Why Spaceships Need a Foot Bath

Pictured above is a photo from April 12, 1981, as the Space Shuttle Columbia made its maiden flight into orbit above the Earth. Like most all other rocket launches, including the one out of French Guiana just a few hours ago, the launch requires a huge amount of energy, shown by the fiery columns shooting out of the back of the rockets. And where there’s fire, there’s often smoke. And there appears to be a lot of smoke coming from the launch platform — there are huge clouds shooting off to either side.

But appearances can be deceiving. That’s not smoke — it’s steam. And it’s not waste caused by the rockets — rather, it’s there to help.

Sending a vehicle into space is hard. (It is, after all, literally rocket science.) You need to take something very heavy and get it going very quickly, and that causes all sorts of weird problems. For example, putting a shuttle into space is very loud. As the Dallas Observer notes, “there’s a reason why everyone watches these from several miles away; the noise levels at the perimeter of the launch pad can reach 160 decibels. Even at the three-mile mark, the level is 120 dB.” To give some context for those numbers, according to the CDC, hearing loss can set in after about two minutes of exposure to sounds at 110 dB, sounds at 120 to 150 dB can result in pain and ear injury, and 160 dB is so high that they don’t bother listing it, as there are few things that are that loud. Suffice it to say that you don’t want to be anywhere near a rocket launch unless you have some way to protect your ears.

And in a similar sense, that’s true for things that aren’t ears. The vibrations from these sound waves can wreak havoc even if you can’t hear them, so anything close by has to account for the acoustic shock. And the shuttle itself? By definition, it’s close to the launch pad. As Interesting Engineering explains, “the engines create vibrations so violent, they threaten to compromise the structural integrity of the rockets.” The spacecraft itself needs to be able to withstand this or the mission will literally fall apart. 

The solution? A lot of water. A lot of water. As the rocket engines fire, the launch crew releases nearly 300,000 gallons (about 1.1 million liters) of water onto the launch platform in under a minute — the equivalent of about 200 fire engines pumping out water at full capacity. (Here’s a video of a test release.) That water helps dampen the sound, typically reducing it significantly under the 145 dB level that the spacecraft can handle. In a sense, the spaceship gets a big foot bath instead of wearing earplugs.

The visual result of all this is what you see above. The heat coming off the rockets hits that flood of water, almost instantly vaporizing a lot of it. Huge steam clouds — not smoke —¬†emanate from the launch platform, billowing in multiple directions.

 

Bonus fact: In the image above, we get a pretty clear view of the spaceship and its rockets — despite the fact that there’s a lot of steam and, presumptively, a lot of exhaust coming out of the rockets, too. That’s by design — less so for photographic reasons and more for the safety of the spaceship. As seen in this video, the launch pad has huge trenches that direct the steam and rocket exhaust away from the spacecraft. The exhaust can reach 2200 degrees Fahrenheit (1204 degrees Celsius), so getting it away from all of the technology on the platform itself is incredibly important., 

From the Archives: As the World Turns: The science-y reason why the U.S. uses Florida as a launch site.