May 13, 2013
Somebody had to do it.
Commander Chris Hadfield returns to Earth this evening, along with Expedition 34/35 crewmates Dr. (not Major) Tom Marshburn and Roman Romanenko. NASA TV coverage of their departure from the International Space Station begins at 3:30.
December 3, 2012
The first humans that head out to Mars might never set foot on the planet. Instead, they could orbit on a Martian space station, where the astronauts remotely command robots working on the planet’s harsh surface. Operating from an orbiting platform — one that’s already set up to support humans, because they flew to Mars inside it — would give the astronauts a wide field of view; they could send robots almost anywhere on the planet and change course as needed, without having to find the kind of safe route that people would require. Indeed, these robots would find it for us.
Astronauts are starting to test these techniques now, except instead of operating robots from low-Mars orbit, they’re driving Lego rovers in Germany from the International Space Station. In late October, then-station commander Sunita Williams opened a laptop and sent the terrestrial toy through a short obstacle course. The tricky part is not the remote operation itself, though it requires some training (no doubt the Mars Curiosity drivers could offer some tips), it’s the infrastructure needed to transmit the signal: the interplanetary Internet.
“The history of space communications is largely what we call point-to-point — we point a big antenna on Earth up at a spacecraft, squirt commands up to it, and we get telemetry back,” explains Adrian Hooke, NASA’s project manager for Space DTN (Disruption Tolerant Networking). He adds that the Mars Curiosity rover is a step ahead of this, using two Mars orbiters as communication relays. “But what we want is a more Internet-like system… of pretty ubiquitous communications, anywhere you want to go.”
You’re reading this blog post thanks to a nearly 40-year-old technology called Internet Protocol (IP). Information travels in packets, hopping from router to router, but if a router has nowhere to send the data because the next router is down, it simply discards those packets.
DTN, however, aims to be a more careful, and thus more reliable system. When mission control on Earth is waiting for a commander’s update from Mars, or when astronauts are carefully constructing our first Martian base from 200 miles up, they don’t want to risk losing any of that data forever if a router burps. So DTN uses Bundle Protocol (BP) — the IP of the interplanetary Internet. Here, when a router receives data packets, it stores them until the next hop becomes available. If the delays are large — due to the vast distances between planets, or because a Mars orbiter is on the far side of the planet — DTN can use a secondary system, called Licklider Transmission Protocol (LTP), which will store the data even if the sender has to go offline before the transmission is complete.
When Williams instructed the Lego rover in Germany to move, the command went from her laptop to the space station’s communications terminal, where a DTN access point began, operated by the University of Colorado. Then it went to NASA’s fleet of tracking and relay satellites, which transmitted the data packets to ground stations in White Sands, New Mexico, then to NASA’s operations center in Huntsville, Alabama, and on to the University of Colorado in Boulder, where they hopped the pond to the European Space Agency’s user support center in Belgium, and finally to ESA’s operations center in Darmstadt, Germany. Then the Lego rover moved. Measurements confirming the movement then traveled the reverse route back to Williams.
“Each one of those was a DTN ‘hop,’” Hooke says. “Sunita steered the robot around some obstacles, and got some very basic data back from the rover…given all those hops, it probably took a couple seconds round trip. She probably saw the response three seconds after she sent the commands.”
For this test, NASA’s DTN team worked with ESA’s METERON project, Multi-purpose End-To-End Robotic Operations Network, which is focused on developing astronaut “telepresence” — operating robots remotely. The ESA hopes that in the coming year or so, astronauts will be tele-operating “Justin,” an android, from the space station.
Eventually, the DTN developed for space could be used by regular folks here on Earth in times of emergency, when communication links are disrupted or jammed, such as during a hurricane or terrorist attack. But NASA’s sights are set far from home. Hooke says interplanetary probes like the Saturn-orbiting Cassini and the upcoming Juno mission to Jupiter, could be repurposed by uploading them with DTN software after their science missions are done. That way, they can serve as Internet nodes throughout the solar system.
“There is nothing inherent in the network that can constrain how far out you can go. It’s more [constrained by] the patience of human beings to wait for a response,” he says.
