to the equipment for crew missions at LC-39A. The primary differences are the means of pad escape—the chute instead of slide-wire baskets—and a more robust elevator in the tower at SLC-40.
Previously, SpaceX used both SLC-40 and LC-39A for launches of its now-retired first-generation Dragon cargo capsules, which had their final supplies loaded before SpaceX raised the rocket vertical for launch. Like regular satellite launches on Falcon 9s, both pads could support the first-generation Dragon cargo missions.
“Thanks to this new state-of-the-art crew tower required for our human spaceflight missions, that late-load cargo operation got a massive upgrade, too,” Walker said. “It is much easier to load a huge complement of time-critical NASA science into our Dragon spacecraft in the flight orientation.”
SpaceX has drastically ramped up its launch cadence since building LC-39A for Dragon missions. The company plans nearly 150 Falcon 9 or Falcon Heavy launches this year. When you’re flying rockets every two or three days, it’s inevitable two missions will end up vying for the same launch slots. Most recently, that happened in February, when a NASA crew mission was ready to launch from LC-39A around the same time as a narrow launch window for Intuitive Machines’ first commercial lunar lander. Both had to go off of LC-39A.
“Historically, Pad 40 has kind of become our high rate pad,” Walker said. “We’ve gotten the time between launches down to just a couple of days.”
LC-39A has seen less use, primarily for Dragon crew and cargo flights, Falcon Heavy missions, and other “uniquely complex” missions like the Intuitive Machines lander, Walker said.
Enlarge/ Artist’s illustration of the OSAM-1 spacecraft (bottom) linking up with the Landsat 7 satellite (top) in orbit.
NASA
NASA has canceled an over-budget, behind-schedule mission to demonstrate robotic satellite servicing technology in orbit, pulling the plug on a project that has cost $1.5 billion and probably would have cost nearly $1 billion more to get to the launch pad.
The On-orbit Servicing, Assembly, and Manufacturing 1 mission, known as OSAM-1, would have grappled an aging Landsat satellite in orbit and attempted to refuel it, while also demonstrating how a robotic arm could construct an antenna in space. The spacecraft for the OSAM-1 mission is partially built, but NASA announced Friday that officials decided to cancel the project “following an in-depth, independent project review.”
The space agency cited “continued technical, cost, and schedule challenges” for the decision to cancel OSAM-1.
Mission creep
The mission’s cost has ballooned since NASA officially kicked off the project in 2016. The mission’s original scope called for just the refueling demonstration, but in 2020, officials tacked on the in-orbit assembly objective. This involved adding a complex piece of equipment called the Space Infrastructure Dexterous Robot (SPIDER), essentially a 16-foot-long (5-meter) robotic arm to assemble seven structural elements into a single Ka-band communications antenna.
The addition of SPIDER meant the mission would launch with three robotic arms, including two appendages needed to grab onto the Landsat 7 satellite in orbit for the refueling demonstration. With this change in scope, the name of the mission changed from Restore-L to OSAM-1.
A report by NASA’s inspector general last year outlined the mission’s delays and cost overruns. Since 2016, the space agency has requested $808 million from Congress for Restore-L and OSAM-1. Lawmakers responded by giving NASA nearly $1.5 billion to fund the development of the mission, nearly double what NASA said it wanted.
Restore-L, and then OSAM-1, has always enjoyed support from Congress. The mission was managed by NASA’s Goddard Space Flight Center in Maryland. Former Sen. Barbara Mikulski (D-Maryland) was a key backer of NASA missions run out of Goddard, including the James Webb Space Telescope. She was the top Democrat on the Senate Appropriations Committee when Congress started funding Restore-L in late 2015.
At one time, NASA projected the Restore-L mission would cost between $626 million and $753 million and could be ready for launch in the second half of 2020. That didn’t happen, and the mission continued facing delays and cost increases. The most recent public schedule for OSAM-1 showed a launch date in 2026.
In 2020, after reshaping the Restore-L mission to become OSAM-1, NASA formally laid out a budget for the renamed mission. At the time, NASA said it would cost $1.78 billion to design, build, launch, and operate. An independent review board NASA established last year to examine the OSAM-1 mission estimated the total project could cost as much as $2.35 billion, according to Jimi Russell, a NASA spokesperson.
The realities of the satellite servicing market have also changed since 2016. There are several companies working on commercial satellite servicing technologies, and the satellite industry has shifted away from refueling unprepared spacecraft, as OSAM-1 would have demonstrated with the Landsat 7 Earth-imaging satellite.
