Space Station Prepped for Six Crew Members

On May 29, the crew of the International Space Station (ISS) will double, from three astronauts to six. In a media briefing held today, NASA said that it has accomplished the necessary tasks ahead of Expedition 20--a Soyuz mission that will carry the second half of the crew, scheduled to launch on May 27. Not only will this complete the station's first six-person crew, but the mission will be the first time that crew members from all five ISS partners--Japan, Russia, Europe, Canada, and the United States--are aboard.
Increasing the crew capacity of the space station is a major advance for space-science research and for travel beyond low Earth orbit to the Moon and Mars. "It opens up more possibilities, such as scheduling more science, because we don't have to use all our people for just required maintenance to the station," said Courtenay McMillan, Expedition 20's lead flight director, during the briefing. But, she added, it also presents communication challenges: "Now we have twice as many people and not as many phone lines." When the shuttle or Soyuz spacecraft docks with the station, there are short periods of time when there are six or more astronauts aboard the station, using the additional spacecraft for support. However, it's only for a week or two, and then three astronauts remain living on the station.
The expansion of the station meant modifying its life-support systems. Most notably, NASA built a comprehensive water recovery system that uses specially designed filters and chemical processes to cleanse waste liquids--astronauts' urine and perspiration--so that they become drinkable water. The system has had a few technical difficulties, but according to Dan Hartman, manager of Integration and Operations for the ISS program, it should be operational by next week. A new toilet, crew quarters, galley, and treadmill (named after comedian Stephen Colbert) have also been developed to support the additional crew members.
NASA's main concern, should missions to resupply the station be delayed, is food. "We can handle a month-period slip for resupply, and if that time was going to be extended, then we would react by using other missions," said Hartman at today's media briefing. NASA has acquired a robotic spacecraft from Japan--the H-II Transfer Vehicle (HTV)--to resupply the station in between scheduled shuttle missions. The HTV will connect to the Japanese Experimental Module (JEM), called Kibo, and will be "a major new capability to resupply the station, allowing for the launch of rack modules and external and internal payloads," said Hartman.
"The logistics are done, and we have the supplies ready to expand the crew and allow them to stay for an extended period of time," added Ben Pawlik, Expedition 20's increment manager, at the briefing. The station will even have room to support seven additional crew members when the shuttle docks at the ISS.

Space sail could bring used rockets back to Earth

THE risk to spacecraft from a collision with space debris could be reduced by equipping launchers with a gossamer-thin "sail". The idea is to deploy the sail after the rocket has released its payload to amplify the drag of the last vestiges of the atmosphere, and so force the rocket out of orbit.
Rocket stages are a particular risk to spacecraft because they often contain large amounts of unused fuel, which can explode when sunlight heats the tank. Leaking fuel can also act like a mini-thruster, pushing the rocket into an orbit where it may cause a collision. One way to tackle the problem is to vent unused fuel in a controlled way, and drain power from the battery, but this is unlikely to eliminate all collisions.
Now space-flight engineers Max Cerf and Brice Santerre at the European aerospace firm EADS Astrium are devising ways to build a sail that would quickly remove a spent rocket from orbit. The sail or "aerobrake" would be deployed after a rocket has delivered its satellite into low-Earth orbit, slowing it down by friction with the thin atmosphere so that burns up in around 25 years, much earlier than conventional rocket stages, some of which are expected to survive for at least 100 years.

For the final stage of an Ariane 5 launcher, the conical sail would need to have an area of about 350 square metres and be supported by an inflatable mast 12 metres long. Cerf and Santerre propose a number of possible ways to build the mast. The simplest envisages a woven polymer and aluminium tube that is kept inflated by nitrogen gas. Another uses a tube made of polymer composite, which after being inflated with nitrogen is set hard by the sun's ultraviolet rays. A third design uses epoxy resin that is set hard by solvent evaporation.
The pair revealed their designs at this month's Fifth European Conference on Space Debris in Darmstadt, Germany, organised by the European Space Agency.
It's a good idea, says Peter Roberts, a space-flight engineer at Cranfield University in the UK, who is working on similar technology for small satellites. "The risk of fragmentation of end-of-life spacecraft due to impacts from other debris can be greatly reduced by deploying a drag sail."

Titanium reveals explosive origins of the solar system

The solar system emerged from a well-blended soup of dust and gas despite being cobbled together from the remains of multiple exploded stars, new meteorite measurements suggest.
Meteorites form a fossil record of the conditions that existed when they formed. By looking at the chemical makeup of some rocks, evidence has mounted in recent years that sun and the rest of the solar system formed from a cloud of debris blasted away from a number of supernovae.
But it is still unclear what that cloud – the solar nebula – looked like or how many stars might have been involved in the Sun's birth. Now, a team led by Martin Bizzarro of the Natural History Museum of Denmark has found one clue.
Bizzarro and colleagues measured the levels of titanium in meteorites from the moon and Mars as well as inclusions in some meteorites that are thought to be the oldest rocks in the solar system.
Stable forms
Titanium is a good probe for conditions billions of years ago because it does not evaporate easily. It also has a number of stable isotopes – forms of the element that contain different numbers of neutrons – that can be used to cross-check each other.
Although the concentration of titanium varied from rock to rock, the team found that two isotopes of titanium – titanium-50 and titanium-46 – were always found in the same ratio.
"It is quite astonishing," since these two different isotopes probably formed in different stellar explosions, Bizzarro told New Scientist. Titanium-46, which contains 22 protons and 24 neutrons, is created inside the cores of massive collapsing stars.
Titanium-50, which contains 22 protons and 28 neutrons, is commonly created when white dwarf stars explode as type Ia supernovae after gorging on a companion star.
Well mixed
If these two types of titanium come from two sources but are always found in the same ratio, the solar nebula must have been very well mixed. The level of mixing seems to exceed what meteorite researchers have seen in the isotopes of other elements, Bizzarro says.
"People thought that the isotope anomalies typically reflected that the cloud from which the solar system formed was not very well homogenised," says Bizzarro. He suspects the differences that are seen between the planets, asteroids, and other rocks came later, when the young sun was more active, sending out vaporising solar flares.
Stray cloud
But there may be alternative explanations for the seemingly universal ratio of titanium concentrations.
The mix could also be explained if a stray cloud of dust containing both varieties of titanium hit the early solar system, says Jeff Hester of Arizona State University in Tempe.
"Then you could have wild inhomogeneity in how the dust was distributed in the solar disc, while preserving the association between the two isotopes of titanium," he says.