News / Science & Technology

Electric Engines Keep Many Satellites in Orbit

This NASA image shows an artist rendering of the Juno spacecraft circling Jupiter.
This NASA image shows an artist rendering of the Juno spacecraft circling Jupiter.
George Putic

Among the challenges of deep-space travel is the amount of fuel needed for long flights. One of the solutions could be the electrical engine, powered by electricity from solar panels. Such engines already are in use aboard many satellites.

Physicists consider gravity a weak force. After all, we overcome its pull each morning when we get out of bed!

However, launching a satellite requires more effort: a large rocket and a lot of chemical fuel, which is quickly burned as it powers upward. Once the payload reaches about 160 kilometers above the earth, the effect of gravity has weakened enough for it to stay in orbit.

A one-way mission into deep space would require even more fuel, according to NASA senior technologist for space propulsion, Michael Patterson.

“For any mission application, particularly in deep space, the energy required to do the mission is huge, so the propellant fraction is typically quite large," he said.

Patterson said in the 1950s, the space agency started experimenting with so-called electric propulsion, or EP - - a jet of electrically charged particles that does not require too much power. Once in space, an EP-craft would keep gradually accelerating toward its destination, moving faster and faster the longer it travels. After four years, for example, it could be travelling at 10 kilometers a second.

Ion jets

That makes it ideal for long-range missions. But while NASA was testing EP for deep-space voyaging, engineers found another application for ion jets closer to our home planet.

The gravity of the sun, moon and earth constantly pull on geosynchronous commercial satellites, which stay in the same position relative to earth. Electric propulsion proved to be very useful for making sure that they stay in their required position.

Patterson says out of approximately 250 geosynchronous satellites in orbit today, about 43 percent have some form of EP on board.

Applications for deep space missions had to wait for another decade.

“It wasn’t until the 1990s where electric propulsion actually started being used by NASA for a NASA mission and that was with the advent if the ion thruster technology that was flown on the Deep Space One mission.”

Efficient propulsion

Scientists continue to experiment with other forms of propulsion that require even less energy. While NASA is developing the next generation ion propulsion system called NEXT, others are experimenting with more radical concepts, such as Q-Thruster, that uses radio-frequency microwaves instead of charged particle jets.

Critics call it “the impossible engine,” saying that the concept violates the basic principles of physics, while proponents say they have proof that it has actually generated thrust.

Patterson points out that EP is not appropriate for crewed missions in earth’s orbital environment or for travel to the moon, because it would take too long.

“Crossover point is in the kind of, Mars kind of destination, or beyond, meaning, if you have enough power on board it starts to possibly may make sense to use electrical propulsion for a crewed mission,” said Patterson.

He said for now, however, it would be reasonable to use EP for big unmanned vehicles taking cargo to Mars orbit, to support human infrastructure on the ground.





You May Like

Photogallery Belgian Security Measures Foreshadow New Normal for Europe

Rising threat of terrorism, disaffected Muslim populations and open borders, along with refugee, migrant crisis, are creating perfect storm for Europe, which some analysts fear continent is ill-suited to weather

Competing Claims of Responsibility for Mali Hotel Attack

Malian authorities ask public for help in identifying gunmen killed in attack, amid conflicting claims of responsibility from multiple jihadist groups active in the country

Video Debt-ridden Refugees Await Onslaught of Lebanese Winter

Aid agencies are attempting to reduce potentially devastating consequences of freezing conditions and snowstorms that killed eight last year, including three Syrian refugees

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
After Paris Attacks, France Steps Up Fight Against ISi
November 24, 2015 3:04 AM
The November 13 Paris attacks have drawn increased attention to Syria, where many of the suspected perpetrators are said to have received training. French President Francois Hollande is working to build a broad international coalition to defeat Islamic State in Syria and in Iraq. Zlatica Hoke reports.

Video After Paris Attacks, France Steps Up Fight Against IS

The November 13 Paris attacks have drawn increased attention to Syria, where many of the suspected perpetrators are said to have received training. French President Francois Hollande is working to build a broad international coalition to defeat Islamic State in Syria and in Iraq. Zlatica Hoke reports.

