Now that SpaceX has landed a rocket after launching it into space, the possibility of reusing rockets isn’t as fantastic of an idea as it once was. But is it really that much more affordable?
SpaceX has promoted reusability as a major cost-saver for the private spaceflight industry. Right now, rockets are treated as trash once they've taken off, so companies must spend millions of dollars on manufacturing brand new rockets for every single flight. It costs $60 million to make the Falcon 9, and $200,000 to fuel it, according to SpaceX CEO Elon Musk. Reusing rockets could substantially lower these costs, he says; theoretically, a rocket would only need to be refueled to launch multiple times again.
SpaceX needs to be certain that its returned rockets are capable of flying again
That’s not exactly right. SpaceX needs to be certain that its returned rockets are capable of flying again. The Falcon 9 experiences major temperature changes during its flights, as well as intense pressures and vibrations from the winds in the atmosphere. These all produce wear-and-tear on the vehicle's hardware — meaning the rocket might need repairs and updates before it can launch again. Refurbishing a rocket engine is often expensive. And if those repairs take too long, SpaceX can’t launch its vehicles as frequently.
Refurbishment costs were one of the main reasons the Space Shuttle — another partially reusable space system — turned out to be so expensive. The Shuttle launched with the help of a giant expendable fuel tank and two solid rocket boosters that were recovered post-launch. The Shuttle could then land back on Earth once its time in space was over, like a plane after flight.
The reusable design of the Shuttle was meant to save money, since all but the external tank could be used again post-launch. "Unfortunately it didn’t work out that way for the Shuttle," says Wayne Hale, a former manager of NASA's Space Shuttle program, and a member of the NASA Advisory Council. "It was a very complicated vehicle that took an awful lot of refurbishment to get it to fly again." The Shuttle's main engines had to be replaced after every few launches. The vehicle also needed lots of inspections and repairs between missions. Additionally, its solid rocket boosters needed constant updates once they had been recovered from the ocean, and the external tank had to be built anew for each flight. All together, this helped to drive up the cost of each Shuttle mission to somewhere between $450 million and $1.5 billion per launch.
The Falcon 9 is nowhere near as complex as the Shuttle, so it won’t require as much work. But the vehicle does experience some of the same flight conditions as the Shuttle did. The Falcon 9 first stage — the 14-story-high rocket body that SpaceX recovered — can experience temperature fluctuations that range from -250 degrees Fahrenheit in space to upwards of 1,000 degrees Fahrenheit during its trip back through the atmosphere, according to Steve Poulos, a former NASA project manager who worked on the Space Shuttle. "This is where the design part becomes paramount," says Poulos. "SpaceX is probably using metals, and some parts are probably composite, which are able to withstand those temperature constraints and not do any damage."
A lot hinges on the design
The Falcon 9 also experiences heavy pressures and forces from the gases in the atmosphere. The first stage reaches a maximum speed somewhere between Mach 5.5 and 7.5. As it travels through the air, the high-altitude winds can shake and press on the vehicle, causing damage. "Those atmospheric loads can be up to hundreds of pounds," says Poulos
SpaceX does have experience with flying a rocket multiple times, though. Its Grasshopper vehicle, which allowed the company to test out the Falcon 9's reusable landing system, flew a total of eight times. However, Grasshopper only traveled up to a height of 2,440 feet and didn't travel to and from space — so it didn’t experience the more-abusive conditions the Falcon 9 must stand up to.
Really, a lot hinges on the design. If the Falcon 9 isn’t damaged much during launch and descent, repairs may not be expensive or time-consuming. Last year, SpaceX said it was confident that it could land its rockets and re-fly them "with no required refurbishment." Now engineers must find out if that design holds up to reality. If it does, a reusable vehicle makes sense.
That’s why SpaceX is studying the Falcon 9 that landed on Monday — to find out just how damaged it is. Musk says that particular booster won't fly again, but it will give the company insight into how much refurbishment may be needed between flights — if any.
Regardless, Poulos argues refurbishment costs won't come anywhere close to the cost of manufacturing an entirely new rocket. He suspects most of the refurbishment will be dedicated to inspections and making minor adjustments so that the vehicle meets the standards required for spaceflight. Those costs would be about half a million dollars — not the $60 million needed to build a first stage, says Poulos. "It’s still a pretty significant cost reduction."