Wednesday, May 24, 2017

A better ion drive for more efficient space travel

Plasma propulsion – or an ion drive – is common in science fiction, where it can represent a clean, futuristic alternative to the mess and blast of crudely burning rocket fuel. Though it is the most efficient space propulsion method yet devised, it is still rare in reality, where ion drives are weighed down by the bulky engineering currently required to manage the ionised gas propellant.

However, researchers from the University of York in the UK and the École Polytechnique in Paris have taken a major step towards solving the problem.

Existing systems use an electric current to ionize propellant gas and turn it into plasma. The charged ions and electrons are then forced through an exhaust beam, creating thrust.

Current technology – usually in a form known as a gridded-ion thruster – generates more positively charged ions than negative ones. And while that might be useful for moving an object through space, it is also potentially self-defeating.

If the charge imbalance is allowed to remain, the spacecraft would gain a net negative charge, with mission-ending consequences.

In order to deal with this problem, current spacecraft contain an additional piece of kit, called a neutralizer, bolted near the exhaust. The neutralizer generates additional negatively charged ions, balancing the output and ensuring the craft remains electrically neutral.

In 2014 a team at the École Polytechnique demonstrated proof-of-concept for a reconfigured gridded-ion thruster that would produce equal amounts of positive and negative ions without loss of thrust.

The scientists, led by Dmytro Rafalskyi and Ane Aanesland, named the system Neptune and unveiled their findings at an American Institute of Aeronautics and Astronautics conference that year.

Now, the French researchers have teamed up with James Dedrick and Andrew Gibson from the University of York’s Plasma Institute to take the concept to its next stage.

In results published in Physics of Plasmas the scientists report highly detailed observations on how the plasma beam produced by the Neptune system varies in different locations and with varying times and particle strength.

The findings, while still lab-based, take the system a critical step closer to full development.

“The direct observation of how energetic plasma species behave on nanosecond timescales in the Neptune beam will help us to better control the processes that underpin neutralization,” Dedrick says.


Tuesday, May 23, 2017

Trump budget keeps NASA mostly intact but jettisons a few Obama priorities

WASHINGTON – This is no longer Obama’s NASA.

Even though the space agency would get roughly the same $19 billion it received this year, key programs the former president championed – an asteroid mission, several climate change research projects, robust education outreach – would disappear under President Trump’s budget for 2018.

The most high-profile missions remain on target: the continued development of the Space Launch System and Orion vehicle intended to take astronauts to Mars by the 2030s, the launch next year of the James Webb Space Telescope, and the use of private companies to keep delivering cargo and – possibly by the end of 2018 – humans to the International Space Station from American soil.

“What this budget tells us to do is keep going, keep doing what we’ve been doing,” Acting NASA Administrator Robert Lightfoot said Tuesday in a speech to agency employees.

In a $4.1 trillion federal budget proposal that saw some agencies slashed by 10% or more, NASA fared well. The $19.1 billion it would get is about 3% less than the amount Congress appropriated for the current year. And it’s likely lawmakers will make more changes as the budget process unfolds.

It’s unlikely, however that the asteroid mission unveiled under Obama as part of a pathway to Mars will get revived. The Asteroid Redirect Mission, panned roundly by Republican lawmakers, would have corralled a piece of an asteroid and brought it into lunar orbit as a way to test operating systems for deep space exploration.

Instead, NASA officials are looking at deploying a gateway with crew that would serve as a mini space station near the moon to enable trips both to deep space and the lunar surface. The spaceport would be equipped with a small habitat to extend crew time, docking capability, an airlock, and serviced by logistics modules to enable research, according to NASA.

But funding could be an issue, NASA acting Chief Financial Officer Andrew Hunter told reporters Tuesday.

“It’s one area where we are somewhat inhibited by a flat budget,” he said.

The budget also takes aim at climate change research by eliminating five Earth science missions designed to measure a number of global warming factors such as ocean ecosystems and carbon levels. The budget also would cut finding for earth research grants and terminates the Carbon Monitoring System, a project that NASA developed in 2010 in response to congressional direction.

