How Micrometeoroid Impacts Pose a Danger for Today’s Spacewalk



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Our very own International Space Station is in the cosmic crosshairs.

As cosmonauts are to begin Extra Vehicular Activity (EVA) this morning to perform routine maintenance, an article reminding us of the hazards of such activity came to us via NASA’s Orbital Debris Quarterly Newsletter.

The problem is Micrometeoroid and Orbital Debris (MMOD) impacts. These are nothing new. Pits and tiny cratering has been observed during post-flight inspections of space shuttle orbiters. But this is the first time we’d seen talk of damage caused by tiny impacts on the exterior of the International Space Station.

The handrails are a particularly sensitive area of concern.

The study examined damage incurred on handrails exposed to the environment of space for years on end. These present a hazard to spacewalking astronauts who rely on the handles to move about. These craters often become spalled, presenting a sharp metal rim raised from the surface of the handle.

Close-up of a micro-meteoroid impact on a handrail. (Credit: NASA/JSC Image & Science Analysis Group).
Close-up of a micro-meteoroid impact on a handrail. (Credit: NASA/JSC Image & Science Analysis Group).

Of course, these razor sharp rims present a problem, especially to space suit gloves. One 34.8 centimeter long handrail returned on the final Space Shuttle mission STS-135 had six impact craters along its length. The handrail had been in service and exposed to the vacuum of space for 8.7 years.

Craters as large as 1.85 millimetres (mm) in diameter with raised lips of 0.33mm have been observed on post-inspection. In studies conducted by NASA engineers, craters with lip heights as little as 0.25mm have been sufficient to snag and tear spacesuit gloves.

There have also been reported incidents of glove tears during EVAs conducted from the ISS over the years. For example, the report cites a tear noticed by astronaut Rick Mastracchio during STS-118 that cut the EVA short.

Analysis of an impact seen on STS-122. (Credit: NASA
Analysis of an impact seen on STS-122. (Credit: NASA/JSC Image & Science Analysis Group).

To protect astronauts and cosmonauts during EVAs, the following measures have been instituted:

–          Toughening space suit gloves by adding reinforcement to areas exposed to potential MMOD damage.

–          Monitoring and analyzing MMOD impacts along handrails and maintaining a database of problem areas.

–          Equipping spacewalkers with the ability to cover and/or repair hazardous MMOD areas during spacewalks.

The studies were carried out by the Johnson Space Center Hypervelocity Impact Technology Group in conjunction with a test facility at White Sands, New Mexico. Astronaut Rick Mastracchio can also be seen talking about the hazards of spacewalking on this video.

Today’s 6 hour EVA by cosmonauts Vinogradov & Romanenko begins at 14:06 UT 10:06AM EDT.

This will be the 32nd Russian EVA from the International Space Station and will use the Pirs hatch on Zvezda.

Tasks include retrieving and installing experiment packages and replacing a defective retro-reflector device on the station’s exterior.  The device is a navigational aid necessary for the Albert Einstein ATV-4 mission headed to the ISS on June 5th.

Progress 51P is also scheduled to launch towards the ISS next week on April 24 for docking on April 26th.

Debris in Low Earth Orbit is becoming an increasing concern. The Chinese anti-satellite test in 2007 and the collision of Kosmos 2251 and Iridium 33 in 2009 have increased hazards to the ISS. Many fear that a tipping point, known as an ablation cascade, could eventually occur with one collision showering LEO with debris that in turn trigger many more. The ISS was only finished in 2011, and it would be a tragic loss to see it abandoned due to a catastrophic collision only years after completion.

More than once, ISS crew members have sat out a debris conjunction that was too close to call in their Soyuz life boats, ready to evacuate the station if necessary. DAMs (Debris Avoidance Maneuvers) are now common for the ISS throughout the year.

Several ideas have been proposed to deal with space debris. In the past year, NanoSail-2D demonstrated the ability to deploy a solar sail from a satellite for reentry at the end of a spacecraft’s life span. Such technology may be standard equipment on future satellites.

Expect reentries to increase as we near the solar maximum for cycle #24 in late 2013 & early 2014. This occurs because the exosphere of Earth “puffs out” due to increased solar activity and increases drag on satellites in low Earth orbit.

All food for thought as we watch today’s EVA… space travel is never routine!

The April 2013 edition of the Orbital Debris Quarterly News is available for free online.

