Some spaceflight stuff

NASA is to hold a news briefing on an upcoming spacewalk by astronauts Doug Wheelock and Tracy Caldwell Dyson, aboard the International Space Station. The briefing will take place at 1pm CDT on the 3rd of August and will be broadcast on NASA TV. The spacewalk, at 5:55am on the 5th of August, will be in support of the European built Columbus module, which will be slotting onto the station soon, as well as outfitting the Russian Zarya module for robotics work.

A few NASA astronauts have been here and there meeting members of the public. At this event, T J Creamer discussed his time on the ISS as part of the Expedition 22/23 crew with followers of his twitter feed, which sent back the first live tweet from space. Meanwhile members of the STS-132 final full crew of the space shuttle Atlantis were asked an interesting question at the National Air and Space Museum – what does it take to be an astronaut? I’m sure they all resisted the temptation to say “a big rocket”. You can learn more about NASA astronauts at this website.

Of course, big rocket implies big explosion, which is why safety features have to be included in space missions. Ejector seats can’t happen as these require windows that weaken the hull. For the space shuttle, the only way out was through a hatch with a parachute and hope the thing is in the process of landing and within six kilometres of the ground (but not too much within). The traditional design for helping astronauts off an exploding, launching rocket is a Launch Abort System that sits on top of their capsule and carries a number of smaller rockets. Should something bad happen (as shown below), the capsule blasts away from the firework beneath it. The trouble is, having such a thing on top of the capsule affects how the rocket moves, adds weight and means dumping a load of equipment after a certain point in the launch. Boeing think they have an alternative for their new CTS-100 capsule. Called a pusher system, rather than having rockets on top, this one uses thrusters beneath the capsule. This enables a successfully launched capsule to use the abort fuel for movements in space, though it does entail keeping the volatile mixture in the spacecraft.

Mars Exploration Rover Opportunity has spotted a dust devil on Mars. Signs of the phenomena, kind of like a tornado traced by Martian dust, happening near Opportunity have been seen from orbit, but this is the first time an image has been captured by that rover itself in six and a half years of its ninety day mission. Opportunity’s twin, Spirit, lying in a dustier, rougher terrain, has seem them by the dozen, however NASA is bracing rover-huggers for the possibility that Spirit may well be seeing no more. As the Martian winter starts to fall in an area, sunlight becomes too dim for a rover to run normal operations off. Power is therefore routed to keeping everything ticking over and hopefully a little warm. During this time, the rover is hibernating, sending no signals to Earth unless there is spare power, but for a successful hibernation, the rover should be positioned on a Sun facing slope in order to catch the best of what little solar power is available. Spirit suffered wheel failures before winter set in and finally ended up partially sunk in a crater hidden submerged in the dust the rover was swimming through to get to the slope. Efforts to free the thing failed to dislodge it in time, and the rover ended up hibernating in suboptimal conditions. The earliest time that a signal from the rover could’ve been heard was July 23rd, when the Sun became strong enough to power the device again, however, it is believed that hazy skies would mean the surface strength of the Sun would be reduced, making it more likely that a September reunion between ground control and rover would happen. Either way, the rover should call home sometime before March, if it wakes up. Nancy Atkinson of Universe Today is more confident that the gloomy implications of the press release. She predicts that not only will Spirit rise once more, the little rover will enact the plans ground control have been working on to pull out of the sand-trap. Time will tell.

Not showing the least bit of respect for its elders, the ATHLETE rover, potentially to be used on the Moon or Mars, has been showing off its dexterity by dancing in a NASA video

NASA’s increasing concentration on surface missions to the red planet has had one notable casualty. The Mars Scout program was to provide the infrastructure for relatively low cost missions to Mars. Unfortunately, as more and more missions head for the surface, the price tag for the average mission has risen far higher than the cap for Mars Scout. The Scout program replaced the Discovery program, which sends stuff all across the solar system, but was barred from the Sun or Mars on cost grounds a while ago. Discovery missions can now go back to Mars, but the budget for them is lower even than for Scout missions. The final Scout project is set for launch in 2013. More details here.

Even further out and the Cassini probe has been studying Titan’s dunes. The dunes of Titan are 100 metre mounds of hydrocarbons. They are lined up by winds blowing the hydrocarbons, much as on Earth they blow sand, but careful studies of them appeared to show something a little odd. They appeared to have been created by winds blowing the opposite way to those atmospheric circulation models suggested they should be blowing. The models said winds should blow Eas-West at the latitudes the dunefields occurred at (within thirty degrees of the equator), but the dunes said West-East. Researchers went back to their models and looked at them over the course of a year and the answer popped out. During the solstices, which happen twice a Titan year, or twice every twenty-nine Earth years, there is a transitional period of one or two years where the winds blow the wrong way. Furthermore, these winds are stronger, blowing 1-1.8m per second. The normal winds blow at less than 1m a second, which is below the threshold for dune creation out of the cold hydrocarbon mush. Meanwhile on the moon Rhea, it is what Cassini hasn’t seen rather than what it has that is interesting. Previous studies of charged particles around Rhea have shown a drop in the number of electrons around the equator. One explanation for this, put about in 2008, was that there may be rings around Rhea, the first ever ringed moon. Cassini then conducted a number of observations designed to look through the haze of any rings composed of small particles to see their effect on Sunlight passing through (as it did with the jets of Enceladus) as well as taking images at less severe angles to try and spot larger objects reflecting a little light. Nothing has been detected at all, never mind a set of rings.

And finally, the Spitzer Infrared Space Telescope has been giving us views of the universe through infrared eyes. One of its present missions is to create a survey of the Milky Way. It has done the bit looking towards the centre of the galaxy and now is doing the bit that looks away from it, learning how star formation happens in areas of the galaxy that aren’t as dense as the rest. It has spotted some pretty big stars, twenty times the mass of the Sun, and astronomers would like to know how they came about.


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