Hunter said NASA’s Earth science component would remain “very robust” at nearly $1.8 billion next year, which he said is more than the average annual budget of the past decade. And Lightfoot pointed out that the budget still includes “significant Earth Science efforts, including 18 Earth observing missions in space as well as airborne missions.”

Read more:

Trump's budget proposal 'savages' climate research, scientists say

NASA won't fly astronauts on first SLS rocket launch

NASA's been busy during Trump's first 100 days

The Trump budget also eliminates the Office of Education, while slashing overall education funding from $100 million this year to $37 million in 2018.

Also included in the proposed budget is:

– $3.9 billion for continued development of the Space Launch System and Orion spacecraft for an eventual crewed mission to the Red Planet within 20 years.

– $2.4 billion for private transportation to the space station. Aerospace firms have been delivering supplies to the orbiting lab since 2012 under the Commercial Cargo program. And NASA is targeting the end of 2018 for the first crewed flight to the space station from U.S. soil.

– $1.9 billion for planetary science, including funding for a 2020 Mars rover mission and a fly-by of Jupiter’s icy moon Europa.

– $1.5 billion for the International Space Station to continue experiments and long-duration human deep space exploration.

– $534 million for the James Webb Space Telescope that is set for an October 2018 launch.

– $624 million for Aeronautics, including development of the Low Boom Flight Demonstrator X-Plane to advance quiet supersonic flight.


Orbit of Earth-Size Exoplanet TRAPPIST-1h in Alien Solar System Nailed Down

The orbits of all seven Earth-size planets in the TRAPPIST-1 system are now known.

Astronomers have nailed down the path of TRAPPIST-1h, the outermost planet in the system, finding that this world takes just under 19 Earth days to complete one lap around its small, faint host star.

The new result suggests that TRAPPIST-1h is too cold to host life as we know it, and it confirms that all seven TRAPPIST-1 worlds circle their star in a sort of gravitational lockstep with one another, study team members said.

"It's incredibly exciting that we're learning more about this planetary system elsewhere, especially about planet h, which we barely had information on until now," Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate at the agency's headquarters in Washington, D.C., said in a statement.

"This finding is a great example of how the scientific community is unleashing the power of complementary data from our different missions to make such fascinating discoveries," Zurbuchen added.

TRAPPIST-1 is a dim, dwarf star just 8 percent as massive as the sun that lies about 40 light-years from Earth. In May 2016, astronomers using the TRAPPIST (Transiting Planets and Planetesimals Small Telescope) instrument in Chile announced the discovery of three roughly Earth-size planets in the system. That number jumped to seven with further observation by NASA's Spitzer Space Telescope, TRAPPIST and other ground-based telescopes.

Three of these seven worlds appear to orbit in TRAPPIST-1's "habitable zone," meaning they might be able to host liquid water, and therefore life as we know it, on their surfaces.

Despite such work, astronomers had not been able to pin down the path of TRAPPIST-1h. But they had noticed that the six other planets in the system are in "orbital resonance." That is, the worlds have tugged each other into stable orbits whose periods are related to each other by a ratio of two small integers.

Similarly, the Jupiter moons Io, Europa and Ganymede are in orbital resonance: For every lap Ganymede completes around Jupiter, Europa makes two orbits and Io completes four. The TRAPPIST-1 resonances are much more complex, but they adhere to the same principle.

The six planets' relationships with each other led the research team to propose six possible resonant orbits for TRAPPIST-1h. Various observations ruled out five of the six, but the sixth was confirmed with observations made by NASA's Kepler space telescope from December 2016 through March of this year, the scientists announced in the new study, which was published Monday (May 22) in the journal Nature Astronomy.

"The resonant structure is no coincidence and points to an interesting dynamical history in which the planets likely migrated inward in lockstep," lead author Rodrigo Luger, a doctoral student at the University of Washington in Seattle, said in the same statement. "This makes the system a great test bed for planet-formation and -migration theories."