 

Space Debris Threat May Require Avoidance Maneuver for Space Station

UPDATE (9/27/2012, 13:00 UTC) NASA now says that with additional tracking, they have determined the two pieces of space debris do not pose a threat to the ISS, and a debris avoidance maneuver scheduled for Thursday morning was cancelled by the flight control team at Mission Control. The ATV undocking time on Friday is still being decided at the time of this posting. See additional info at NASA’s website. (End of update)

International Space Station officials are keeping a watchful eye on two different pieces of space junk that may require the ISS to steer away from potential impact threats. Debris from the Russian COSMOS satellite and a fragment of a rocket from India may come close enough to the space station to require a debris avoidance maneuver. If needed, the maneuver would be done using the ESA’s Automated Transfer Vehicle (ATV) “Edoardo Amadi.” The ATV was supposed to undock last night, but a communications glitch forced engineers to call off the departure.

Both pieces of debris are edging just inside the so-called “red zone” of miss distance to the station with a time of closest approach calculated to occur Thursday at 14:42 UTC (10:42 a.m. Eastern time.) It is not known how large the object is.

An approach of debris is considered close only when it enters an imaginary “pizza box” shaped region around the station, measuring 1.5 x 50 x 50 kilometers (about a mile deep by 30 miles across by 30 miles long) with the vehicle in the center.

NASA says the three-person Expedition 33 crew is in no danger and continues its work on scientific research and routine maintenance. The current crew includes NASA astronaut Sunita Williams, Japanese astronaut Akihiko Hoshide and Russian cosmonaut Yuri Malenchenko.

If the maneuver is required – and NASA said it could be called off any time — it would occur at 12:12 UTC (8:12 a.m. EDT) Thursday, using the engines on the ATV, which remains docked to the aft port of the Zvezda Service Module. It usually takes about 30 hours to plan for and verify the need for an avoidance maneuver.

Debris avoidance maneuvers are conducted when the probability of collision is greater than 1 in 100,000, if it will not result in significant impact to mission objectives. If it is greater than 1 in 10,000, a maneuver will be conducted unless it will result in additional risk to the crew.

Only three times during the nearly 12 years of continual human presence on the ISS has a collision threat been so great that the crew has taken shelter in the Soyuz vehicles. (Those events occured on March 12, 2009, June 28, 2011 and March 24, 2012.) During those events, the station was not impacted. While the ISS likely receives small micrometeoroid hits frequently (based on experiments left outside the ISS and visual inspections of the station’s hull) no large debris impacts have occurred that have caused depressurization or other problems on the ISS.

Tuesday’s initial attempt to undock the ATV was called off due to a communications error between the Zvezda module’s proximity communications equipment and computers on the ATV. Russian engineers told mission managers that they fully understand the nature of the error and are prepared to proceed to a second undocking attempt, which has been postponed to Friday at the earliest, due to the potential space debris threat.

Once it is undocked, the ATV will move to a safe distance away from the station for a pair of engine firings that will send the cargo ship back into the Earth’s atmosphere to burn up over the Pacific Ocean.

The ATV still has extra fuel on board, and so the decision was made that if need, that available resource would be used.

Here’s the info on NASA’s criteria for performing debris avoidance maneuvers.

Source: NASA

*this article has been updated

Spherical Object Drops from the Sky in Namibia

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Officials from Namibia have been examining a hollow ball that fell from the sky back in November 2011. So far, they haven’t had much luck identifying it, so have called in NASA and ESA, hoping the space agencies can provide some answers. The spherical object has a circumference of 1.1 meters (43 inches) and was found in a remote area in the northern part of the country, about 750 kilometers (480 miles) from the capital Windhoek, according to police forensics director Paul Ludik, quoted in an article by AFP.

Ludik described it as made of a “metal alloy known to man” (so cross alien spacecraft part off the list), weighing six kilograms (13 pounds).

This isn’t the first time balls from space have dropped in on unsuspecting countries.

Space spheres found in Australia and Brazil in 2008.

Back in 2008 spherical objects fell to Brazil and Australia, and there have been previous reports of similar objects, as well.

After some post-crash forensics, the two objects in 2008 were identified the as a Composite Overwrapped Pressure Vessel (or COPV), which were carried on the space shuttles, and are a high pressure container for inert gases. COPVs have been used for a variety of space missions.

