Right now, discarded parts from old spacecraft, bags of pee, and dead probes are just floating around in space, but does not have to be like that! We've figured out tons of ways to reduce space waste across an entire mission, from before the launch to after each goal has been accomplished. Let us start at the beginning - during spacecraft assembly. At this early stage, we already have opportunities to reuse pieces from previous missions instead of manufacturing them from scratch. Here's how NASA took that opportunity to make the Phoenix Mars Lander. 

Spacecraft take a long time and lots of money to make. Most of them are designed and built from scratch with every single component created just for one mission, but not the Phoenix Mars Lander. This probe was pieced together from several missions that came before it and subsequently rose from their ashes all the way to Mars. Dr Frankenstein made his monster, but if he focused his efforts on space, he might have come up with something more like the Pheonix Lander.

On Mars, the Phoenix Lander collected some pretty cool data and we already have a video all about its search for Martian water, but that search started years before. Phoenix succeeded the cancelled 2001 Mars Surveyor Lander, which never got its day in the Martian sun because its partner, the 1999 Mars Polar Lander, was lost upon arrival on Mars. Since Surveyor was designed to communicate with Earth through the Polar Lander, it pretty much had to be scrapped.

So, Phoenix rose from the ashes to take over Surveyor's science goals, including searching for water. But first, it had to do with the Polar Lander hadn't and safely reach the Martian surface. This was a lander, not a rover.

Its job was to land safely and then, collect all of its data in one spot. To accomplish that goal, it needed to know where space ended and Mars began. That's helpful to, you know, not crash and to get an idea of where it was on its flight in relation to Mars.

The Phoenix Lander used a radar system, but not just any old radar system. The Phoenix radar system was originally designed to be an altimeter for fighter jets. Altimeters tell pilots how high they are in the air. A radar altimeter accomplishes that goal by emitting microwaves and monitoring when they bounce back.

The longer it takes for those microwaves to return, the farther you are from the ground.

In theory, the same principle works perfectly well on Mars, but the system still needed to be adapted for Phoenix to measure altitude and velocity during its descent. One of those adaptations included not getting distracted by the heat shield jettison.

Fighter jets don't have heat shields, so it wasn't originally designed for those conditions. During testing, engineers raised concerns that the sudden jerk as the heat shield disconnected would confuse the system. The Phoenix team had to change the timing of when the radar sent its microwaves to account for the jettison.

That way, it didn't accidentally detect Phoenix yeeting its heat shield during flight as if it were Martian ground. Because it was repurposed, this radar system required more testing than all previous Mars radar systems from NASA combined. So, in the end, it did its job well and Phoenix successfully landed on Mars.

Once it landed, the probe's secondhand science mission could begin. To accomplish its goal of digging into Martian dirt for signs of water, Phoenix needed a robotic arm. But once again, the electric motors on that arm weren't new to the mission. Those motors were bulk ordered for previous missions, Spirit and Opportunity.

So, there was still a bunch left over that had gone unused - and not all of them still worked. Now, the ones that went to space in Spirit and Opportunity surpassed performance expectations in real Mars conditions. The question was whether a few malfunctioning motors in the leftover pile meant there were issues with the rest of them.

So, the Phoenix team took a thorough look at the leftover motors, eventually giving them the thumbs up. They even added extra sensors that would alert them if anything fell apart during transportation from the construction site in Colorado to the launch site in Florida - both in the USA and just like the refurbished radar, Phoenix's arm motors worked like a charm. After all that testing and adapting, the Phoenix Lander touched down on Mars' surface on May 25th, 2008.

It successfully sent back data with evidence for water ice hiding in the soil on Mars with signs of calcium carbonate, a chemical marker indicating the presence of liquid water. Not bad for a probe that brought "Reduce, Reuse, Recycle" to space. In fact, the turn of the millennium saw a good amount of Martian traffic, all created by NASA in an attempt to do planetary science on a budget.