Video US, Cambodian Navies Pair Up in Gulf of Thailand

The U.S. Navy has deployed one of its newest and most advanced ships to Cambodia to conduct joint training drills in the Gulf of Thailand. Riding hull-to-hull with Cambodian ships, the seamen of the USS Fort Worth are executing joint-training drills that will help build relations in Southeast Asia. David Boyle reports for VOA from Preah Sihanouk province.

Video Americans Sharpen Focus on Terrorism

Washington will be quieter than usual this week due to the Thanksgiving holiday, even as Americans across the nation register heightened concerns over possible terrorist threats. VOA’s Michael Bowman reports new polling data from ABC News and the Washington Post newspaper show an electorate increasingly focused on security issues after the deadly Islamic State attacks in Paris.

Video World Leaders Head to Paris for Climate Deal

Heads of state from nearly 80 countries are heading to Paris (November 30-December 11) to craft a global climate change agreement. The new accord will replace the Kyoto Protocol on Climate Change that expired in 2012.

Video Uncertain Future for Syrian Refugee Resettlement in Illinois

For the trickle of Syrian refugees finding new homes in the Midwest city of Chicago, the call to end resettlement in many U.S. states is adding another dimension to their long journey fleeing war. Organizations working to help them integrate say the backlash since the Paris attacks is both harming and helping their efforts to provide refugees sanctuary. VOA's Kane Farabaugh reports.

Video Creating Physical Virtual Reality With Tiny Drones

As many computer gamers know, virtual reality is a three-dimensional picture, projected inside special googles. It can fool your brain into thinking the computer world is the real world. But If you try to touch it, it’s not there. Now Canadian researchers say it may be possible to create a physical virtual reality using tiny drones. VOA’s George Putic reports.

Video New American Indian Village Takes Visitors Back in Time

There is precious little opportunity to experience what life was like in the United States before its colonization by European settlers. Now, an American Indian village built in a park outside Washington is taking visitors back in time to experience the way of life of America's indigenous people. Carol Pearson narrates this report from VOA's June Soh.

Video Even With Hometown Liberated, Yazidi Refugees Fear Return

While the northern Iraqi town of Sinjar has been liberated from Islamic State forces, it's not clear whether Yazidi residents who fled the militants will now return home. VOA’s Mahmut Bozarslan talked with Yazidis, a religious and ethnic minority, at a Turkish refugee camp in Diyarbakır. Robert Raffaele narrates his report.

Video Nairobi Tailors Make Pope Francis’ Vestments

To ensure the pope is properly attired during his visit, the Kenya Conference of Catholic Bishops asked the Dolly Craft Sewing Project in the Nairobi slum of Kangemi to make the pope's vestments, the garments he will wear during the various ceremonies. Jill Craig reports.

Video Cross-Border Terrorism Puts Europe’s Passport-Free Travel in Doubt

The fallout from the Islamic State terror attacks in Paris has put the future of Europe’s passport-free travel area, known as the "Schengen Zone," in doubt. Several of the perpetrators were known to intelligence agencies, but were not intercepted. Henry Ridgwell reports from London European ministers are to hold an emergency meeting Friday in Brussels to look at ways of improving security.

Video El Niño Brings Unexpected Fish From Mexico to California

Fish in an unexpected spectrum of sizes, shapes and colors are moving north, through El Niño's warm currents from Mexican waters to the Pacific Ocean off California’s coast. El Nino is the periodic warming of the eastern and central Pacific Ocean. As Faiza Elmasry tells us, this phenomenon thrills scientists and gives anglers the chance of a once-in-a-lifetime big catch. Faith Lapidus narrates.

Video Terrorism in Many Forms Continues to Plague Africa

While the world's attention is on Paris in the wake of Friday night's deadly attacks, terrorism from various sides remains a looming threat in many African countries. Nigerian cities have been targeted this week by attacks many believe were staged by the violent Islamist group Boko Haram. In addition, residents in many regions are forced to flee their homes as they are terrorized by armed militias. Zlatica Hoke reports.

Video Study: Underage Marriage Rate Higher for Females in Pakistan

While attitudes about the societal role of females in Pakistan are evolving, research by child advocacy group Plan International suggests that underage marriage of girls remains a particularly big issue in the country. VOA’s Ayesha Tanzeem reports how such marriages leads to further social problems.

VOA Blogs