They are built with a carbon fiber or Kevlar overcoat to provide reinforcement against the vast pressure gradient between the inside and outside of the container, and so can survive re-entry through Earth’s atmosphere.

Composite Pressure Vessels. Credit: NASA

The one in Namibia was found 18 meters from its landing spot – it created a mini-crater 33 centimeters deep and 3.8 meters wide.

Other suggestions of what the object could be is a piece from a space gyroscope, a satellite part, a tank from one of the Apollo missions, or a part of a Russian spacecraft, (which have been known to crash to the ground, as well)

Sources: PhysOrg, NASA, and thanks to Ian O’Neill for his previous and current articles on this subject

Look Out Below! Huge Satellite Coming in for Uncontrolled Re-Entry

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There’s a defunct 6.5-ton satellite heading our way. Trouble is, NASA’s not sure exactly where and when it might come down. And they’re not sure how much of it might survive its fiery fall through Earth’s atmosphere, either.

“Numerically, it comes out to a chance of 1-in-3,200 that one person anywhere in the world might be struck by a piece of debris,” said Nick Johnson, chief scientist with NASA’s Orbital Debris Program, during a media teleconference on Friday. “Those are obviously very, very low odds that anybody’s going to be impacted by this debris.”

Johnson reminded everyone that “throughout the entire 54 years of the space age, there have been no reports of anybody in the world being injured or severely impacted by any re-entering debris.”

How do you like your odds?

The huge 10-meter (35-ft) -long Upper Atmosphere Research Satellite (UARS) is in an orbit that crosses over six continents and three oceans. Johnson said it is expected to re-enter Earth’s atmosphere in an uncontrolled fall in late September or early October. While much of the spacecraft is expected to burn up during re-entry, it’s likely some pieces will make it to the ground. Current projections on where debris field might be is a 800-km- (500-mile) wide swath from Northern Canada to Southern South America.

Yikes.

Or it might fall in the ocean.

“We do know with 99.9 percent accuracy that it will re-enter the atmosphere somewhere between 57 degrees north and 57 degrees south, which means it will be anywhere from northern Canada to southern South America,” said Major Michael Duncan, deputy chief of space situational awareness with the Air Force’s U.S. Strategic Command. “That is truly the best estimation we can give you at this point in time.”

There are about 26 components that are big enough to survive and make it down to Earth, the largest weighing more than 150 kg (330 pounds.)

But hey, this happens all the time.

“Satellites re-entering is actually very commonplace,” Johnson said. “Last year, for example, we averaged over one object per day falling back uncontrolled into the atmosphere,” and for those coming back in an uncontrolled fashion – meaning it is a crapshoot when and where they fall — there were 75 metric tons of spacecraft and rocket bodies falling back to Earth.

“In perspective, UARS is less than six metric tons,” Johnson added. “So it’s a very small percentage of the annual re-entry of satellites.”

The majority of these satellites, though, were a lot smaller than UARS and they burn up completely in the atmosphere.

The UARS satellite launched from Space Shuttle Discovery in 1991. To give you an idea of how big the satellite is, it filled the shuttle’s payload bay completely. It had ten science instruments to examine the chemistry of the upper atmosphere and measure water vapor and other elements. It monitored the health of the ozone hole, looking at the amounts of aerosols in the atmosphere. In 2005 NASA determined that UARS was to be decommissioned.

It was never designed to be returned on the Space Shuttle, said Paul Hertz, chief scientist, NASA’s Science Mission Directorate.
Hertz said NASA is trying to keep the public informed about the the possibilities of debris failing and want to be up front about it. They will post all current information on www.nasa.gov/uars.

And Space Command will be tracking the satellite and providing updates as to where and when UARS will come down, and provide impact predictions if it looks like it will be coming down over land.

Although there are no hazardous materials on board – unlike the hydrazine on a National Reconnaissance Office spy satellite that was shot down in 2008 to avoid contaminating Earth – it was stressed that if anyone finds a piece of the satellite, they should not pick it up, but notify the local authorities.

But anyone along the final trajectory should get “a nice show,” Johnson said.

“It is a relatively large vehicle,” he said. “It would be visible in daylight. Odds are, though, it’s going to happen over an ocean, unlikely to be seen unless it’s by an airliner. We’ve had reports like that before. Since we don’t know where it’s going to come in, we can’t raise people’s expectations and tell them to go out and look in their backyard. So it’ll be a serendipitous kind of event.”

