OPINION: In spaceflight testing, what defines a failure?
Starship SN9 explodes as it impacts the landing zone in off nominal conditions. This often brings up the question of what defines a failure in spaceflight testing. Image: Nicholas D’Alessandro, Spaceflight Insider
In recent months, several companies have made great strides in the realm of testing advanced spacecraft, despite public perception some would label a failure. It’s this perception that brings up the question: “In Spaceflight testing, what defines a failure?”
In February, SpaceX conducted the second high-altitude test flight of its Starship spacecraft from its building and launch site in Boca Chica, Texas. The flight profile of the Serial Number 9 test article, commonly referred to as SN9, called for a launch and climb to about 10 kilometers.
Something appeared to be ejected from Starship SN9 moments after two Raptors began to ignite for its landing flip and burn. Credit: Nicholas D’Alessandro, Spaceflight Insider
On its way to altitude, each of the three SN9 Raptor engines shut down one at a time. The last engine cut off at apogee, allowing Starship’s aerodynamic surfaces to take over, and guide the spacecraft on its belly back to the launch site, where it would then be flipped to the horizontal by two of its three Raptor engines.
If all went according to plan, Starship would land as many Falcon 9 boosters do; standing straight up.
Before the first flight of Starship (the SN8 test article) in December 2020, the company CEO Elon Musk only gave a one-in-three chance of the vehicle completing every test objective that had been laid out for the experimental spacecraft.
Incredibly, Starship SN8 and SN9 performed nearly flawlessly save for a harder-than-expected landings resulting in the destruction of both test vehicles. In the case of SN8, low pressure in the vehicle’s header tank caused one engine to be starved of propellent. However, during SN9’s landing attempt, there appeared to be an issue with a Raptor engine itself.
Even though the tests were considered by the company to be an astoundingly successful victory, many in the public and media perception viewed Starship’s voyage as a failure.
Virgin Galactic Flight test crew walk to the VMS Unity and VMS Eve prior to the aborted test flight. Credit: Virgin Galactic
In December, Virgin Galactic attempted to conducted a full powered flight test of its Virgin Spaceship Unity from Spaceport America in New Mexico. However, the onboard computers monitoring the engine parameters aboard Unity lost connection, and the suborbital space plane’s main engine did not fully ignite.
The pilots were able to glide the spacecraft safely back to the runway. The data gathered on this flight, however, was invaluable even though the test flight did not proceed completely as planned.
While some of the specific test objectives Virgin Galactic set in place for its flight were not met, it’s still very difficult to classify the test flight as a “failure.”
From an engineering perspective, the main objective of testing and test flights is to gather data. Even though Unity’s flight did not proceed as intended, the company was able to gather multiple data points that will not only help to improve the efficiency of the spacecraft’s onboard computer system, but will also ensure the safety of future flights that will eventually fly paying customers to suborbital space.
It’s very easy to think of a test flight ending in an explosion, or a spacecraft cutting its flight short, as a failure. The perception in today’s society carries the expectation that every flight from space companies with high success rates must end perfectly, regardless of how strenuous the test objectives may be.
The destruction of the space shuttle Challenger 73 seconds after liftoff. Credit: NASA
As mentioned before, the main purpose of test-flying hardware is to gather data that will help to improve the safety and efficiency of spacecraft for operational flights. Even though SpaceX’s flights ended in flames, the amount of data gathered beforehand is worth its weight in gold by helping to improve the systems onboard Starship.
In the space world, there is no such thing as too much testing, as a vehicle can never be made “too safe.” Gathering design and procedures improvement data from spaceflight testing is greatly preferred over learning lessons the hard way.
On the morning of Jan. 28, 1986, space shuttle Challenger was destroyed 73 seconds after liftoff, killing all seven astronauts onboard.
After the accident, a team was established to collect and piece together data collected from Challenger’s short flight, to not only discover the point of failure, but to prevent the disaster from happening again.
The space shuttle was an incredibly unique machine from a spaceflight testing perspective, in that all of its components were flown for the first time with a crew onboard. There was never an uncrewed test flight of the system, like its prior space-going predecessors.
This simply meant that NASA and contractor engineers were learning and gathering data with each flight. It only took four flights of the space shuttle for the agency to declare it as “operational.” But those close to the program knew that it was anything but.
SpaceX’s first stage boosters land successfully so often that it becomes news when one isn’t successful. The Arabsat-6A mission in April 2019 saw all three FH first stage core boosters land safely. Pictured here are the two side boosters while the center core landed on a drone ship at sea. However, it fell over during transport back to shore. Photo Credit: Scott Schilke / SpaceFlight Insider
Each shuttle flight brought about new challenges and anomalies that would have to be studied and added to a list of events known as “in family” occurrences. This means that problems that arose during any given flight that were not deemed unsafe from a crew perspective, were grouped together and labeled as problems that would not compromise a mission.
While an eventual probable cause for the Challenger disaster was identified, and design improvements to the shuttle’s solid rocket boosters were eventually implemented, no amount of design and safety upgrades would bring back the seven lives lost that day.
In a world championed by continuous success in the spaceflight industry, mainstream media outlets may find that the continual accomplishments and nominal missions do not grab the attention of the consuming public as well as an explosive rocket failure would.
With this thought process, and with an increase in experimental test flying, more scrutiny is put on these companies if a test does not appear to go 100% according to plan.
As was the case with the space shuttle, commercial space companies like SpaceX have become victims of their own success in the eyes of the public and the media.
The Challenger tragedy is just one of many examples why spaceflight testing is so important before a vehicle is considered operational.
With the flight tests of both Starship and Virgin Galactic’s Unity spacecraft, both companies will be able to gather data, implement more-efficient design and procedural changes and help to ensure that space travel will be as safe as possible for everyone involved.
Video courtesy of SpaceX
Cullen Desforges
Having a life-long interest in crewed space flight, Desforges’ passion materialized on a family vacation in 1999 when he was able see the launch of Space Shuttle Discovery on STS-96. Since then, Desforges has been an enthusiast of space exploration efforts. He lived in Orlando, Florida for a year, during which time he had the opportunity to witness the flights of the historic CRS-4 and EFT-1 missions in person at Cape Canaveral. He earned his Private Pilot Certificate in 2017, holds a degree in Aviation Management, and currently works as an Operations Analyst in the aviation industry in Georgia.