TRAPPIST-1 holds the record for most planets found in orbital resonance. Second place is a tie between the exoplanetary systems Kepler-80 and Kepler-223, each of which is known to harbor four resonant worlds.

TRAPPIST-1h receives about the same amount of energy from its star as the dwarf planet Ceres, the largest object in the main asteroid belt between Mars and Jupiter, gets from Earth's sun, NASA officials said. So TRAPPIST-1h is most likely a frigid world unable to host Earth-like life, they added.

But that may not always have been the case. The star TRAPPIST-1 is thought to be between 3 billion and 8 billion years old. It was likely much brighter in its youth, perhaps bright enough to make TRAPPIST-1 habitable for several hundred million years in the ancient past, Luger said.


Wednesday, May 10, 2017

Given the hazards of landing on Mars, SpaceX may send two Dragons in 2020

Elon Musk has spoken favorably about NASA's Mars Exploration Rover missions.

In recent months, SpaceX has acknowledged that it will not be able to launch an uncrewed Dragon spacecraft to Mars in 2018. The technology to send the capsule safely through deep space and propulsively land it on Mars just won't be ready. However, that delay opens up an opportunity to launch two Dragons in 2020. And that's what SpaceX appears likely to do.

NASA's manager of science missions, Jim Green, said on Tuesday that the 2020 launch window when Earth and Mars are in favorable alignment for relatively short transits is getting crowded. Speaking Tuesday at the Humans to Mars conference in Washington, DC, Green said, "Every 26 months, the highway to Mars opens up, and that highway is going to be packed. We start out at the top of that opportunity with a SpaceX launch of Red Dragon. That will be followed at the end of that opportunity with another Red Dragon. Those have been announced by SpaceX." NASA plans to launch a Mars lander in 2020 as well.

Two Red Dragon missions in 2020 have not yet formally been announced by SpaceX. Company spokesman John Taylor told Ars he would have to look into the question of sending two Dragons to Mars in 2020. However, other industry sources told Ars this is definitely under consideration by SpaceX, although no final decisions have been made.

Propulsive landing

In the past, SpaceX founder Elon Musk has spoken favorably about NASA's Mars Exploration Rover missions, Spirit and Opportunity, which landed four weeks apart in 2004 on Mars. The essential idea for Musk is to hedge his bets with two landings and potentially to learn from the first attempt to use experimental supersonic retropropulsion in the thin Martian atmosphere to slow the vehicle's descent.

Successfully landing a Dragon on Mars would be unprecedented. The spacecraft would likely enter the Martian atmosphere weighing about eight tons, and it would burn two of those tons as propellant to get down to the surface. Compare that to the largest object humans have ever landed on Mars, the Curiosity rover. Curiosity started off at 3.6 tons before entering the atmosphere, and through its sky crane and other steps, it shed weight down to 900kg by the time it reached the surface. Propulsive landing is key to eventual human missions to the red planet for one simple reason—it scales up to about 30 tons.

SpaceX hasn't talked openly about payloads on the Mars landers, but it's likely that the company will include some NASA instruments or experiments, and it may also issue an open call to universities for ideas. It's expected that any payloads will be related to technology and science needed to further human exploration of the red planet, which remains SpaceX's long-term goal.


Buzz Aldrin to NASA: Retire the International Space Station ASAP to Reach Mars

If NASA and its partner agencies are serious about putting boots on Mars in the near future, they should pull the plug on the International Space Station (ISS) at the earliest opportunity, Buzz Aldrin said.

"We must retire the ISS as soon as possible," the former Apollo 11 moonwalker said Tuesday (May 9) during a presentation at the 2017 Humans to Mars conference in Washington, D.C. "We simply cannot afford $3.5 billion a year of that cost."

Instead, Aldrin said, NASA should continue to hand over activities in low Earth orbit (LEO) to private industry partners. Indeed, the space agency has been encouraging that move by awarding contracts to companies such as SpaceX, Orbital ATK and Boeing to ferry cargo and crew to and from the ISS.