November 8, 2012
Thirty-five new occupants arrived at the International Space Station in late October. Three were astronauts, the rest were fish.
“This is the first experiment in the world to take care of animals for such a long time in the space station — for two months,” says Akira Kudo of the Tokyo Institute of Technology. “Normally, animals are cared for for just two weeks. Only astronauts stay longer than that.”
Kudo is the principal investigator for a study called Medaka Osteoclast, or MOST, examining how the bones of the medaka fish — also known as Japanese killifish, which are popular both as pets and research animals — will respond to microgravity. (Medaka fish were the first vertebrates to mate in space; four of them successfully laid and hatched eggs in an experiment aboard Columbia in 1994.)
The fish are living in a specially designed space aquarium called the Aquatic Habitat, partitioned into two, 1.5-pint sections. Housed in the Japanese Kibo module, the habitat has temperature control, water circulation and bacterial filtration systems, and an oxygen supply from a modified artificial lung machine. It also has an automatic feeder — no fish flakes floating around. Like diligent home aquarists, astronauts have to test and clean the water twice a week for the first three weeks, then three times every 14 days after that.
Japanese astronaut Aki Hoshide started the experiment by sacrificing and preserving eight of the fish in a stabilizing solution as controls, and moving 16 more from the transport unit into the Habitat. Today, after two weeks of swimming in microgravity, Hoshide removed six more medakas and preserved them in a type of formaldehyde; they’ll return with the astronauts next week on the Soyuz. Other station crew members will care for the remaining 10 fish, preserve them after 60 days, and send them back to Earth on a SpaceX Dragon capsule. Kudo plans to dissect them in ultra-thin slices to examine their bone densities.
His main goal is to understand the formation of osteoclasts, cells that absorb bone, and how microgravity affects the interaction between these and osteoblasts, bone-forming cells. Scientists already know that bone density decreases in space, and Kudo suspects it has to do with increased osteoclast production.
Medaka fish are particularly useful for this study because they’re transparent, which allows easy viewing of their bones and organs. They are also easy to modify genetically: those aboard the station have fluorescent proteins that cause osteoclasts to glow green and osteoblasts to glow red. (How nice that they’ll be aboard for Christmas!)
The aquarium also is set up for observation. Astronauts and scientists on the ground are able to watch the fish swim in loops, rather than in straight lines, because there’s no sense of up or down to orient them. The medaka are rapid breeders, so there’s a strong possibility for fish fry (fish babies, that is, not a dinner buffet) in space, up to three generations in the time they’ll be aboard — that would be a first for space fish. Further experiments will study organ formation, and the aquarium is also designed to house frogs.
At JAXA’s Tsukuba Space Center, Kudo can watch a live video feed to check whether the fish are swimming and eating normally. The medaka are already of great interest to the six space astronauts, who can look in on the fish as they go about their work. Kudo says: “We call them fishonauts.”
November 2, 2012
In space, a drop of fuel burns in a sphere, symmetrically sucking in oxygen and producing heat and gas equally on all sides. With no gravity to make hot gas rise, flames lack the teardrop shape they assume on Earth. “It’s a ball of fire, more or less,” explains Forman Williams, a combustion researcher at the University of California, San Diego.
Williams is the principal investigator for Flame Extinguishment Experiment 2, or FLEX-2, which studies these fireballs on board the International Space Station. Williams hopes his experiment will provide insight into the basic physics and chemistry of combustion, and lead to improved fire safety in space.
FLEX-2 takes place in the 560-pound Combustion Integrated Rack, which is located in the station’s Destiny lab module. Inside the rack, an apparatus about the size of a bread box can be filled with different mixtures of oxygen, nitrogen and helium gas. Tiny droplets of fuel, like methanol or heptane, are dispensed into the combustion zone through a syringe. “Since there is no gravity, the droplet just sits there,” Williams says. The droplets are ignited and can burn for up to 20 seconds or so (the exact time depends on the gas and fuel), shrinking as the fuel is consumed. While one camera records the droplet size, radiometers and an ultraviolet camera record the flame radiation, and another visible-light camera records the droplet and the flame.
