Monday, August 14, 2017

NASA contracts energy firm to refine nuclear thermal propulsion concepts

As the U.S. government continues to pursue plans for a crewed mission to Mars, NASA has contracted with BWXT Nuclear Energy Inc. of Lynchburg, Virginia, to advance concepts in Nuclear Thermal Propulsion (NTP), which could drastically reduce travel times to Mars.

This is part of NASA’s Game Changing Development Program, which takes ideas from academia and industry as well as NASA and other government programs, to advance new approaches to space technologies to accommodate the changing needs of U.S. space efforts.

NTP is not a new concept, but it was abandoned in 1972 when plans for a Mars mission were shelved. NASA conducted ground tests since 1955 to determine the viability of NTP and has occasionally been revisited as a conceptual part of Mars mission feasibility studies.

The advantage of NTP is mainly in that it can provide twice the rocket thrust of the Space Shuttle Main Engines (SSMEs), which are among the most powerful chemical rockets ever developed.

Sonny Mitchell, Nuclear Thermal Propulsion project manager at Marshall, said: “As we push out into the Solar System, nuclear propulsion may offer the only truly viable technology option to extend human reach to the surface of Mars and to worlds beyond. We’re excited to be working on technologies that could open up deep space for human exploration.”

Rex Geveden, BWX Technologies’ president and CEO, said: “We are uniquely qualified to design, develop and manufacture the reactor and fuel for a nuclear-powered spacecraft. This is an opportune time to pivot our capabilities into the space market where we see long-term growth opportunities in nuclear propulsion and nuclear surface power.”

Using conventional rockets, a mission to Mars at opposition would take six months. NTP could cut the travel time to four months. There are several advantages to cutting down travel time. One is that the astronauts would get less exposure to solar radiation – something that is of greater concern, as some recent studies suggest that the Apollo lunar astronauts may have had their health more adversely affected by radiation during their journeys than previously realized.

A shorter travel time will also reduce the vehicle’s mass. It would need to carry less fuel and fewer consumables – and could, therefore, carry more payload.

It works by expanding a propellant, such as hydrogen, by heating it in a nuclear reactor. This differs from chemical rockets, in which the fuel is the heat source. As a result, an NTR rocket can use a propellant with a low molecular weight rather than complex fuels such as kerosene or hydrazine.


Friday, August 11, 2017

NASA's New Plasma Rocket Ready For Testing

Most of today's rockets are chemical rockets, which means they propel themselves through space by combining certain chemicals in a way that makes them explosive. Chemical rockets are heavy and fast-burning, which is great for getting off the surface of Earth, but less great for long voyages to the outer solar system.

For these longer trips, NASA is looking at using a new type of rocket: the plasma rocket.

NASA awarded a contract to the company Ad Astra back in 2015 to build a plasma rocket, and that rocket is rapidly approaching readiness. The company has been running several short tests of the engine and is preparing for a longer, 100-hour test. Once that happens sometime next year, the rocket engine will be closer to real missions.

The plasma rocket, the Variable Specific Impulse Magnetoplasma Rocket (VASIMR), works by heating neon or argon gas to incredibly high temperatures using magnetic fields. That hot plasma is then fired out of the back of the rocket at very high speeds, providing thrust.

The plasma rocket has an advantage over traditional chemical propellants in that it can provide a small amount of thrust over a very long time, such as days, weeks, or months. Longer burn times mean the rocket needs less fuel, and less fuel means the rocket can carry more cargo. Of course, longer burn times also means longer travel times, but when you're just ferrying around supplies a few extra weeks or months isn't too important.

In addition to carrying cargo, plasma rockets could be used to send spacecraft to distant targets more quickly. Plasma rockets could enable us to reach Jupiter, Saturn, or more distant targets in a year or two instead of the better part of a decade, which could mean more missions to the outer solar system.

In a few short years, plasma might be propelling us around the solar system.


Wednesday, August 9, 2017

Four Earth-sized planets detected orbiting the nearest sun-like star

A new study by an international team of astronomers reveals that four Earth-sized planets orbit the nearest sun-like star, tau Ceti, which is about 12 light years away and visible to the naked eye. These planets have masses as low as 1.7 Earth mass, making them among the smallest planets ever detected around nearby sun-like stars. Two of them are super-Earths located in the habitable zone of the star, meaning they could support liquid surface water.

The planets were detected by observing the wobbles in the movement of tau Ceti. This required techniques sensitive enough to detect variations in the movement of the star as small as 30 centimeters per second.