So, that's how a ghost mission in the form of Surveyor, some spare parts from Spirit and Opportunity, and even hardware meant for fighter jets, all flew to Mars together and did some great science too.

So, once it launched, that lander went full steam ahead on new and exciting space science, but some researchers are working to keep the recycling mentality among astronauts - even in the middle of a mission. Soon, we might be able to recycle our mid-mission pee and even, breath into materials that we can use again like 3D-printer plastic.

Here's Reed to explain how.

NASA wants to send humans to Mars, but it's not going to be easy. In addition to months of isolation, heavy doses of dangerous radiation, and the stress of doing basically the most risky thing ever, you're also not gonna have a lot of room. So, what if astronauts could recycle their own waste into something useful? NASA's already working on perfecting 3D printing in space, so if astronauts need a part or a tool, they can just print them instead of having to carry everything they could possibly need.

Now, they're also sponsoring research into recycling human waste like urine and carbon dioxide into things like food and plastic. We were curious about how that would work, so we got in touch with the researchers to learn more about what they do. One of the projects led by biologists at Clemson University in South Carolina is looking to use genetic engineering to turn astronauts' urine and the carbon dioxide waste that they exhale into nutrients like omega-3 and plastic for 3D printing. But in order to do it, they're going to need a little help - first from algae, then from yeast.

The plan is for astronauts to grow algae using energy from the Sun, carbon dioxide, and nitrogen from urea, one of the main components of urine. As it grows, the algae will produce lipids, a type of organic compound that includes fatty acids. Those fatty acids, plus some more nitrogen, is the yeast's favorite dinner, and the hope is as it digests its food, it'll break down all the lipids into different fatty acids - some that can be used as nutrients for humans, as well as ones that can be used in chemical reactions to make a type of plastic for 3D printing.

But there's a lot of chemistry and genetic engineering that has to go into making this work.

For one thing, they'll need to engineer the yeast so it produces the fatty acids they want. For example, right now, the yeast makes a fat that's close to omega-3, but not quite. So, they'll add genes that rewire its chemistry to include the reactions that make omega-3.

Then, they'll engineer the yeast to make more of the fats, because right now, they don't make enough to be useful. So, the team will splice out the genes for the processes that the yeast doesn't really need to be doing in its job as a fatty-acid factory, and replace them with genes that encourage it to make more of those useful fats.

Another one of the projects led by researchers from Washington University in St. Louis is also trying to make something useful out of human waste, but this time, they're turning carbon dioxide into protein-based materials and they're planning to use cyanobacteria to do it. Cyanobacteria are great for space travel because they don't need much to live - feed them carbon dioxide and they'll grow, even in extreme environments, but there are challenges here too.

The bacteria already make some kinds of proteins as they grow, but they'll have to be engineered to produce the right kinds, and in a way that they're stable and don't immediately break down into something else. Then, the cells have to be engineered to recognise the proteins as waste and excrete them, because normally they'd just break them down and use them for energy. Once that's done, the researchers will engineer the bacteria to make lots and lots of protein.

These projects are still in the very earliest stages but someday, astronauts might be farming yeast and cyanobacteria for nutrients, plastics and proteins, all because they pee and breathe. So, we talked about how to recycle before and during a mission, but what about after a mission is complete? It turns out that there are still opportunities to reuse spacecraft floating around in space at that point in their journey.

For example, the Deep Impact spacecraft was able to go on a second exoplanet discovery mission after successfully smashing into a comet.

Here's how that spacecraft and 4 others got a new lease on life.

Space missions don't always go quite as planned and by the time something goes wrong, your spacecraft is a hundred million kilometers from home - too far away to dash out and repair it. Consequently, space science can get improvisational. If a tool is no longer capable of carrying out its original purpose, maybe it can still do something. Your adjustable wrench's threads are bound up? Now, you've got a normal wrench. Oh, it's stuck closed entirely? Well, now you've got a very oddly shaped hammer. The folks at NASA have had to apply this school of thought to far more sophisticated equipment and sometimes, it works out really well for them. Here are just a few examples: The Hubble Space Telescope has been serviced by astronauts 5 times since 1990, but it's the exception. Because it's in low earth orbit, we've actually been able to go there and fix it.