Instead, companies are focusing more on extending satellite life in other ways. Northrop Grumman has developed the Mission Extension Vehicle, which can latch onto a satellite and provide maneuvering capability without cutting into the customer spacecraft to refuel it. Other companies are looking at satellites that are designed, from the start, with refueling ports. The US military has a desire to place fuel depots and tankers in orbit to regularly service its satellites, giving them the ability to continually maneuver and burn propellant without worrying about running out of fuel.
Enlarge/ A SpaceX Falcon 9 rocket lifts off with the Crew-8 mission, sending three NASA astronauts and one Russian cosmonaut on a six-month expedition on the International Space Station.
SpaceX’s oldest Crew Dragon spacecraft launched Sunday night on its fifth mission to the International Space Station, and engineers are crunching data to see if the fleet of Dragons can safely fly as many as 15 times.
It has been five years since SpaceX launched the first Crew Dragon spacecraft on an unpiloted test flight to the space station and nearly four years since SpaceX’s first astronaut mission took off in May 2020. Since then, SpaceX has put its clan of Dragons to use ferrying astronauts and cargo to and from low-Earth orbit.
Now, it’s already time to talk about extending the life of the Dragon spaceships. SpaceX and NASA, which shared the cost of developing the Crew Dragon, initially certified each capsule for five flights. Crew Dragon Endeavour, the first in the Dragon fleet to carry astronauts, is now flying for the fifth time.
This ship has spent 466 days in orbit, longer than any spacecraft designed to transport people to and from Earth. It will add roughly 180 days to its flight log with this mission.
Crew Dragon Endeavour lifted off from Florida aboard a Falcon 9 rocket at 10: 53 pm EST Sunday (03: 53 UTC Monday), following a three-day delay due to poor weather conditions across the Atlantic Ocean, where the capsule would ditch into the sea in the event of a rocket failure during the climb into orbit.
Commander Matthew Dominick, pilot Michael Barratt, mission specialist Jeanette Epps, and Russian cosmonaut Alexander Grebenkin put on their SpaceX pressure suits and strapped into their seats inside Crew Dragon Endeavour Sunday evening at NASA’s Kennedy Space Center. SpaceX loaded liquid propellants into the rocket, while ground teams spent the final hour of the countdown evaluating a small crack discovered on Dragon’s side hatch seal. Managers ultimately cleared the spacecraft for launch after considering whether the crack could pose a safety threat during reentry at the end of the mission.
“We are confident that we understand the issue and can still fly the whole mission safely,” a member of SpaceX’s mission control team told the crew inside Dragon.
This mission, known as Crew-8, launched on a brand-new Falcon 9 booster, which returned to landing a few minutes after liftoff at Cape Canaveral Space Force Station. The Falcon 9’s upper stage released the Dragon spacecraft into orbit about 12 minutes after liftoff. The four-person crew will dock at the space station around 3 am EST (0800 UTC) Tuesday.
Crew-8 will replace the four-person Crew-7 team that has been at the space station since last August. Crew-7 will return to Earth in about one week on SpaceX’s Crew Dragon Endurance spacecraft, which is flying in space for the third time.
The Crew-8 mission came home for a reentry and splashdown off the coast of Florida in late August of this year, wrapping up Crew Dragon Endeavour’s fifth trip to space. This is the current life limit for a Crew Dragon spacecraft, but don’t count out Endeavour just yet.
Fleet management
“Right now, we’re certified for five flights on Dragon, and we’re looking at extending that life out,” said Steve Stich, NASA’s commercial crew program manager. “I think the goal would be for SpaceX to say 15 flights of Dragon. We may not get there in every single system.”
One by one, engineers at SpaceX and NASA are looking at Dragon’s structural skeleton, composite shells, rocket engines, valves, and other components to see how much life is left in them. Some parts of the spacecraft slowly fatigue from the stresses of each launch, reentry, and splashdown, along with the extreme temperature swings the capsule sees thousands of times in orbit. Each Draco thruster on the spacecraft is certified for a certain number of firings.
Some components are already approved for 15 flights, Stich said in a recent press conference. “Some, we’re still in the middle of working on,” he said. “Some of those components have to go through some re-qualification to make sure that they can make it out to 15 flights.”
Re-qualifying a component on a spacecraft typically involves putting hardware through extensive testing on the ground. Because SpaceX reuses hardware, engineers can remove a part from a flown Dragon spacecraft and put it through qualification testing. NASA will get the final say in certifying the Dragon spacecraft for additional flights because the agency is SpaceX’s primary customer for crew missions.
