On Aug. 2, 2020, NASA astronauts Robert Behnken and Douglas Hurley safely returned to Earth in SpaceX’s Crew Dragon Demo-2 after their stint aboard the International Space Station. Their trip marked the first time humans have traveled to orbit on a commercially developed aircraft. We’re definitely living in the future, huh?
There’s another reason Bob and Doug’s return was notable, though. The spacecraft made a water landing (or splashdown) — NASA’s first in 45 years. After Apollo-Soyuz’s splashdown in 1975, NASA switched to ground landings. So, why does SpaceX land on water?
Why does SpaceX land on water?
When it comes to bringing astronauts back from space, there’s only one goal: Get everyone home safely. That can be accomplished either by landing on water or solid ground, but there are two big reasons why a water landing might be preferred.
First of all, landing in water cushions the spacecraft’s landing without the need for a braking rocket. Instead, the capsule is equipped with parachutes that allow it to glide down to the water. SpaceX originally planned for the Crew Dragon to do ground landings, but ultimately decided that doing a splashdown would allow for a more simplified capsule design. SpaceX founder Elon Musk offered some further explanation on Twitter:
All correct. Parachutes were originally the backup landing system, with SuperDraco thrusters as primary. Difficulty of proving thruster landing safety *and* architecture being suboptimal for moon/Mars caused us to change focus to parachutes.— Elon Musk (@elonmusk) August 2, 2020
Secondly, when you consider the fact that most of the planet is covered with water, it’s obviously a lot easier to aim for the water than for the land. There’s certainly less room for error when it comes to aiming a capsule for a water landing. However, water landings aren’t completely without risk.
What are the risks of water landings?
As we already mentioned, NASA stopped doing splashdown landings after the Apollo-Soyuz mission’s water landing in July of 1975. During this reentry, the crew splashed down safely, but there was one serious problem. During reentry, the crew was accidentally exposed to toxic hydrazine and nitrogen tetroxide fumes from unignited rocket propellant. This led to breathing and eye problems for the astronauts aboard, who were hospitalized for two weeks after splashdown.
In the case of astronauts Bob and Doug, engineers aboard recovery ship GO Navigator detected high levels of dinitrogen tetroxide around the capsule. After a 30-minute purge of the remaining fuel in the thruster system, they were able to open the hatch and be loaded onto the recovery ship safely.
There was one other issue with Bob and Doug’s reentry — after the capsule landed in the Gulf of Mexico, several privately-owned boats filled with curious onlookers surrounded it. SpaceX officials chased many of these private citizens off, warning them that they could be exposed to dangerous fumes if they remained in the area. Eventually, though, the lookie-loos made themselves scarce and everything went according to plan.
All things considered, the first water landing in 45 years went pretty darn smoothly. It’s hard not to be excited about the leaps being made within the realm of space travel these days (if only because it gives some people hope that they might be able to escape the planet someday). Welcome back, Bob and Doug!