The Europa Clipper stretches its wings as launch nears NASA's Europa Clipper is now less than a month from its October 10 launch, and the US space agency has shown off the spacecraft's giant solar arrays. However, concerns persist over how well the probe's electronics will fare in the harsh Jovian environment. Each of the Europa Clipper's arrays measure 14.2 meters (46.5 feet) …
“There are concerns over the transistors that help control the flow of electricity on the spacecraft.”
On the elREg, everyday you learn something new. Seriously, I would have designed them for three times the expected radiation, placed them in the most shielded part of the craft and tripled the width of the radiation shield. In space glitches come in threes.
'Most shielded part' of the spacecraft is probably where everyone wants their sensitive (but not sensor) equipment to be located*, so is a bit tricky.
I suspect that one of the reasons Voyager and other craft have lasted so long is that no one wanted their part of the mission to be the crucial bit that failed first leaving the craft a mere asteroid. These boffins** think of everything and, I have to admit, probably do a far, far better job of it than I would.
Looking forward very much to hearing about the results in a while (fingers crossed for the launch).
* A bit like when you are playing D&D and everyone says their character is 'in the middle of the group' as you explore a new dungeon. Or when designing a warship, everyone wants their radar, IR detector, etc. to be 'at the top of the mast'.
** Gender neutral term, 'coz, well, its the intellect that counts.
"Together, the arrays will produce approximately 700 watts of electricity at Jupiter, or just enough to operate a small microwave oven."
The magnetrons in microwave ovens are only about 60% efficient, so a 700W microwave would consume around 1100W. This could be a problem for anyone on board the Europa Clipper who fancies a jacket potato.
Nope, because the key number is power delivered in to the food. It's possible to make microwaves more efficient through differences in detail so if cooking instructions are based on 800W into the food, it's no good saying you need a "1200W oven" because maybe someone has an older, less efficient model that takes 1600W to deliver 800W and would leave the food undercooked, or a newer, more efficient one that only needs 1000W to do the same job and would nuke that lasagne ready meal into orbit.
We have a Panasonic "inverter" microwave (quite a few manufacturers make these now) which not only has the advantage of the "low power" modes actually being low power, rather than full power with a reduced duty cycle but is also apparently more efficient than a normal microwave. Hard to tell though because while the rating plate on the front helpfully shows 1000W microwave power, it is a combination oven, so it also shows 1000W for grill mode and 1600W for conventional oven mode which means the rating plate on the back - where the actual maximum consumption is listed - doesn't show the at-wall consumption for microwave mode. I must get around to plugging my meter in and checking.
Had an argument once with an "educator" about an example he was giving to children about cooking baked potatoes. His conclusion was that baked potatoes in a microwave were always a lot cheaper than in a conventional oven. His main mistake was to forget that a conventional oven cycles, so one hour of use does not take 2kWh of energy, it takes maybe a little over half that. His secondary mistake was to ignore the fact that every potato you add to the microwave increases the cooking time by (a little less than) the time for a single potato, and he also ignored microwave efficiency.
Put those things together and it turns out that not only is cooking seven or more potatoes in a conventional electric oven quicker than by microwave it is also more efficient (less energy consumed)*. It might actually be cheaper to cook them in a conventional gas oven with as few as three potatoes**.
M.
*assuming 10 minutes for one potato in the microwave and 1 hour for any number of potatoes in a conventional oven, at 1000W consumed (600W oven) six potatoes (approx. 1 hour) would consume about 1kWh which is likely to be approximately the same as a thermostat-controlled conventional oven (2kW heater) consumes in the same time.
**in the UK, gas has historically been between one third and one quarter the price of electricity. While gas ovens are slightly less efficient than electric ones (particularly fan models), it's not a huge difference. They don't cycle on and off like electric ovens; the regulator turns the flame down as the set temperature is reached.
There is a good writeup of the MOSFET issue here, Infineon who made the parts to US military specs found out that the parts were failing after a manufacturing change. Apparently they didn't realise that NASA was using the part for clipper so didn't bother telling them. The electronics are inside of an aluminium-zinc box which was sealed a year ago and which does offer some radiation protection.
https://www.science.org/content/article/vulnerable-transistors-threaten-upend-europa-clipper-mission
Apparently they didn't realise that NASA was using the part for clipper so didn't bother telling them
I don't know if it's that simple? Infineon got classified information about failures in military spy satellites, but didn't publicize that information. Actually, that kind of information is pretty tightly controlled (a known weakness of military intelligence).
Great link! It has this wonderful line (on top of: "Jupiter’s magnetic field is 20,000 times stronger than Earth’s"):
'But at its most simple, the problem is easy to understand, Fitzpatrick said at the meeting. “A switch would not work when we need it to work.”'
which is reminiscent of the Raspberry Pi Pico 2's surprise pull-down resistor gpio hardware bug (RP2350) ... but at the complete opposite end of the scale!
Given that this was all found out after several US military satellites died in orbit I assume there is a closed door negotiation going on around the compensation. Also this will effect their vendor reliability score which will push down the price the US government is going to pay them for parts in the future since they will now need to test parts after delivery.
This will end up costing Infineon far more than they saved.
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