Bigelow Aerospace, Axiom Space or other companies should build and operate LEO space stations that are independent of the ISS, he added. Ideally, the first of these commercial outposts would share key orbital parameters with the station that China plans to have up and running by the early 2020s, to encourage cooperation with the Chinese, Aldrin said.

Establishing private outposts in LEO is just the first step in Aldrin's plan for Mars colonization, which depends heavily on "cyclers" — spacecraft that move continuously between two cosmic destinations, efficiently delivering people and cargo back and forth.

"The foundation of human transportation is the cycler," the 87-year-old former astronaut said. "Very rugged, so it'll last 30 years or so; no external moving parts."

Step two involves the international spaceflight community coming together to build cyclers that ply cislunar space, taking people on trips to the moon and back. Such spacecraft, and the activities they enable, would allow the construction of a crewed lunar base, where humanity could learn and test the techniques required for Mars colonization, such as how to manufacture propellant from local resources, Aldrin said.

Then would come Earth-Mars cyclers, which Aldrin described as "an evolutionary development" of the prior cyclers.

Aldrin foresees these various cycler iterations enabling a crewed mission to a near-Earth asteroid by 2020 and a Venus flyby by 2024. If all goes well, the first future Mars settlers could launch in the early 2030s, he said.

And they will be settlers, not just visitors, if Aldrin's vision comes to pass.

"Let's be certain that we've developed a sustainable plan to stay on Mars," he said. "No flags and footprints this time."

The ISS is currently funded through 2024, and officials of NASA, the Russian federal space agency and other partners have floated the possibility of extending the $100 billion outpost's life through 2028. NASA officials have repeatedly said that the ISS is a key part of the agency's "Journey to Mars" vision, which aims to get astronauts to the vicinity of the Red Planet sometime in the 2030s.

NASA's Mars Plan May Include Yearlong Mission to the Moon

A group of astronauts may spend a year in orbit around the moon in the late 2020s as part of NASA's plan to send humans to Mars in the 2030s, agency officials said today (May 9).

Greg Williams, NASA's deputy associate administrator for policy and plans in the agency's Human Exploration and Operations Mission Directorate, spoke today at the Humans to Mars Summit in Washington D.C. and provided a detailed look at the first two phases of NASA's current plan to send humans to Mars.

The agency recently announced that its Mars plan now includes building a "deep-space gateway" around the moon to serve as a testing ground for operations and technology that will be required for those Red Planet missions, Williams said. Eventually, the lunar presence would also serve as a launching point for the spacecraft that will carry humans to Mars, he added. The yearlong crewed mission around the moon in 2027 is one of the major future milestones of the current plan.

Before that yearlong lunar mission, however, there would be at least five missions, four of them crewed, to deliver hardware, such as a crew habitat, Williams said during his presentation. The last piece of delivered hardware would be the actual Deep Space Transport vehicle that would later be used to carry a crew to Mars, he said.

"If we could conduct a yearlong crewed mission on this Deep Space Transport in cislunar space, we believe we will know enough that we could then send this thing, crewed, on a 1,000-day mission to the Mars system and back," Williams said. 

Inside NASA, the yearlong mission was being casually referred to as a "shakedown cruise," which is a term used in the Navy to describe a trip intended to test the performance of a new ship, Williams said. But the team decided to change the terminology because, "if you have a Sicilian mafia background, ['shakedown'] has a different connotation," he said, referring to the illegal practice of extorting money from small businesses, generating laughter from the audience. "So we're still wrestling with how we want to describe this thing."  

A plan to get to Mars

Currently, the lunar stages of the plan to get humans to Mars rely heavily on NASA's Space Launch System (SLS) rocket to send the necessary payloads and crews to cislunar space. (Cislunar refers to the region between Earth and the moon, including orbits around the moon itself. Williams said NASA would like to see some of its vehicles not only occupy a single orbit around the moon, but make trips to various locations in cislunar space.) The date of the first SLS flight is yet to be determined as the agency discusses the possibility of including a crew on that maiden voyage. The rocket would carry crews in the agency's Orion space capsule, which has made one uncrewed test flight.

