NASA's Mars rover Curiosity sidelined again after experiencing new problem

foxnews ^ | March 18, 2013

[UCANSEE2]

Mars is probably "so far away" for a reason. If it were significantly closer, gravitational interactions with Earth and the other inner planets could result in a chaotic orbit that would result in an eventual collision with the Earth, ruining a lot of people's weekends.

IIRC, the best guess is that this already happened.

[dfwgator]

The collision would result in a large amount of debris ejected into space, some of which will collide with Earth.

You say that as if that would be a bad thing.

[zeugma]

Interesting stuff from Wikipedia about the computers for the rover:

• Computers: The two identical on-board rover computers, called "Rover Computer Element" (RCE), contain radiation hardened memory to tolerate the extreme radiation from space and to safeguard against power-off cycles. Each computer's memory includes 256 kB of EEPROM, 256 MB of DRAM, and 2 GB of flash memory.^[29] This compares to 3 MB of EEPROM, 128 MB of DRAM, and 256 MB of flash memory used in the Mars Exploration Rovers.^[30]

The RCE computers use the RAD750 CPU, which is a successor to the RAD6000 CPU used in the Mars Exploration Rovers.^[31][32] The RAD750 CPU is capable of up to 400 MIPS, while the RAD6000 CPU is capable of up to 35 MIPS.^[33][34] Of the two on-board computers, one is configured as backup, and will take over in the event of problems with the main computer.^[29]

On February 28, 2013, NASA was forced to switch to the backup computer due to an issue with the then active computer's flash memory which resulted in the computer continuously rebooting in a loop. The backup computer was turned on in Safe mode and subsequently returned to active status on March 4th.^[15] The rover is expected to resume full operations some time next week. NASA is working on the best way to restore the currently non working computer for use as a viable backup.^[14]

[UCANSEE2]

Hard to understand how the shielding could have been inadequate, along with strategies to recover from memory errors.

Well... Plan A was to have a foot of lead surrounding the entire memory core. This would have guaranteed protection.

This had to be scaled back a bit due to lift off, landing, and power drain problems, so Plan B was chosen.

[bgill]

[UCANSEE2]

Then you will enjoy this.

http://www.360pano.eu/mars/

[cripplecreek]

I’ve been thinking about shielding.

The Bigelow space capsules and the way they’re inflated with a foam in the bulkheads. I wonder how effective it would be to infuse the foam with powdered lead.

[SgtHooper]

I bet they got some bogus Chinese parts using their Chinese outreach program.

[blueunicorn6]

It was looking at porn and got a virus.

[DBrow]

“As such, they could have designed around it sufficiently, but they apparently didn’t.”

Single event upsets are difficult to prevent or mitigate. The NASA guys in Greenbelt did years of screening and testing parts, but that will not prevent an SEU, it lets you predict them and try to mitigate with error checking and redundancy. SEU and other single event effects come from particles found in space, usually heavier than helium with a sharp numeric cutoff at iron. The heavier ones carry a lot of LET (linear energy transfer) when they hit your microprocessor.

The big problem is galactic cosmic rays (that’s the official term, often abbr GCR), which are hard to stop and can reach Martian surface. They are heavy and very energetic. The other part of space radiation (short for radiation found in space) is solar electrons and protons (in the solar wind along with small numbers of other particles like iron nuclei), and trapped particles like you find in the van Allen belts.

Yeah the terminology is “wrong” but that’s the language we use in the field.

I don’t think NASA knows what the problem is, but a good guess is radiation, either SEE or accumulated dose.

[steve86]

Are you trying to be funny?

[UCANSEE2]

No. Weight is a huge consideration on any satellite, and it would take a foot of lead(or more) to GUARANTEE protection of the electronics from ‘almost any’ kind of radiation.

[UCANSEE2]

I wonder how effective it would be to infuse the foam with powdered lead.

Sounds like a good idea, but I can't answer that question.

[steve86]

Yes, I would venture that most of we FReepers who peruse aeronautical and space-related threads are cognizant that increased dead payload weight is an undesirable in any ballistic, orbital, or interplanetary launch scenario. No one is talking about “guaranteeing” protection. It is a cost benefit engineering tradeoff, like many other areas. My statement, or what I remember of it, is that I was surprised the type and amount of shielding chosen was (allegedly) breached so early in the game.

[UCANSEE2]

Thank you for the response.

My statement, or what I remember of it, is that I was surprised the type and amount of shielding chosen was (allegedly) breached so early in the game.

I would agree except (like you mentioned) I am not sure that a breach is what caused the problem. If it was, maybe it's just that there are things we aren't aware of yet, that we didn't protect it from.

That is what I was trying to bring to light. I should have just been direct.

Maybe it was something we didn't protect it from or couldn't.