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48

The speculation is that Galileo gradually sunk into thicker layers of Jupiter body, and eventually reached level where pressure squeezed its RTG battery so much the plutonium went supercritical. Galileo was powered by RTGs. That is a heat source powered by the decay of Plutonium-238. Nuclear decay rate does not change. It isn't affected by pressure, ...


30

The Galileo probe carried two radionucleid batteries, each one carrying 7.8kg of Plutonium-238. But Plutonium 238, while radioactive, is not the kind of Plutonium used for nuclear bombs. That's another isotope: Plutonium-239. That's a big difference, because only the kinds of Plutonium with odd isotope numbers are fissile. Fissile means, that they are ...


28

The performance of Shuttle-Centaur would have greatly exceeded that of either the Atlas-Centaur or Titan-Centaur combination. Neither the Atlas nor Titan were able to put a fully fueled Centaur into Earth orbit using only their lower stages. The Centaur would have burned part of its propellant completing the orbital insertion. In contrast, the shuttle ...


12

Generally speaking, all "air-tight" containers leak to some small degree. On Earth this manifests itself as an inability to maintain a vacuum indefinitely; in space, it manifests itself as an inability to maintain an atmosphere indefinitely without a source of replenishment gases (which themselves are going to leak over time, so you are really only delaying ...


8

As both @AlanSE and @Philipp said, Pu-238 won't go boom no matter what you do to it. However, lets pretend it was Pu-239 and see what happens. First, the battery puts out only about 1/2% of the power of a Pu-238 battery, Galileo doesn't work at all. Second, while it is just barely possible to make a mass supercritical with pressure, you would have to ...


6

Galileo constellation is not complete (you can check its status here), so the official coverage data doesn't seem to be published yet. According to European Space Agency, Galileo should be usable by 2020. ESA have been performing positioning tests of their system since 2013 which were carried out in several EU countries. According to the following plot ...


5

It boils down to: how much spacecraft resource is required by the attitude control method you propose using? And sometimes the mission's pointing requirements play a significant role. Thrusters use propellant. Reaction wheels (and momentum wheels) use electric power. Spin stabilization uses neither, as long as you don't need to repoint the spacecraft — but ...


5

Galileo could even have filmed its fall into Jupiter if it had a good camera for that. Why wasn't that planned for Galileo? Because it wasn't possible for the Galileo Probe, which did not have a camera (good or bad), and it wouldn't have made sense (it wouldn't even have worked) for the Galileo spacecraft. The Galileo Probe and the Galileo spacecraft are ...


5

I think the overarching consideration is that it wasn't thought that a worthwhile picture would be obtained, and transmitting the picture would compete for bandwidth with more "interesting" instruments in the last seconds before the spacecraft were destroyed. There are a variety of reasons to suppose you couldn't get a good image. The spacecrafts' camera ...


5

Yes. Ulysses was quite a light weight, only 370 kg. For comparison, the Galileo probe, which was put in to Jupiter's atmosphere, weighted almost that much, and that was a small part of Galileo, which in total weighed about 2562 kg. Much of that mass was to orbit the planet, also the communications was supposed to be better, as the prime part of Galileo was ...


3

It looks like Juno has a much lower apoapsis (e.g., http://spaceflight101.com/juno/juno-mission-trajectory-design/) than did Galileo (e.g., http://solarsystem.nasa.gov/galileo/mission/journey-orbital.cfm). However, Juno is only scheduled to undergo 36 orbits while Galileo went through 34, so similar but the higher apoapsis of Galileo resulted in a longer ...


3

I am not 100% sure but I think we are looking at the aperture cover. In the picture below I've pointed out what looks like hinges (top) and a latch (bottom). There's a cutaway of the scope here which does not show such a large obstruction. Source: https://dspace.mit.edu/bitstream/handle/1721.1/114747/Carlton%20Extended%20Abstract_Submitted_v2.pdf?sequence=...


2

According to the Galileo Wikipedia article under Reconsideration-Paragraph 6 (https://en.wikipedia.org/wiki/Galileo_(spacecraft)#Reconsideration), there was consideration that Galileo could of been launched by a Air Force Titan IV-Centaur G in May 1991, but the AirForce could not provide NASA a Titan rocket due to the backlog of Department of Defense Payload....


2

Appreciate all the discussion on this. To try to summarize: Today's electronics are designed to work in a vacuum. It's still possible there are some situations where it's desirable to seal the electronics to reduce outgassing that could affect some sensitive sensor. I imagine space telescopes might want to seal their electronics - though still perhaps with ...


2

Data for planetary missions is stored in the Planetary Data System. This has an entry for the Galileo probe. Within the data files for the tmospheric Structure Instrument (ASI), there's a file called accel.txt which describes several files that contain acceleration data. Data in these files, e03z1.dat, e03z2.dat, e03an.dat, contain data for all of ...


2

Most modern spacecraft have their electronics work in a vacuum state, at least most of them. Particularly things with moving parts, like Reaction Wheels, might require some atmosphere. These small components are the only components that are sealed, all others are opened to the vacuum of space. Very early spacecraft were not designed as such. I can't ...


1

See a related question. Navigation satellites systems need a very precisely predictable orbits. A low orbit is influenced by not precisely predictable drag. A higher orbit is necessary to keep the influence of drag very low. To limit the number of necessary satellites, a high orbit is necessary too. A larger distance to ground increases the area on Earth ...


1

This is a bit of a tangent, but the Voskhod manned spacecraft had a pressurized electronics chamber. It used vacuum tubes and they were cooled with blowing air. I suppose this air must have also gone over a heat sink or something. Not sure how that worked.


1

Mechanical bearings are a problem in the vacuum of space. Grease will vaporize. If thin oxide layers on the surface of metal parts are removed by friction, cold welding of those parts is possible.


1

Using a pressure vessel for electronics is rare. I know of only a few spacecraft that did it: Sputnik 1, the Lunokhod rovers and the Venera probes.


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