Last summer, astronauts completed multiple rounds of experiments, typically doing four to 10 droplet burns in a session, twice a week. The first FLEX experiment studied the physics of flame extinction — how flames die out when there’s not enough fuel or oxygen — and was geared toward spacecraft safety. FLEX-2 is “more science-oriented,” says Williams, and is investigating fuel mixtures that might be used in high-efficiency automobile engines.
In the video above, a suspended droplet of heptane burns for a couple of seconds in a “hot flame,” then — when the scene appears mostly dark — burns in a “cool flame,” a steady, lower-temperature combustion. Finally, the droplet extinguishes in a bright orange vapor cloud.
The team has already made one interesting observation. “We were burning these heptane droplets out there on station, and we saw the hot flame extinguish, but the droplet kept decreasing in size. It was just like if it was burning, but we could not see any flame — it was almost like an invisible flame was causing these heptane droplets to burn steadily,” Williams says. “We didn’t even believe it for a year.” The team’s research was published in the December 2012 issue of the journal Combustion and Flame.
“Cool flames” have long been known to exist, but understanding more about how they work could help in the development of efficient, low-emission engines. Alternative fuels used by these types of engines often produce cool flames during combustion.
“If we hadn’t done these experiments in station, this phenomenon [that cool flames can support steady droplet combustion] would not be known today, so we were really excited about that,” Williams says.
Rebecca Boyle is an Air & Space contributor based in St. Louis.
September 10, 2012
Shortly after Japan’s Kounotori cargo ship undocks from the space station on Wednesday, ground controllers will fire its rockets to steer the schoolbus-size craft into the atmosphere so that it burns up over the ocean. Normally, the end would come discreetly off camera. This time, we’ll get to watch the fireworks.
In the 55-year history of satellites re-entering the atmosphere, nobody (or at least nobody in the unclassified world) has ever gotten pictures from the satellite’s point of view. For Kounotori’s demise, Japanese investigators have placed a camera-equipped device called i-Ball inside the spacecraft. The spherical i-Ball has two cameras. One will return 10 images from inside Kounotori as it’s breaking up. The second camera will take 40 pictures after the breakup, and the i-Ball will continue on to a splashdown in the ocean.
This Japanese space agency video shows how it’s all supposed to go:
Japan’s i-Ball won’t be the only instrument recording the spacecraft’s breakup. Another experiment package, called REBR (Re-Entry Breakup Recorder), will collect information on temperature and accelerations as Kounotori is torn to pieces during re-entry.
“Getting data off a satellite that’s coming in and breaking apart is a bit of a trick,” says William Ailor of The Aerospace Corporation, principal investigator for REBR, whose team worked on the technology for more than a decade before flying it for the first time on another Kounotori last year. REBR is contained in a copper shell held together by plastic bolts. Once the spacecraft starts to break up, the bolts melt and the instrument package is set free. “The whole vehicle that we’re riding in has to come apart for us to get out at all,” says Ailor. REBR has no cameras, but its data — transmitted to the ground during a five-minute fall to the ocean — will tell scientists about the timing and conditions of the breakup.
Why do they care? Currently, spacecraft operators err on the side of caution when it comes to de-orbiting a satellite at the end of its lifetime. Rather than risk an uncontrolled entry over a populated area, they command the satellite to re-enter slightly early. “If your casualty expectation exceeds 1 in 10,000, you have to put it in the ocean,” says Ailor. The risk of casualties is based on estimates of when a given satellite would break up as its orbit decays. “What we’re trying to do [with REBR] is calibrate the models that make these estimates.” If satellite owners could be less conservative in their estimates, they could leave valuable satellites — say, the Hubble Space Telescope — operating longer in space.
Information on satellite breakup is considered important enough that a commercial venture called Terminal Velocity Aerospace has licensed the technology from The Aerospace Corp. to do routine data collection on future spacecraft. Meanwhile, Ailor is looking forward to i-Ball’s first-time photos. “I hope they succeed,” he says. “That will be really significant in itself.”
Below: In 1984, cameras in Hawaii captured the space shuttle’s external tank breaking up over the ocean. The STS-41C astronauts narrated video of the re-entry during a postflight press conference:
In 2008, the European ATV cargo vehicle was filmed during re-entry:
Next Page »