Let’s not sugarcoat it. Exploring the Moon is not for the faint of heart! It’s an airless body, which means there is no atmosphere, the surface temperatures are extreme, and there’s lots of radiation. The low gravity also means you can never really walk on the surface and have to bounce around in a bulky spacesuit until you fall over. And you can bet your bottom dollar people will make a supercut of the footage someday (see below). Then there’s that awful moondust (aka. lunar regolith), which is electrostatically charged and sticks to EVERYTHING!
Looking to take advantage of this, researchers from the Massachusetts Institute of Technology (MIT) began testing a new concept for a hovering rover that harnesses the Moon’s natural charge to levitate across the surface. On the Moon, this surface charge is strong enough to levitate moon dust more than 1 meter (3.3 ft) above the surface. With support from NASA, this research could lead to a new type of robotic exploration vehicle that will help astronauts explore the Moon in the coming years.
An artist's impression of the BepiColombo spacecraft as it approaches Mercury at the end of its 7 year journey. Image: spacecraft: ESA/ATG medialab; Mercury: NASA/JPL
A handful of spacecraft have used ion engines to reach their destinations, but none have been as powerful as the engines on the BepiColombo spacecraft. BepiColombo is a joint mission between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA.) It was launched on October 20, 2018, and has gone through weeks of in-flight commissioning. On Sunday it turned on its powerful ion thrusters for the first time.
“We put our trust in the thrusters and they have not let us down.” – Günther Hasinger, ESA Director of Science.
BepiColombo is a three-part spacecraft. It has two orbiters, the Mercury Planet Orbiter (MPO) built by the ESA, and the Mercury Magnetospheric Orbiter (MMO) built by JAXA. The third part is the Mercury Transfer Module (MTM), built by ESA. The MTM is the propulsion part of the spacecraft and contains the spacecraft’s four ion engines.
The comforting blue glow of an ion drive. Image Credit: NASA
When we think of space travel, we tend to picture a massive rocket blasting off from Earth, with huge blast streams of fire and smoke coming out the bottom, as the enormous machine struggles to escape Earth’s gravity. Rockets are our only option for escaping Earth’s gravity well—for now. But once a spacecraft has broken its gravitational bond with Earth, we have other options for powering them. Ion propulsion, long dreamed of in science fiction, is now used to send probes and spacecraft on long journeys through space.
NASA first began researching ion propulsion in the 1950’s. In 1998, ion propulsion was successfully used as the main propulsion system on a spacecraft, powering the Deep Space 1 (DS1) on its mission to the asteroid 9969 Braille and Comet Borrelly. DS1 was designed not only to visit an asteroid and a comet, but to test twelve advanced, high-risk technologies, chief among them the ion propulsion system itself.
Ion propulsion systems generate a tiny amount of thrust. Hold nine quarters in your hand, feel Earth’s gravity pull on them, and you have an idea how little thrust they generate. They can’t be used for launching spacecraft from bodies with strong gravity. Their strength lies in continuing to generate thrust over time. This means that they can achieve very high top speeds. Ion thrusters can propel spacecraft to speeds over 320,000 kp/h (200,000 mph), but they must be in operation for a long time to achieve that speed.
An ion is an atom or a molecule that has either lost or gained an electron, and therefore has an electrical charge. So ionization is the process of giving a charge to an atom or a molecule, by adding or removing electrons. Once charged, an ion will want to move in relation to a magnetic field. That’s at the heart of ion drives. But certain atoms are better suited for this. NASA’s ion drives typically use xenon, an inert gas, because there’s no risk of explosion.
Detail of an ion drive. Image: NASA Glenn Research Center. Vectorization by Chabacano
In an ion drive, the xenon isn’t a fuel. It isn’t combusted, and it has no inherent properties that make it useful as a fuel. The energy source for an ion drive has to come from somewhere else. This source can be electricity from solar cells, or electricity generated from decay heat from a nuclear material.
Ions are created by bombarding the xenon gas with high energy electrons. Once charged, these ions are drawn through a pair of electrostatic grids—called lenses—by their charges, and are expelled out of the chamber, producing thrust. This discharge is called the ion beam, and it is again injected with electrons, to neutralize its charge. Here’s a short video showing how ion drives work:
Unlike a traditional chemical rocket, where its thrust is limited by how much fuel it can carry and burn, the thrust generated by an ion drive is only limited by the strength of its electrical source. The amount of propellant a craft can carry, in this case xenon, is a secondary concern. NASA’s Dawn spacecraft used only 10 ounces of xenon propellant—that’s less than a soda can—for 27 hours of operation.