Space Debris Problem Getting Worse, New Report Says

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In the movie WALL-E, the Earth is surrounded by a dense field of orbiting junk. The problem of space debris is not that bad yet, but is potentially heading in that direction. A new report released today by the National Research Council says the problem of space debris is getting worse and has passed a “tipping point.” The report says that while NASA has done a good job using their available resources to research the issue, decreased funding and increased responsibilities for the space agency is not a good combination for the future, and NASA has not been able to keep pace with increasing hazards posed by abandoned equipment, spent rocket bodies, and other debris orbiting the Earth.

“The current space environment is growing increasingly hazardous to spacecraft and astronauts,” said Donald Kessler, chair of the committee that wrote the report and retired head of NASA’s Orbital Debris Program Office. “NASA needs to determine the best path forward for tackling the multifaceted problems caused by meteoroids and orbital debris that put human and robotic space operations at risk.”

There’s enough debris currently in orbit to continually collide and create even more debris, raising the risk of spacecraft failures, the report notes. In addition, collisions with debris have disabled and even destroyed satellites in the past, as in the collision in 2009 between an Iridium satellite and a inoperative Russian satellite. Several recent near-misses of the International Space Station requiring evasive maneuvers and sending astronauts to the Soyuz vehicles as a precaution underscores the value in monitoring and tracking orbital debris as precisely as possible.

It is fitting that Kessler lead this committee: he laid out a scenario back in 1978 called the Kessler Syndrome where the amount and size of objects in Earth’s orbit could eventually become so large that they would continually collide with one another and create even more debris, eventually causing a “cascade” of collisions which could make low Earth orbit unusable for decades.

From the new report, it appears the Kessler Syndrome is not just an abstract event that might occur in the future. It’s happening now. The amount of debris is now growing exponentially, as just two collisions since January 2007 has doubled the total number of debris fragments in Earth’s orbit, according to the NRC report.

NASA had asked for the report; specifically, NASA’s chief of safety and mission assurance, Bryan O’Connor, asked the NRC in 2010 to independently examine the agency’s work on debris.

“We thank the National Research Council for their thorough review in this report,” said NASA spokeswoman Beth Dickey. “We will study their findings and recommendations carefully and use them to advise our future actions in this important area of work.”

The report, however, does not provide NASA with many specific ideas but says NASA should develop a formal strategic plan to better allocate its limited resources devoted to the management of orbital debris. In addition, removal of debris from the space environment or other actions to mitigate risks may be necessary.

For example, NASA should initiate a new effort to record, analyze, report, and share data on spacecraft anomalies. This will provide additional knowledge about the risk from debris particulates too small to be cataloged under the current system yet large enough to potentially cause damage.

The report also suggests more work internationally on this problem, since it is a global problem caused by other nations besides the US. Over the past decade and a half, the world’s major space agencies have been developing a set of orbital debris mitigation guidelines aimed at stemming the creation of new space debris and lessening the impact of existing debris on satellites and human spaceflight. Most agencies are in the process of implementing or have already implemented these voluntary measures which include on-board passive measures to eliminate latent sources of energy related to batteries, fuel tanks, propulsion systems and pyrotechnics.

But the growing number of developing countries that are launching using satellites, and they need to be encouraged to use these measures as well.

In addition, NASA should lead public discussion of orbital debris and emphasize that it is a long-term concern for society that must continue to be addressed.

Congress also needs to be aware of the problem and provide adequate funding for the issue.

You can read the report here. (free as a pdf download).

Sources: NRC press release, Washington Post

Space Junk Forces ISS Crew to Takes Shelter in Soyuz

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The six crewmembers on board the International Space Station were told to take shelter in the two Russian Soyuz spacecraft early Tuesday because Space Command predicted a piece of space junk could make a close approach to the station. Radar tracking indicated the debris would make its close pass at 8:08 a.m. EDT (12:08 UTC), coming within about 243 meters (800 feet) of the station and well within the “pizza box” -shaped area around the ISS, but when no impact was detected the crew was told they could reenter the station and resume normal operations.

NASA’s Chief Scientist for Orbital Debris Nicholas L. Johnson told Universe Today during a previous “conjuction” of space debris and the ISS that on average, close approaches to ISS occur about three times a month. An approach of debris is considered “close” only when it enters an imaginary “pizza box” shaped region around the station, measuring 0.75 kilometers above and below the station and 25 kilometers on each side( 2,460 feet above and below and 15.6 by 15.6 miles).