Other telescopes are less lucky. The Kepler Space Telescope was meant to find exoplanets by continually watching faraway stars for "transit events," a slight dimming of a star's brightness for a specific amount of time, indicating that a planet is passing in front of it. Through this method, Kepler aimed identify as many Earth-sized exoplanets as possible while looking at a patch of about 150,000 stars. It had four gyroscopic stabilizers: one stabilizer for each three-dimensional axis, plus a spare, if one of them should fail. These were to protect the probe from being pushed around too much by pressure from the solar wind.

In 2013, four years into the mission, two of the stabilizers failed, which made it too hard to keep the telescope steady. So NASA put it into sleep mode and went back to the drawing board. After a few months of hard work, scientists realized they could use the solar wind instead of fighting it.

Basically, bracing the spacecraft against it and using the other two gyros to keep it in place.

It would mean they'd need to re-align the telescope every 80 days as it orbited the sun and slowly shifted its angle relative to the solar wind, which meant pointing it at a new field of stars every few months, instead of studying the same patch continuously. But these limited campaigns returned fantastic results -- and buckets of exoplanets for researchers here at home.

And this isn't the only telescope NASA's had to save. Spitzer is an infrared space telescope designed to operate slightly above absolute zero to see distant objects that optical telescopes can't, such as low-temperature and dim objects far away. Spitzer initially had a life expectancy of two and a half years, which it easily outstripped.

But in 2009, after five and a half years of operating, its liquid helium coolant finally ran out. Spitzer could no longer look at some of the very cool and dim objects it'd been designed to spot. But at its new temperature, the telescope could still look at asteroids and comets in our own solar system, as well as far-off, ancient galaxies.

This was the start of its so-called "warm mission," which at -241 degrees, was still pretty chilly. As a result of this repurposing, Spitzer has subsequently observed countless amazing objects in our own solar system, and it's expected to keep going into 2020.

But space missions obviously aren't all about looking at things from afar. Sometimes, we want to get up close and personal. To that end, the Deep Impact Mission was designed to slam a probe into a comet while the probe's mothership watched.

In 2005, the 370 kg Impactor probe successfully smashed into comet Tempel 1 at 37,000 kilometers per hour, and in doing so, revealed a lot about the nature of comets. The mission complete, but while the probe had very much crash

landed, there was a still a perfectly functional mothership out there.

So mission managers sent it to do more cool comet science elsewhere. During its new mission, dubbed EPOXI, the probe flew by another comet, made observations of Earth and Mars, and even searched for exoplanets. Eventually, though, NASA lost contact in August 2013.

Then, there's the part where NASA used a totally different probe to get more mileage out of Deep Impact's results. The Stardust spacecraft, which flew through the tail of comet Wild 2 in 2004, was similarly successful enough to be given new tasks. One of these was a flyby of Tempel 1. Stardust's visit in 2011 gave NASA the opportunity to observe their handiwork and to make further observations of the unfortunate comet.

And, while we've covered it before, no discussion of spacecraft doing more than their planned workload would be complete without a mention of the Mars rover Opportunity. Oppy lasted 60 times longer than its planned lifetime of 90 days, spending nearly 15 years searching for signs of water and collecting other data on the red planet.

Opportunity is a pretty extreme example, but its success speaks to the careful planning and engineering that goes into every device we launch into space. Space travel is difficult and expensive, so the scientists responsible for it really care about getting it right. Whether it's coming up with clever fixes from afar or just making the most of their funding, scientists have gotten pretty adept at getting everything they can out of their outer space investments.

And those are just the spacecraft we reused while they were still in space! We've gotten to the point where some spacecraft can go to space, come back, and relaunch all over again. To learn more about reusable rocket technology, you can watch these SciShow Space videos about SpaceX's accomplishments. Thanks for watching these recycled SciShow videos about recycled space stuff!