Next year when SpaceX’s Dragon capsule is hurtling toward the Pacific Ocean at 540 miles per hour on its return from the International Space Station, the technology ensuring the astronauts inside land safely is a component it seems we’d have mastered by now: the parachute.
Compared to the complex technology packed into a modern spacecraft, you would think the simple parachute would be the easiest part of the design but in fact it’s one of the biggest challenges.
“Parachutes, they look easy but they are definitely not easy,” Elon Musk said in October at a press conference at SpaceX, “We’ve had so many engineers quit over the parachutes.”
During a drop test in April, SpaceX’s Dragon capsule crash landed in the Nevada desert because three main parachutes didn’t inflate.
In November, only two out of three parachutes deployed on Boeing’s Starliner capsule during an abort test.
Not surprisingly, in November when the Office of Inspector General, the agency responsible for oversight, released its report on the state of NASA's Commercial Crew Program it called out issues with parachutes as a major hurdle toward NASA’s goal of launching American astronauts again from American soil.
“Boeing and SpaceX each face significant technical challenges with parachutes, propulsion, and launch abort systems that need to be resolved prior to receiving NASA authorization to transport crew to and from the ISS.”
What makes parachutes so hard to get right? After all, they've been in use since the Mercury program to slow the spacecraft during an aborted launch or in its final descent to Earth.
“They seem simple in their design but the sequencing of the parachute, the inflation, their ability to counteract the load from the spacecraft coming in from orbit and the interaction with all of the aerodynamic conditions of the day gets to be very complex," said John Mulholland, Vice President and program manager for commercial crew at Boeing.
And just as engineers are trying to push against limitations in other space technology, parachutes are no different: the demand for lighter and cheaper is ever present.
“It costs a lot of money to take something to space so if you can give a program manager or chief engineer 10 pounds back, you’re a hero,” said Ricardo “Koki” Machin, Chief Engineer for NASA's Orion Crew Module Parachute Assembly System.
It’s pretty simple: the lighter the load, the cheaper the flight because less fuel is required. And for commercial companies like SpaceX and Boeing that hope to make additional income by selling empty seats on their capsules to tourists for $50 million to $90 million a pop, every ounce counts.
So engineers are testing how light they can make parachutes that are still capable of doing the job. Apollo parachutes were made entirely of nylon. Today’s parachutes are a combination of nylon and Kevlar making them much lighter.
“When you try and make it really light, it’s inevitable that you’re going to find the cliff somewhere. And I think that’s part of why we see failures today that we haven’t seen in the past,” Machin said.
SpaceX has been at the forefront of pushing to make their parachutes as light as possible. For comparison, the Orion parachutes are twice as heavy as the SpaceX parachutes even though they are about the same size. SpaceX has experimented with making the canopy out of new lighter, stronger materials such as Technora and Zylon.
“Those materials have to be treated a certain way, you gotta keep them out of UV light so they hadn’t traditionally been used,” explained Kurt Hempe, Director of Space and Inflatables at Airborne Systems the company that manufactures the parachutes for NASA, SpaceX, Boeing and Blue Origin.
Early testing resulted in parachutes ripping and blowing apart, panels blowing out and suspension lines breaking.
The weight of the parachutes isn’t the only problem.
In the parachute world, engineers try to predict the load the parachute experiences during inflation.
"And there's where it becomes kind of tricky because none of our models are that level of detail so we make assumptions, Machin said.
It turns out NASA, SpaceX and Boeing have all been using faulty load assumptions from Apollo parachute data to design their modern parachutes.
“I look at what Apollo published and what they did and I now recognize they probably weren’t carrying as much safety factors as they thought they were," Machin said.
So parachute engineers today are dealing with a triple whammy of issues: Trying to make lighter parachutes based on Apollo load assumptions that probably weren't operating within safe margins.