"We are now finally crossing a threshold where, through very sophisticated modeling of large combined data sets from multiple independent observers, we can disentangle the noise due to stellar surface activity from the very tiny signals generated by the gravitational tugs from Earth-sized orbiting planets," said coauthor Steven Vogt, professor of astronomy and astrophysics at UC Santa Cruz.

According to lead author Fabo Feng of the University of Hertfordshire, UK, the researchers are getting tantalizingly close to the 10-centimeter-per-second limit required for detecting Earth analogs. "Our detection of such weak wobbles is a milestone in the search for Earth analogs and the understanding of the Earth's habitability through comparison with these analogs," Feng said. "We have introduced new methods to remove the noise in the data in order to reveal the weak planetary signals."

The outer two planets around tau Ceti are likely to be candidate habitable worlds, although a massive debris disc around the star probably reduces their habitability due to intensive bombardment by asteroids and comets.

The same team also investigated tau Ceti four years ago in 2013, when coauthor Mikko Tuomi of the University of Hertfordshire led an effort in developing data analysis techniques and using the star as a benchmark case. "We came up with an ingenious way of telling the difference between signals caused by planets and those caused by star's activity. We realized that we could see how star's activity differed at different wavelengths and use that information to separate this activity from signals of planets," Tuomi said.

The researchers painstakingly improved the sensitivity of their techniques and were able to rule out two of the signals the team had identified in 2013 as planets. "But no matter how we look at the star, there seem to be at least four rocky planets orbiting it," Tuomi said. "We are slowly learning to tell the difference between wobbles caused by planets and those caused by stellar active surface. This enabled us to essentially verify the existence of the two outer, potentially habitable planets in the system."

Sun-like stars are thought to be the best targets in the search for habitable Earth-like planets due to their similarity to the sun. Unlike more common smaller stars, such as the red dwarf stars Proxima Centauri and Trappist-1, they are not so faint that planets would be tidally locked, showing the same side to the star at all times. Tau Ceti is very similar to the sun in its size and brightness, and both stars host multi-planet systems.

A paper on the new findings was accepted for publication in the Astrophysical Journal and is available online.


Friday, July 28, 2017

SpaceX schedules Falcon Heavy's maiden launch for November

Elon Musk warns that it might not reach orbit, though.

SpaceX chief Elon Musk has revealed that the company is sending its heavy lift rocket to space for the first time in November. The company was originally gunning for a summer launch, but in June, the CEO told a Twitter follower that Falcon Heavy's cores will take two to three months to reach Cape Canaveral. SpaceX will need a bit of time after they arrive to prepare the rocket.

Falcon Heavy is powered by three Falcon 9 cores, which gives it thrice the payload capacity of the smaller launch vehicle. Earlier this year, the private space corporation was thinking of trying to reland and recover its upper stage during its maiden flight. That seems off the table now, though -- in fact, Musk set expectations pretty low for the launch. At a space conference in Washington last week, he said there's a good chance that Falcon Heavy won't even reach orbit the first time it leaves the atmosphere.

The rocket will take off from NASA's historic launch pad 39A at the Kennedy Space Center, but the company hasn't decided on the exact date and time yet. It'll likely announce those details in the next few months, as well as confirm whether it will stream the event online.


After Delays, SpaceX and Boeing Aim to Launch Astronauts Next Year

The race is on between the Dragon 2 and the Starliner.

Back in 2014, SpaceX and Boeing both received contracts under NASA's Commercial Crew Development program to build spacecraft that could carry astronauts to the International Space Station. The program is intended to allow NASA to launch astronauts on American spacecraft again, something that hasn't happened since the last flight of the space shuttle in 2011.

The spacecraft being developed by SpaceX and Boeing—the Dragon 2 and the CST-100 Starliner, respectively—proved to be more difficult than originally anticipated. Both companies pushed back their plans for 2017 flights to 2018. Elon Musk recently said the Crew Dragon, which is what NASA calls the Dragon 2, is "way more difficult" than the cargo version of the spacecraft that is used to take supplies to the ISS. "As soon as people enter the picture, it's really a giant step up in making sure things go right," said Musk at a recent panel on the commercial crew program. "The oversight from NASA is much tougher."

Fortunately, however, the work to achieve flights next year seems to be progressing nicely. NASA along with Boeing and SpaceX have indicated that they are on track to hit target launch dates in 2018. A July 20 report released by NASA shows that SpaceX is still targeting an unmanned test flight in February 2018 and a crewed flight in June 2018, and Boeing is aiming to launch an unmanned test flight in June 2018 and a crewed flight in August 2018. Boeing also plans to conduct pad abort tests in early 2018.