The Dragon fleet is flying more often than SpaceX or NASA originally anticipated. The main reason for this is that Boeing, NASA’s other commercial crew contractor, is running about four years behind SpaceX in getting to its first astronaut launch on the Starliner spacecraft.
When NASA selected SpaceX and Boeing for multibillion-dollar commercial crew contracts in 2014, the agency envisioned alternating between Crew Dragon and Starliner flights every six months to rotate four-person crews at the International Space Station. With Boeing’s delays, SpaceX has picked up the slack.
Enlarge/ An annotated image showing the various parts and instruments of NASA’s Voyager spacecraft design.
Voyager 1 is still alive out there, barreling into the cosmos more than 15 billion miles away. However, a computer problem has kept the mission’s loyal support team in Southern California from knowing much more about the status of one of NASA’s longest-lived spacecraft.
The computer glitch cropped up on November 14, and it affected Voyager 1’s ability to send back telemetry data, such as measurements from the spacecraft’s science instruments or basic engineering information about how the probe was doing. So, there’s no insight into key parameters regarding the craft’s propulsion, power, or control systems.
“It would be the biggest miracle if we get it back. We certainly haven’t given up,” said Suzanne Dodd, Voyager project manager at NASA’s Jet Propulsion Laboratory, in an interview with Ars. “There are other things we can try. But this is, by far, the most serious since I’ve been project manager.”
Dodd became the project manager for NASA’s Voyager mission in 2010, overseeing a small cadre of engineers responsible for humanity’s exploration into interstellar space. Voyager 1 is the most distant spacecraft ever, speeding away from the Sun at 38,000 mph (17 kilometers per second).
Voyager 2, which launched 16 days before Voyager 1 in 1977, isn’t quite as far away. It took a more leisurely route through the Solar System, flying past Jupiter, Saturn, Uranus, and Neptune, while Voyager 1 picked up speed during an encounter with Saturn to overtake its sister spacecraft.
For the last couple of decades, NASA has devoted Voyager’s instruments to studying cosmic rays, the magnetic field, and the plasma environment in interstellar space. They’re not taking pictures anymore. Both probes have traveled beyond the heliopause, where the flow of particles emanating from the Sun runs into the interstellar medium.
There are no other operational spacecraft currently exploring interstellar space. NASA’s New Horizons probe, which flew past Pluto in 2015, is on track to reach interstellar space in the 2040s.
State-of-the-art 50 years ago
The latest problem with Voyager 1 lies in the probe’s Flight Data Subsystem (FDS), one of three computers on the spacecraft working alongside a command and control central computer and another device overseeing attitude control and pointing.
The FDS is responsible for collecting science and engineering data from the spacecraft’s network of sensors and then combining the information into a single data package in binary code—a series of ones and zeros. A separate component called the Telemetry Modulation Unit actually sends the data package back to Earth through Voyager’s 12-foot (3.7-meter) dish antenna.
In November, the data packages transmitted by Voyager 1 manifested a repeating pattern of ones and zeros as if it were stuck, according to NASA. Dodd said engineers at JPL have spent the better part of three months trying to diagnose the cause of the problem. She said the engineering team is “99.9 percent sure” the problem originated in the FDS, which appears to be having trouble “frame syncing” data.
Enlarge/ A scanned 1970s-era photo of the Flight Data Subsystem computer aboard NASA’s Voyager spacecraft.
So far, the ground team believes the most likely explanation for the problem is a bit of corrupted memory in the FDS. However, because of the computer hangup, engineers lack detailed data from Voyager 1 that might lead them to the root of the issue. “It’s likely somewhere in the FDS memory,” Dodd said. “A bit got flipped or corrupted. But without the telemetry, we can’t see where that FDS memory corruption is.”
When it was developed five decades ago, Voyager’s Flight Data Subsystem was an innovation in computing. It was the first computer on a spacecraft to make use of volatile memory. Each Voyager spacecraft launched with two FDS computers, but Voyager 1’s backup FDS failed in 1981, according to Dodd.
The only signal Voyager 1’s Earthbound engineers have received since November is a carrier tone, which basically tells the team the spacecraft is still alive. There’s no indication of any other major problems. Changes in the carrier signal’s modulation indicate Voyager 1 is receiving commands uplinked from Earth.
“Unfortunately, we haven’t cracked the nut yet, or solved the problem, or gotten any telemetry back,” Dodd said.