NASA Evolutionary Xenon Thruster. Image Credit: NASA
In theory, there is no limit to the strength of the electrical source powering the drive, and work is being done to develop even more powerful ion thrusters than we currently have. In 2012, NASA’s Evolutionary Xenon Thruster (NEXT) operated at 7000w for over 43,000 hours, in comparison to the ion drive on DS1 that used only 2100w. NEXT, and designs that will surpass it in the future, will allow spacecraft to go on extended missions to multiple asteroids, comets, the outer planets, and their moons.
Missions using ion propulsion include NASA’s Dawn mission, the Japanese Hayabusa mission to asteroid 25143 Itokawa, and the upcoming ESA missions Bepicolombo, which will head to Mercury in 2017, and LISA Pathfinder, which will study low frequency gravitational waves.
With the constant improvement in ion propulsion systems, this list will only grow.
Dawn's First Glimpse of Vesta – Processed. This image, processed to show the true size of the giant asteroid Vesta, shows Vesta in front of a spectacular background of stars. It was obtained by the framing camera aboard NASA's Dawn spacecraft on May 3, 2011, from a distance of about 1.2 million kilometers (750,000 miles). Since Vesta is so bright that it outshines its starry background, Dawn team members commanded a long exposure time to make the stars visible. They corrected the resulting exaggerated size of Vesta by superimposing a short exposure image of the target asteroid, showing its true size. Vesta is the small, bright pearl in the middle of the image. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
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NASA’s revolutionary Dawn Asteroid Orbiter has begun the final approach phase to the giant asteroid Vesta and snapped its first science image. The image was taken on May 3, when Dawn was approximately 1.21 million kilometers (752,000 miles) distant from Vesta using the science imager known as the Framing Camera.
Besides the pure delight of seeing Vesta up close for the first time, the images play a crucial role in navigating Dawn precisely through space and successfully achieve orbit around the protoplanet that nearly formed into a full fledged planet.
Vesta is the second most massive object in the Asteroid Belt and is 530 kilometers (330 miles) in diameter.
Dawn launch on September 27, 2007 by a Delta II rocket from Cape Canaveral Air Force Station, Florida. Credit: Ken Kremer
Dawn should be captured into orbit about Vesta around July 16 as the engineering team works to maneuver the spacecraft to match the asteroids path around the sun using the exotic ion thrusters. Using the background stars in the framing camera images, they will be able to determine Dawn’s location in space relative to the stars in order to precisely navigate the spacecrafts trajectory towards Vesta.
“After plying the seas of space for more than a billion miles, the Dawn team finally spotted its target,” said Carol Raymond, Dawn’s deputy principal investigator at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “This first image hints of detailed portraits to come from Dawn’s upcoming visit.”
The best images of Vesta to date were taken by the Hubble Space Telescope. Jim Adams, Deputy Director of Planetary Science, told me that the images from Dawn’s Framing Camera will exceed those from Hubble in a few weeks.
Dawn will initially enter a highly elliptical polar orbit around Vesta and start collecting science data in August from an altitude of approximately 1,700 miles (2,700 kilometers). The orbit will be lowered in stages to collect high resolution data as Dawn spends about a year collecting data from its three science instruments.
Dawn's First Glimpse of Vesta -- Unprocessed
This image shows the first, unprocessed image obtained by NASA's Dawn spacecraft of the giant asteroid Vesta in front of a background of stars. It was obtained by Dawn's framing camera on May 3, 2011, from a distance of about 1.2 million kilometers (750,000 miles). Vesta is inside the white glow at the center of the image. The giant asteroid reflects so much sunlight that its size is dramatically exaggerated at this exposure. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Thereafter Dawn will be targeted to Ceres, the largest object in the Asteroid Belt which it will reach in 2015.
Dawn is an international mission.
The framing cameras have been developed and built under the leadership of the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, with significant contributions by the German Aerospace Center (DLR) Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The framing camera project is funded by the Max Planck Society, DLR, and NASA.
The Visible and Infrared mapping camera was provided by the Italian Space Agency. The Gamma Ray Detector was supplied by Los Alamos National Labotatory.
Dawn spacecraft under construction in cleanroom. Picture shows close up view of two science instrument; the twin Framing Cameras at top (white rectangles) and VIR Spectrometer at right. Credit: Ken Kremer
