Change In Experiment Will Delay Shuttle Launch

necro81 writes "A $1.5 billion gamma ray experiment, the Alpha Magnetic Spectrometer, that was to have launched aboard the space shuttle Endeavor to the International Space Station in July, has undergone a last minute design change that will change the launch date, pushing back the end of the shuttle program by at least several months. The change replaces the original liquid helium-cooled superconducting magnet with a more conventional one, which will reduce the risks involved (superconducting magnets can be problematic — just ask CERN) and will greatly extend the useful life of the spectrometer (the liquid helium coolant would have boiled away within a few years of launch). Although the conventional electromagnet is only 1/5th as strong, its increased lifespan should allow for substantially more science to be conducted, especially considering the ISS's extended mission life. As the change is still underway, the impact to the final shuttle schedule is not fully known."

Re:Seriously?

[Anonymous Coward]

Yeah, according to Wikipedia, they are indeed swapping the cryo-cooled superconducting electromagnet for the conventional one that flew on the AMS-1. Reading the AMS website, I found out that both have the same dimensions and mechanical interfaces to the instrument, since they were developed as swappable alternatives for short- and long-lived mission profiles. However I think the overall working of AMS-2 has still changed enough (especially with the removal of the cryogenic circuitry and the change in magnetic field) for the whole integration and testing process to be redone from scratch.

Re:Contingency plans for X37B?

[Anonymous Coward]

Having a different inclination actually puts X37B out of reach of Endeavor or any Shuttle-ISS flight. These are completely different missions with no plans for any interaction between them.

Regarding your skepticism about the destruction of USA 193, I refer you to Jim Oberg's excellent summary here [jamesoberg.com]

Re:High-temperature superconductor magnets?

[wizardforce]

There are a few reasons: 1) high temp superconductors have a relatively low critical magnetic field strength at liquid Nitrogen temperatures and 2) At this point, switching to high tempt superconductors in the design would require an even longer delay due to the testing required. Of course if 1/5 the field strength is a ok then high temp superconductors should still have a sufficient critical magnetic field strength at liquide Nitrogen temperatures. Although really, you'd still have coolant boiling away just at a somewhat slower pace.

Re:Space is cold

[biryokumaru]

Space isn't actually cold. There's nothing there to be cold. In order to transfer heat, you need something to transfer it into, and there's just nothing there.

See this [irregularwebcomic.net] excellent discussion of cooling problems for the Star Wars planet-city Coruscant.

Re:High-temperature superconductor magnets?

[Anonymous Coward]

High temperature superconductors generally can't produce big magnetic fields without the superconductivity breaking down. They're fine for carrying big currents in straight lines, but they make terrible magnets. That's why the LHC's magnets are low temperature superconductors, even though this isn't a space application which had to be planned 20 years in advance.

NOT gamma-rays

[Anonymous Coward]

AMS is not a gamma-ray detector. It is designed to measure cosmic rays. http://ams.cern.ch/AMS/ams_homepage.html [ams.cern.ch]

Re:Seriously?

[reverseengineer]

That's because, contrary to what the summary says, this is a cosmic ray detector, not a gamma ray detector. The point of the big magnet is that there will be charged particles streaming through that can be steered by a magnetic field (and so identified). Of course, most cosmic rays are protons, but a significant fraction are alpha particles, and one of the major objectives of the experiment is to look for alpha antiparticles (antihelium nuclei, in other words).