Wednesday, October 26, 2005

The Prometheus Effect

The Cassini Spacecraft has taken high resolution images of the F-ring and have figured out how the small moon Prometheus causes the structure seen in the F-ring using a simple dynamical model. A paper is being published in the next issue of Nature if you want more details than you can find on the web.

I went to a talk yesterday about Enceladus and the rings of Saturn that was very interesting as well. The Ultraviolet Imaging Spectrograph on board Cassini has imaged a torus of molecular oxygen at the distance of Enceladus and after recent flyby's of Enceladus, have found that the south pole of the moon is warmer by 20 degrees than the equatorial region. Their hypothesis explaining their observations suggests that liquid water under a cracked surface on the younger south pole (compared to the cratered and obviously older surface elsewhere on the moon) is venting through the cracks with water perhaps mixed with ammonia that would be around 170 degrees Kelvin and liquid below the surface, would raise the temperature of the surface around the cracks to about 85K from about 65K as it cools to about 140K as it sputters Old Faithfull style into space, creating an atmosphere that escapes the moon and forms the oxygen torus as well as the water dissociates. The talk culminated in a discussion of the rings and it sounds like if the rings are regenerative, they could be much older than recent estimates, perhaps billions of years rather than only millions. They actually try to measure the ratio of icy ring material to contaminants from impacting meteoritic material as one estimate of age of the rings, but different ring models result in rather wide ranges of ages for the rings. Maybe they'll figure things out by the time Cassini's mission is complete. But in any case, it's really neat to see science and our knowledge of the Saturnian system growing by leaps and bounds as Cassini orbits the 2nd largest planet in our solar system. And another Titan flyby is on schedule shortly too!

Friday, October 21, 2005

HST images the Moon

Jim Garvin recently used the HST to do some minerology on the Moon, looking at the distribution of resources there. HST imaged the Apollo 15 and Apollo 17 landing sites as well as the prominant crater Aristarchus, using the first two areas as ground truth since we have samples from those sites.

The HST has a resolution on the Moon of around 90 meters, so while the landing sites were imaged, the hardware remains unresolved (no groundbased telescope today can resolve the lunar hardware, though a set of 4 telescopes in the southern hemisphere are going to be used to do interferometry with a baseline of up to 200 meters and that might get to the resolution we'd need to marginally recognize the largest items left with the crude shape of those items starting to become recognizable. While we have no chance at seeing the Apollo artifacts in these images from HST, there is a lighter discolored area in just about the right spot on the highest resolution images in the set which might be caused by the lunar module descent engine scouring the surface during the final moments of landing almost 33 years ago.

BTW, if you bring up the large image of the Apollo 17 site, the top right image showing the rover and one of the two crewmembers on the rim of Shorty crater where they found orange soil can be seen in the left image and is at the dark spot in the light landslide material that extends out across the Taurus-Littrow valley that is left of the red "X" that marks the landing site.

Wednesday, October 12, 2005

Spaceref article on ESAS

NASA has released some new details on the ESAS (Exploration Systems Architecture Study) which gives some diagrams of their current plans. While the CEV looks remarkably like the old Apollo Command Module (but on Steroids as some have suggested), and some seem to be poo-pooing the idea because it looks like a rehash of Apollo, I don't really see it as a problem. We know how well Apollo worked and it has some really great advantages. But we also see how we can improve the concepts of Apollo (for example a combination of Earth Orbit Rendezvous - EOR - and Lunar Orbit Rendezvous - LOR - is the prefered mode of travel to the Moon this time). By separating the crew and the payload as much as possible, the Crew launch vehicle (CLV) can be optimized for the task and be made as safe as possible. The Payload launch vehicle does not have to be manrated and can cary more cargo, particularly when combined with the CLV. The CEV is designed around launch vehicles and is worked backwards from what is expected to be needed to fly to Mars, so its ultimate version can carry 6 crew and earlier versions will carry 3 and 4 crewmembers. It can also be used in unmanned mode for carrying pressurized cargo to the ISS or can be replaced on the service module with a larger unpressurized cargo module. Very versatile.

The Lunar Module - this time called Lunar Surface Access Module (LSAM) - is designed to use LOX & H2 in the descent stage and LOX/Methane in the ascent stage. Methane is thought to be readily available on Mars so that they can refill the tanks with local resources there. It also uses the same engine as the service module, so presumably, they can restock the SM tanks from in situ propellant resources.

Anyway, lots of neat plans and I think its very logical and very doable with the expected resources. Can't wait to see metal being bent on these designs!