Future delays are certainly possible, and Boeing's director of the Starliner program, Chris Ferguson, called the timeline "a very aggressive test program," as reported by Space News. Still, Ferguson said it's possible that the first real mission to take astronauts to the ISS on the Starliner could launch as soon as December 2018. After that, there will not be another change in personnel aboard the space station until around May 2019.

SpaceX plans to launch its Dragon 2 on an upgraded version of the Falcon 9 rocket known as Block 5, currently in development. The Block 5 iteration of the Falcon 9 should produce more thrust in all engines and have reinforced landing legs. Boeing plans to launch the Starliner on an Atlas V rocket supplied by United Launch Alliance (ULA), a joint venture between Boeing and Lockheed Martin.

While SpaceX tends to keep everything close to the chest, there are a few future announcements from Boeing that could indicate progress in its commercial crew program. First of all, ULA will want a preliminary agreement about a launch about a year in advance, so it's possible we hear something from ULA about the first test flight of the Starliner sooner rather than later.

Also, the crewed test flight of the the Starliner will include a NASA astronaut and a Boeing test pilot. When NASA announces the astronaut for that flight, it will be a strong indication that the the agency is confident the launch is on track. "Once when they feel comfortable that they're about 12 months out from a crewed flight launch, I think you can see an assignment come out," said Ferguson.

SpaceX and Boeing have hit a few snags in their quest to build human-rated spacecraft, but their labors are finally coming together. Come 2018, Americans could fly on American spaceships once again.

Thursday, July 20, 2017

SpaceX drops plans for powered Dragon landings

WASHINGTON — SpaceX no longer plans to have the next version of its Dragon spacecraft be capable of powered landings, a move that has implications for the company’s long-term Mars plans.

SpaceX Chief Executive Elon Musk, speaking at the International Space Station Research and Development Conference here July 19, confirmed recent rumors that the version of the Dragon spacecraft under development for NASA’s commercial crew program will not have the ability to land on land using SuperDraco thrusters that will be incorporated into the spacecraft primarily as a launch abort system.

“It was a tough decision,” he said when asked about propulsive landing capability during a question-and-answer session. “Technically it still is, although you’d have to land it on some pretty soft landing pad because we’ve deleted the little legs that pop out of the heat shield.”

SpaceX planned to transition from splashdowns, which is how the current cargo version of the Dragon returns to Earth, to “propulsive” landings at a pad at some point after the vehicle’s introduction. Certification issues, he said, for propulsive landings led him to cancel those plans.

“It would have taken a tremendous amount of effort to qualify that for safety, particularly for crew transport,” he said.

Another reason for the change, he said, is that SpaceX had reconsidered what is the best way to land large spacecraft on the surface of Mars in support of the company’s long-term goals to establish a human presence there.

“There was a time that I thought the Dragon approach to landing Mars, where you’ve got a base heat shield and side-mounted thrusters, would be the right way to land on Mars,” he said. “Now I’m pretty confident that is not the right way and there’s a far better approach.”

He didn’t describe that alternative approach, but said that “the next generation of SpaceX rockets and spacecraft” will use that different landing technique. In a later tweet, though, Musk clarified that the alternative approach will also use a version of propulsive landing.

“It doesn’t seem like the right way of applying resources right now,” he said of the original propulsive landing technique.

Abandoning that propulsion landing technique would also appear to put into jeopardy SpaceX’s planned Red Dragon spacecraft, which would have landed a Dragon 2 spacecraft on the Martian surface. SpaceX announced plans for Red Dragon last year for launch in 2018, but SpaceX President Gwynne Shotwell said in February that the launch had slipped to 2020 as the company focused on its commercial crew program and a return to flight of the Falcon 9 after a September 2016 pad explosion.

More recently, there were rumors that SpaceX had either further delayed that first Red Dragon mission or cancelled it entirely. Musk did not directly address the status of Red Dragon in his talk, but the lack of propulsion landing systems, particularly legs, would appear to rule out such missions.

Musk also confirmed in the interview that SpaceX is developing a revised version of the overall Mars exploration architecture that he unveiled at the International Astronautical Congress (IAC) in Guadalajara, Mexico, in September 2016. That plan involved the development of giant reusable launch vehicles, called the Interplanetary Transport System, for sending spacecraft to the surface of Mars or elsewhere in the solar system.