Johnson said that small pieces of debris have already collided with ISS on many occasions, but these debris to date have not affected the safety of the crew or the operation of the mission. “The dedicated debris shields on ISS can withstand particles as large as 1 cm in diameter,” he said.

The piece of space junk was detected too late for the station to perform an evasive maneuver, so the crew was told to “shelter in place” on the two Soyuz spacecrafts. The crew on board is commander Andrey Borisenko, Alexander Samokutyaev and Ronald Garan, who took shelter aboard the Soyuz TMA-21 spacecraft docked to the Poisk module, and Sergei Volkov, Michael Fossum and Furukawa who went on to the Soyuz TMA-02M spacecraft docked to the Rassvet module.

Russia Wants to Build “Sweeper” to Clean up Space Debris

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Russia is looking to build a $2 billion orbital “pod” that would sweep up satellite debris from space around the Earth. According to a post on the Russian Federal Space Agency, Roscosmos’ Facebook site, (which seems to confirm an earlier article by the Interfax news agency) the cleaning satellite would work on nuclear power and be operational for about 15 years. The Russian rocket company, Energia proposes that they would complete the cleaning satellite assembly by 2020 and test the device no later than in 2023.

“The corporation promises to clean up the space in 10 years by collecting about 600 defunct satellites on the same geosynchronous orbit and sinking them into the oceans subsequently,” Victor Sinyavsky from the company was quoted as saying.

Sinyavsky said Energia was also in the process of designing a space interceptor that would to destroy dangerous space objects heading towards the Earth.

No word on exactly how the space debris cleaner would work, of how it would push dead satellites and other debris into a decaying orbit so that objects would burn up in the atmosphere, or if it might somehow gather up or “vacuum” debris. But at least someone is thinking about space debris and asteroid deflection and putting more than just a few rubles (60 billion of ’em) towards these concepts.

Sources: Xinhuanet, Facebook

New Satellite for Monitoring Space Debris To Launch

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The U.S. Air Force will launch the first-ever satellite dedicated solely to tracking the positions of other satellites and the thousands of pieces of space debris in Earth orbit. The $500 million Space-Based Space Surveillance satellite, scheduled for a July 8 launch from Vandenberg Air Force Base, in California, will continuously monitor the “traffic” around the Earth, providing an unobstructed view day or night. Currently, the ground-based radar and optical telescopes used to track satellites and space junk can only be used on clear nights, and not all the observatories are powerful enough to detect objects in high or geosynchronous orbits.

This is the first satellite in the SBSS System that will eventually lead to a constellation of satellites to detect and track orbiting space objects, according to Boeing, the prime contractor for this first “Pathfinder” satellite. While the Air Force is the primary user of the SBSS satellites, the US Department of Defense will also use data from the eventual satellite system to support military operations, and NASA can use the information to calculate orbital debris collision-avoidance measures for the International Space Station and Space Shuttle missions.

The Air Force estimates there are about 1,000 functioning satellites and about 20,000 pieces of debris orbiting Earth.

The new satellite will be in orbit 627 kilometers (390 miles) above the Earth, and has an optical camera on a swivel mount, so the camera’s view can be changed without burning fuel to move the satellite, and will concentrate on satellites and debris in deep space. The information from the satellite will be sent to a command center at Schriever Air Force Base in Colorado.

The Air Force space surveillance network previously had partial use of a satellite called the Midcourse Space Experiment, which was designed to track missiles but could also monitor objects in orbit. It’s no longer functioning.

Right now, the Air Force can detect objects as small as 10 centimeters across, or about 4 inches, and they have not released information on the the capabilities of the new satellite.

The Secure World Foundation says there could be millions of pieces of debris in total around the Earth. Debris at altitudes above several hundred kilometers can stay in orbit for decades or even centuries, and those about 1,500 kilometers will remain in orbit for thousands of years. Even very small particles of space debris can have a devastating effect on anything they hit because of their high relative impact velocities.

Chart of orbital debris. Source: NASA Orbital Debris Quarterly News, April 2009,

This chart displays a summary of all objects in Earth orbit officially cataloged by the U.S. Space Surveillance Network. “Fragmentation Debris” includes satellite breakup debris and anomalous event debris, while “Mission?related Debris” includes all objects dispensed, separated, or released as part of the planned mission. Note the dramatic increase in fragmentation debris caused by the Chinese ASAT test conducted in January 2007. Another smaller increase is noted following the 2009 collision between an Iridum communications satellite and a non-functioning Russian satellite.

