What goes up doesn’t always come down We have been going into space for almost 50 years A lot of things have gone up

Some things have come back to Earth They have landed or burned up in the atmosphere, lighting up the sky much like a meteor Some have gone on to explore other worlds or space But a lot of things are still in orbit A 500 pound satellite tank landed in a yard in Texas missing a house by 50 yards Saturn V rocket from the Apollo mission to the Moon in Earth orbit since 1969 Meteors (from space junk?) Parts of a Delta 2 rocket fell in South Africa

There are approximately space junk re- entries each year In 2006 a woman in Tulsa, Oklahoma was hit, but not injured, by a small piece of charred metal mesh that was later confirmed to be part of a Delta II rocket launched in 1996 But the risk that a person will be hit and injured by falling space junk is less than one in 1 trillion HARD HAT AREA?

There is a lot of junk still going around the Earth It can be as small as a dot of paint that came off a spacecraft It can be as big as a spacecraft that has stopped working There are about 500 working spacecraft in orbit that must be protected A piece of space junk falls through the sky (NASA)

Space Debris in general (debris can have extraterrestrial origins as well) can be moving at speeds up to 22,000 miles an hour It means that even a small piece can cause a lot of damage to the Space Shuttle or the International Space Station It can cripple satellites worth hundreds of millions of dollars It can damage research satellites (such as the Hubble Space Telescope) And it can even kill astronauts Tiny hole in the Space Shuttle Atlantis caused by space debris (NASA) Damage to the Hubble solar panel from space debris (ESA)

This year, after a half- century of growth, the federal list of orbiting detectable objects (4 inches wide or larger) reached 10,000 This increases the risk of large pieces smashing into each other, breaking into hundreds of pieces and creating a slow cascade of collisions that could create chaos and threaten satellites and future human space travel

Astronauts have accidentally contributed to the litter In 1965 Ed White, part of the Gemini 4 mission, lost a spare glove on his first spacewalk The glove lost by Ed White orbited Earth with a speed of 28,000 km/hour, becoming the most dangerous garment in history Ed White making his historic spacewalk in 1965 (NASA)

In July 2006 astronaut Piers Sellers reported that he lost a spatula (it is nicknamed “spatsat”) In 2006 a couple of bolts “escaped” as astronauts were adding a part to the ISS (at 17,000 mph even a small bolt can hit a space shuttle with the impact of a hand grenade) The oldest piece of space junk still in orbit is the second U.S. satellite, Vanguard I, launched on March 17, 1958, which worked for only 6 years Vanguard I satellite (NASA) The spatula before it floated away. It was used to repair damaged heat shield tiles (NASA)

Most of the objects that re- enter the Earth’s atmosphere burn up or fall into the ocean The most spectacular re-entry was Skylab, the U.S. space station that was launched in 1973 Most of it splashed down in the Indian Ocean in 1979, but some landed in sparsely populated western Australia No one was injured but the U.S. Dept of State received a $400 fine for littering from the town of Esperance, Australia Skylab (NASA)

In 2001 the Russian space station Mir spectacularly re- entered the Earth’s atmosphere and landed in the South Pacific Observers in Fiji saw 5 extremely bright object crossing the sky and a series of sonic booms Mir burns up in the sky near Fiji Mir (ESA)

On January 4, 2007 at 6:13am the body of a Russian booster rocket broke up as it re-entered the atmosphere over Colorado & Wyoming NORAD said it was an SL-4 rocket used to launch a French space telescope, COROT, in December The light was described as having an extremely bright head with a tail that emitted sparks or smoke Photo from Fox 31 News, Denver

China’s test on January 11, 2007 of an anti-satellite (ASAT) rocket shattered an old weather satellite into thousands of large fragments This is the worst such episode in space history Today, next year, or next decade some of this debris may start a cascade of collisions that may expand for centuries, putting billions of dollars of advanced satellites at risk View of ISS orbit (green) and debris ring from the Chinese ASAT test (red) shows the debris may pose a risk to the Space Station (STK-generated image courtesy of CSSI)

There is an estimated 4 million pounds of space junk in low-Earth orbit There is roughly 110,000 objects larger than one centimeter—each big enough to damage a satellite or space-based telescope Although the U.S. and Russia lead the list of space junkers, other contributors include the European Space Agency, Japan, France, and India

Space agencies continue to monitor the debris in space as new objects are added every few days from launches, collisions and explosions As of now, there are no regulations controlling the generation of junk, only recommendations about minimizing it The U.S. Space Command monitors space debris and informs NASA and other agencies when there is a threat Earth Orbit is getting very crowded

Some ideas for protecting items in space have come from NASA’s Hypervelocity Impact Technology Facility They have developed many advanced shielding concepts that will be used on the ISS Some materials have better shielding capabilities than others and these are used in various combinations The side view of an impacted multi-shock shield with Nextel bumpers and a Kevlar rearwall (NASA)

One suggestion for taking care of space junk include a graveyard orbit where no operational satellites are present Another suggestion is taking satellites out of orbit at the end of their operational life This could be aided by an electrodynamic tether that would slow down a spacecraft using atmospheric drag to cause it to fall out of orbit after a few years Artist’s concept of a satellite with a tether

Proposals have been made to “sweep” with laser brooms to nudge small particles into decaying orbits Or huge aerogel blobs (low-density solid-state materials) to absorb junk and fall out of orbit Currently the most effort is in preventing collisions by keeping track of debris

For years we have known to protect our environment on Earth Now we know we have to protect the environment off the Earth