“It’s evolved quite a bit since the last talk,” Musk said of the Mars architecture. “The key thing that I’ve figured out is how to pay for this whole system to go to Mars. It’s super expensive.”

That alternative approach, he said, involves decreasing the size of the vehicles somewhat. “You make it capable of doing Earth orbit activity as well as Mars activity,” he said. “Maybe we can pay for it by using it for Earth orbit activity. That’s one of the key elements of the new architecture.”

“I think this one’s got a shot of being real on the economic front,” he said. That update, he said, may be presented at this year’s IAC in September in Adelaide, Australia.

Falcon Heavy and commercial crew

In the near term, though, Musk said SpaceX is primarily focused on completing development of the crewed version of the Dragon spacecraft. “Overall I think it’s going really well,” he said, with plans in place to start test flights of the vehicle around the middle of 2018.

That timeline is well behind the original schedule for the program, which called for the vehicle to be certified by NASA by the end of 2017. “It’s been way more difficult than cargo, to be sure,” he said of commercial crew development. “As soon as people enter the picture, it’s really giant step up in making sure things go right.”

Musk said NASA oversight was “much tougher” than on the commercial cargo program, but that disagreements were limited to “small technical bones of contention” with the agency. He didn’t given examples of those issues, beyond calling them “esoteric.”

“Overall, I’m confident that it’s going to be a system that NASA feels good about and SpaceX feels good about,” he said.

Also coming up is the first flight of the long-delayed Falcon Heavy rocket, now planned for late this year. Musk repeated earlier comments that development of the rocket, years behind schedule, was much more difficult than originally anticipated.

Musk also appeared to lower expectations about the success of that first launch. He said that liftoff requires the simultaneous ignition of 27 engines: nine engines in each of the three booster cores. “There’s a lot that could go wrong there,” he said, also citing the dynamical environment of the Falcon Heavy in flight that is difficult to test on the ground.

“There’s a lot of risk associated with the Falcon Heavy,” he said. “There’s a real good chance that vehicle does not make it to orbit. I want to make sure and set expectations accordingly.”

“I encourage people to come down to the Cape to see the first Falcon Heavy mission,” Musk said. “It’s guaranteed to be exciting.”


SpaceX's Big New Rocket May Crash on 1st Flight, Elon Musk Says

There's a "real good chance" the vehicle won't make it to orbit during the liftoff, Musk said Wednesday (July 19) at the 2017 International Space Station Research and Development (ISSR&D) conference in Washington, D.C. That launch is expected to take place later this year from Florida's Space Coast.

"I hope it makes it far enough away from the pad that it does not cause pad damage. I would consider even that a win, to be honest," Musk told NASA ISS program manager Kirk Shireman, who interviewed the SpaceX CEO onstage at the meeting. "Major pucker factor, really; that's, like, the only way to describe it."

The two-stage Falcon Heavy is based on SpaceX's Falcon 9 rocket, which has been ferrying payloads to space since 2010. The Heavy's first stage consists of two Falcon 9 first stages strapped to a central "core," which is itself a modified Falcon 9 booster.

Like the Falcon 9, the Heavy is designed to be reusable.

When the 230-foot-tall (70 meters) Falcon Heavy is up and running, it will be capable of lofting up to 60 tons (54 metric tons) to low-Earth orbit and 24 tons (22 metric tons) to geostationary transfer orbit, making it the most powerful rocket since NASA's famous Apollo-era Saturn V launcher, SpaceX representatives have said.

SpaceX has been developing the Falcon Heavy for years. The work has proven to be "way, way more difficult" than SpaceX originally expected, Musk said.

"At first, it sounds really easy: Just stick two first stages on as strap-on boosters. How hard can that be?" he said. "But then everything changes. All the loads change, aerodynamics totally change, you've tripled the vibration and acoustics."

The loads imparted on the center core during Falcon Heavy launches will be "crazy," Musk said, "so we had to redesign the whole center-core airframe. It's not like the Falcon 9, because it's got to take so much load."

In addition, it's impossible to fully test many aspects of the vehicle on the ground, he said.

So, while Musk stressed that he thinks the Falcon Heavy will prove to be "a great vehicle," the initial liftoff could be rocky.

"I encourage people to come down to the cape to see the first Falcon Heavy mission," he said, referring to Florida's Cape Canaveral. "It's guaranteed to be exciting."

SpaceX has not yet announced an official date for the launch. Musk recently suggested on Twitter, however, that the liftoff may happen in September or October.