The International Space Station will soon be equipped with its very own same-day delivery service, for returning critical scientific samples back to Earth. The service will be provided by the Terrestrial Return Vehicle (TRV), a small, wingless capsule that can be loaded up with samples and ejected from the airlock, guaranteeing delivery back to Earth in under 24 hours. A number of these TRVs will be shipped up to the ISS as part of a normal cargo run (via the SpaceX Dragon capsule, perhaps), and then the astronauts aboard the space station will be able to send samples back down to Earth whenever they want — a bit like a gravity-powered courier service (and coincidentally, probably the most reliable courier service in the world).

As you probably know, getting to the International Space Station is a rather arduous and expensive task: Generally, it involves loading up a fairly big capsule with a few tons of cargo, and then burning millions of gallons of fuel (and hundreds of millions of dollars) to lift it a few hundred miles into space. Technically it should be a lot easier to get stuff back to Earth from the ISS — you can always trust gravity to take care of everything — but for some reason, the ISS’s only return capability is provided by the very same cargo capsules. In other words, to send something back from the ISS, we first have to spend a few hundred million dollars getting a return vehicle up there.

The Terrestrial Return Vehicle, made by Intuitive Machines, will change all that. The TRV is a small, wingless capsule that looks a lot like the Space Shuttle or Boeing X-37B space plane, but without the stubby little wings. There’s no word on the TRV’s actual dimensions, but I think it’s probably no more than a meter long. The concept art suggests it’s about the size of a small child. (But no, amusingly enough, the first version of the TRV won’t be able to carry living things.) The TRV will be loaded up with scientific samples, pushed into an airlock, and then shunted out into space by the Space Station’s Japanese-made robot arm. It will then return to Earth much like any other spacecraft, descending through the atmosphere, eventually deploying a drogue parachute to slow it down from supersonic speeds, and then a larger parachute to bring it safely down to a landing site in Utah.

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The return to Earth will take about six hours. Because the ISS orbits the Earth about 15 times per day, the total delivery time should always be under 24 hours. This is significant because the International Space Station is home to many scientific experiments — and the samples produced by those experiments would much prefer it if they could be sent straight back to Earth, rather than waiting weeks for the next cargo ship. As Popular Science points out, the ISS is actually a very important location for research because of its zero-gravity environment — some things, like bioprinting organs or developing new pharmaceuticals, are much more effective when cells can freely grow in three dimensions, rather than on Earth where gravity crushes everything.

Intuitive Machines’ TRVs are being developed in coordination with NASA and CASIS — the non-profit Center for the Advancement of Science in Space, which was recently endowed with the responsibility of making sure that we make good use of the US laboratory aboard the ISS. The first batch of TRVs is scheduled to be sent up to the ISS in 2016. At first, the TRVs will just be used to return scientific samples — but apparently they’re working on a version that’s capable of returning live rodents, too.

(NASA is currently preparing to send mice up to the ISS, but the current plan is to butcher them up there, and send their frozen organs back to Earth — couriering live rodents in a TRV would be a little more humane, I guess.)

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