Engineers say FOD is a four-letter word, but there’s nothing funny about foreign object debris and its potential to trigger a disaster.
The incident happened on October 5 at around 10:25 a.m. ET, while a SpaceX pad crew was preparing Crew Dragon Endurance for a Falcon 9 rocket apex launch. With the four Crew-5 astronauts already inside the capsule and the hatch closed, a keen eye spotted a single human hair in the latch seal. The hair was designated FOD – an engineering term for foreign object debris – causing the pad crew to take action.
The countdown had just passed T-90 minutes, so time was of the essence. The pad crew calmly reopened Endurance‘s hatch and removed the offending strand. They performed another inspection, thoroughly cleaned the gasket area again, and closed the hatch for the second and final time. A subsequent pressure check confirmed a tight seal.
The whole affair only lasted a few minutes and the launch was unaffected. The Falcon 9 liftoff took place at noon as scheduled, with Crew-5 astronauts—Nicole Aunapu Mann, Josh Cassada, Koichi Wakata and Anna Kikina – successfully reaching the International Space Station the following day.
That the SpaceX pad crew would take the time to remove a single hair before a rocket launch is telling and completely understandable. In the aerospace industry, FOD is defined as any object that does not belong in a specific location, whether that location is a hatch seal, engine, cockpit, or the runway. Debris in the wrong place can damage equipment, facilitate suboptimal system performance, and trigger outright malfunctions.
It’s a problem in many industries, but for the aerospace industry it’s a problem that costs $4 billion every year, according at Boeing. NASA runs a BE program at Kennedy Space Center, the purpose of which is to “minimize the possibility of damage to or loss of flight hardware or injury to personnel due to lost items in flight hardware items, resulting in the preservation of national resources”.
Speaking to me on a video call, Tom Simon, deputy director of spacecraft at NASA’s Johnson Space Center, said: “We’ve all been trained from day one when it comes to systems of flight, to pay attention to FOD.” Foreign objects, such as pencils, paper clips, screwdrivers, hair and dust, “may seem minor”, but they could, among other things, lead to a “gasket slowly leaking overboard”, it said. -he declares. “When we build systems, we take it seriously,” he added.
As an engineer, FOD is “rooted in your system,” John Posey, NASA’s chief engineer for Crew Dragon, told me on the same call. It is “considered a major risk in training programs” because FOD has the potential to “bring down rockets and planes”, he explained.
Simon and Posey weren’t able to talk about specific SpaceX policies and protocols, but they weren’t surprised by the pad crew’s actions in removing human hair. FOD related to surface sealing is a serious concern. When it comes to a sealing surface and when it comes to ensuring a perfect seal, “you don’t want anything leaning against it,” Posey said. “Something like hair, depending on its size and orientation, can lead to a leak.”
Posey said that for urgent situations like the final closure of a capsule hatch, the sudden onset of FOD should be factored into the timing and process, in addition to having a contingency plan should this scenario occur. occur. Pad crews should “back up, remove the item, re-inspect and even clean the seal, and then get on with the job you’re trying to do,” Posey said.
It’s not just the hatches that are subject to the risk of FOD. Launch operators implement processes to mitigate the risk of FOD, such as the use of covers or shields when work such as cutting or sawing must be performed near spacecraft. And of course the operators themselves must be clean. Propulsion systems, in which fuels and oxidizers are pumped through high-pressure systems, can be affected by FODs, said Posey, who worked on the Space Shuttle during its final days and “spent thousands hours on the propulsion systems, working on the ground with technicians, to make sure everything is going well.
As Simon explained, the degree of cleanliness required often depends on the nature of the project or the assignment itself. Posey said each system needs its own control plane, with engineers setting acceptable limits and deciding what needs to be filtered.
Cleanroom protocols for uncrewed satellite launches tend to be minimal, “to the point of washing your hands and putting on gloves,” he said. Missions involving a crew are a different story, however. “With crews, not only does the avionics system have to work, but you also don’t want things flying all over the place,” in addition to keeping the joints clean, Simon said. Once in orbit, microgravity can suddenly float unnoticed FODs, including hair and dust. Posey said filtration systems are designed to deal with that sort of thing, “but you still want to avoid the hassle,” like requiring covers over hatch seals, among other measures. And “even blankets should be cleaned and checked for leaks,” he added.
Posey gave some sage advice: “Always make sure you open a system in a clean room, do only what you need to do, and do an inspection before you shut it down.” And “if you see anything that doesn’t look right, come in and investigate,” because it’s a “necessary burden,” he said. A second pair of eyes won’t hurt, he added. “FOD will find a way into your system,” Posey said, hence the term “Smart FOD.” He recounted an incident in which a slipper, or shoe cover, was suddenly discovered in the shuttle compartment. “It just slipped off someone’s foot, and that stuff can be fun in retrospect,” Posey said, but booties or duct tape or anything else that doesn’t belong can be a flammability issue. .
Measures to prevent FOD from entering complex components or systems begin in the cleanroom, and each cleanroom has its own cleanliness requirements, depending on the project. Cleanrooms “are specially certified and vetted to a certain level of cleanliness based on what’s inside,” and items typically must be approved before they’re allowed in a cleanroom, Posey said.
Lockers are available to store loose items; tape and sticky floor pads can secure items that need to be in the room; and the ties can catch anything that accidentally falls. The suits, known to engineers as “bunny suits”, cover the arms and legs and usually feature a hood with a hair net. Beards are covered with beard nets, while shoes are covered with slippers.
“Once you’re set and ready, you walk through a double door,” Posey said, the first of which “closes behind you, then you walk into the white room.” In the middle chambers of some double doors, “air blows all over you, sucking in dust or debris,” he explained. Staff will collect any FOD found and investigate its origin and if further checks are needed. Cleanrooms “are never clean enough,” Posey added.
These measurements are an additional but necessary headache. The good news is that FOD detection improves over time. Cameras are now commonly used to observe virtually every corner of a launchpad, while X-ray and CT scanners can peer inside objects and create 3D images of a room’s interior. With these tools, engineers can “see assembly issues” and “detect FODs that otherwise wouldn’t have been found,” Posey said. An increased ability to detect FOD is of growing importance to the private sector, especially in the era of component reuse.
The human hair found inside the hatch seal may or may not have caused a problem during the Crew-5 flight, but that doesn’t matter. What matters is safety and the elimination of anything that could endanger human lives. Engineers will continue to research FODs, regardless of the inconvenience they may cause.
After: Remember Company: The test shuttle that never flew in space.
#single #human #hair #stopped #SpaceX #launch