It is hoped the new SBSS satellite will increase the capabilities to help avoid future collisions.

Sources: Boeing, Secure World Foundation, AP

Climate Change Contributes to Space Junk Problem

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The effects of climate change can be seen across the majority of the planet, but a new study reveals it is also affecting the space environment. New Scientist reports that increased carbon dioxide levels are cooling the upper atmosphere, which decreases the atmospheric density. This in turn affects how long defunct satellites, spent rocket boosters and other space debris stay in orbit, contributing to the space junk problem.

Atmospheric drag creates a braking effect on space debris, and eventually causes the various bits and pieces to drop out of orbit and burn up. Two researchers at the University of Southampton in the UK, Arrun Saunders and Hugh Lewis, studied the orbits of 30 satellites over the past 40 years, and recorded a gradual increase in the time they remain in orbit.

They calculated that at an altitude of 300 kilometers, the atmosphere is reducing in density by 5 per cent every decade. “The lower molecular braking means debris can remain in orbit up to 25 per cent longer,” said Lewis.

This raises the risk of collisions with satellites and makes it more hazardous to launch spacecraft. Space agencies and commercial launch companies may need to step up the current space debris mitigation procedures now in place, which include employing on-board passive measures to eliminate the potential for explosions from batteries, fuel tanks, propulsion systems and pyrotechnics, which helps reduce the number of objects in orbit. Or we may need to find a way to remove debris from orbit sooner rather than later.

Saunders and Lewis presented their work at a conference in Boulder, Colorado, last week.

Source: New Scientist

Plasma Rocket Could Help Pick Up Space Trash

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Franklin Chang Diaz’s proposed VASIMR rocket engine could create very versatile spacecraft. Not only does the plasma-fueled rocket have the potential to make a trip to Mars in just over a month, it could also help clean up space trash in Earth orbit. “Our goal is to be able to have a garbage truck that will be picking up all of these objects at various orbits,” astronaut Chang Diaz said in an article in the Global Post. The debris could put into an “orbital graveyard,” he added, “or we could actually launch them to the sun and drive them to the sun, which is kind of the ultimate, cosmic dump.”

Image plot of space junk. Image credit: NASA
Image plot of space junk. Image credit: NASA

Space debris is becoming a growing problem. The number of non-operating satellites in orbit has increased, as well as debris from spacecraft explosions and, as happened earlier this year, collisions between satellites.

“The Earth has become virtually a beehive,” Chang Diaz said. “The number of satellites orbiting the Earth, we’re talking hundreds of thousands of these objects. Some of them are just junk that’s floating there simply because these satellites have run out of fuel and they just remain in orbit dead.”

The rocket, called the VASIMR for “variable specific impulse magnetoplasma rocket,” uses a high-power technology initially studied by NASA that turns argon into plasma. Propelled by an exhaust gas at temperatures close to that of the sun, the VASIMR VX-200 engine would have the ability to change orbits and accelerate and decelerate in order to pick up space debris.

In September, Chang Diaz’s company, Ad Astra, tested the rocket and achieved a milestone. During the a test on in a vacuum chamber on Earth, the engine cranked at just over 200 kilowatts, becoming the world’s most powerful electric rocket.

Possible uses for the VASIMR rocket. Credit: Ad Astra
Possible uses for the VASIMR rocket. Credit: Ad Astra

VASIMR is not suitable to launch payloads from the surface of the Earth due to its low thrust to weight ratio and its need of a vacuum to operate. It would, however be ideal to function as an upper stage for cargo, drastically reducing the fuel requirements for in-space transportation.

Ad Astra has also signed an agreement with NASA to test a 200-kilowatt VASIMR engine on the International Space Station in 2013 to help keep it in orbit. ISS boosts are currently provided by conventional thrusters, which consume about 7.5 tons of propellant per year. By cutting this amount down to 0.3 tons, Chang-Diaz estimates that VASIMR could save NASA millions of dollars per year.

Other uses of the plasma rocket engine would be lunar cargo transport, human missions to Mars or other destinations, and in-space refueling.

Sources: Global Post, Ad Astra