Williams focused mainly on the first two phases of NASA's humans to Mars plan, which will establish the deep-space gateway. Phase 1 is scheduled to be carried out between 2018 and 2026, and would include four crewed flights to cislunar space to deliver four key pieces of infrastructure: a power and propulsion bus, a crew habitat, a logistics module (for science research) and an airlock for other visiting vehicles. Williams said the facility would also include a robotic arm that could help provide the module with more autonomous functions. (Details about the current timeline, and many of the slides Williams used in his talk, can be found here.)

Phase 2, which would begin in 2027, would start with an uncrewed mission to deliver the Deep Space Transport vehicle to cislunar space, followed by a flight to deliver the one-year crew to thefacility. In the late 2020s, there would be more flights to deliver the supplies necessary for the first human flights to the Mars system in the 2030s. 

This plan is "evolving," Williams noted, and it will likely change as NASA establishes collaborations with industry partners and other nations to support the long-term mission. 

"We're trying to lead this journey to Mars with a broad range of partnerships," Williams said. "One of the things we'll be doing over the next few years is, putting that package together: what players want to provide what — both nationally and internationally — and how we can together, with NASA in an orchestrating role, really move out on these crewed missions to Mars."

Friday, May 5, 2017

NASA’s James Webb Space Telescope completes testing at Goddard

NASA’s James Webb Space Telescope (JWST) successfully completed the center of curvature test, a crucial optical measurement of the telescope’s primary mirror prior to cryogenic testing, and the final test at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

The spacecraft will be shipped to NASA’s Johnson Space Center in Houston for more testing.

“The Webb telescope is about to embark on its next step in reaching the stars as it has successfully completed its integration and testing at Goddard,” said Bill Ochs, NASA’s Web telescope project manager. “It has taken a tremendous team of talented individuals to get to this point from all across NASA, our industry and international partners, and academia. It is also a sad time as we say goodbye to the Webb Telescope at Goddard, but are excited to begin cryogenic testing at Johnson.”

JWST will experience high levels of noise and vibration during the rocket launch that will carry into space. Engineers at Goddard tested the space telescope in vibration and acoustics test facilities that simulate the launch environment to ensure that functionality is not impaired by the stresses of a rocket ride into space.

Optical engineers set up an interferometer, the main device used to measure the shape of the telescope’s mirror, both before and after the environmental tests. An interferometer records and measures the ripple patterns that result when different beams of light mix and their waves combine or “interfere.”

Waves of visible light are less than a thousandth of a millimeter long. The optics on JWST must be shaped and aligned even more accurately than that to function properly.

Using lasers to measure the mirror’s shape prevents physical contact that could scratch the mirror. By measuring light reflected off of the optics using an interfererometer, scientists are able measure extremely small changes in shape or position that may occur after exposing the mirror to a simulated launch or temperatures that simulating the subfreezing environment of space.

Temperature and humidity conditions in the clean room were kept incredibly stable during testing to minimize fluctuations in the optics over time. To compensate for the tiny vibrations that remained, the interferometer is a “high-speed” one that takes 5,000 frames per second, a faster rate than the vibrations themselves. This allows engineers to subtract out vibrations and get clean results of any change in the mirror’s shape.

“Some people thought it would not be possible to measure beryllium mirrors of this size and complexity in a clean room to these levels, but the team was incredibly ingenious in how they performed these measurements and the results give us great confidence we have a fantastic primary mirror,” said Lee Feinberg, Webb’s telescope optical element manager.

The JWST will be shipped to Johnson Space Center for optical testing in a vacuum at extremely cold temperatures. Then the spacecraft will go to Northrop Grumman Aerospace Systems in Redondo Beach, California, for final assembly and testing before launch in 2018.