“NASA had, since the Apollo program, a way of determining the loads in the risers on the parachutes,” SpaceX COO Gywnne Shotwell said in a December meeting with journalists as reported by SpaceFlight Now. “They made a (conservative) assumption … from the Apollo program. We did it. Boeing did it. We were just following their standard."
This causes a problem called asymmetrical load distribution in which the parachute doesn't inflate evenly and therefore isn't effective.
“As you drive that parachute lighter and lighter, your safety margins become less and less and during the testing with SpaceX we found out that the asymmetry factor is in fact an issue,” Hempe said.
The parachute industry had a collective aha moment and got to work making major changes.
After SpaceX’s catastrophic parachute failure in April with its Mark 2 parachute, it overhauled the design and went back to testing. The new parachute is called the Mark 3 and the system includes enhancing the parachute suspension lines known as risers to handle the massive loads during launch abort and descent.
Several successful tests later and Elon Musk feels like they have finally nailed it.
“The Mark 3 parachutes in my opinion are the best parachutes ever. If you were to compare the margin of safety factor to let’s say Apollo, this is twice the safety factor of Apollo. This is really a good design.” Elon Musk said at press conference from with NASA administrator at SpaceX in Hawthorne in October.
SpaceX has conducted seven successful drop tests of the Mark 3 parachutes and has stated it wants to achieve at least 10 before they fly humans to the International Space Station which it hopes to do next year.
Boeing took a different approach. Because Boeing’s Starliner is basically a scaled down Orion, it just made sense to model their parachutes off Orion. The systems are so similar that Boeing relied on the Orion testing to inform their program.
“We only did two development tests because the 40 plus tests that they did for Orion, we count as part of our development campaign," said Boeing spokesman Josh Barrett.
But Boeing’s latest test revealed a safety issue no computer model can prevent.
In early November, Boeing tested the Starliner’s ability to quickly abort at launch commonly known as a ‘pad abort test.’ The capsule performed perfectly rocketing off the launch pad at 650 mph but when it descended only two of the three main parachutes deployed.
The cause turned out not to be a problem with the parachute itself but with the rigging process. There wasn't a secure connection between the pilot chute that pulls out the main chute. To put it simply, a pin was missing. The technician packing the parachute couldn’t visually verify the pin was missing because it was covered by a protective sheath.
Boeing has implanted new process check-outs to ensure a secure connection and will be completing three more drop tests in the coming months.
Hempe says that the failure had a silver lining proving Boeing’s safety margins.
“The parachutes worked perfectly and obviously have more (safety) margin than we anticipated because the two that did deploy survived even with the added weight of the service module,” Hempe explained. The service module which carries cargo would detach during descent from space but would still be attached during an abort at launch.
Boeing declared the test a success stating that the deployment of only two parachutes is acceptable within the test parameters for their landing sequence.
But it raised the question: what if that happened when humans were inside?
It actually has happened. On August 7, 1971 when astronauts David Scott, James Irwin and Al Worden were returning to Earth in the Apollo 15 crew module, they heard what nobody wants to hear: “Stand by for a hard impact.” Unbeknownst to them, one of the three parachutes on their capsule didn’t inflate. They splashed down violently into the Pacific Ocean but nobody was injured.
It remains a dramatic close call that reinforces the parachute's singular goal: to keep the astronauts alive.
“If the parachutes don’t work we lose our crew. It’s of the utmost importance.” Hempe said.
On December 20th, Boeing’s Starliner will launch from Kennedy Space Center and travel to the International Space Station for its first ever orbital test flight. The uncrewed capsule will carry supplies to the ISS. Eight days later it will return to Earth, descending at 28 feet per second buoyed by its parachutes, and land in the New Mexico desert.
This is the last critical test of the capsule before it flies humans in 2020 and all eyes will be on those big red, white and blue parachutes.
If everything goes well, we'll see all three.
Contact Rachael Joy at 321-242-3577 or email rjoy@floridatoday.com. Follow her on Twitter @Rachael_Joy.
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