Posts by TDahl

Half a kilo of cosmic nuclear fuel reignites NASA's deep space dreams

Re: significantly lower power degradation over time

The approximately 88-year half life of Plutonium 238 is a certainly major limiting factor on the useful life of an RTG, but not the only factor. Helium gas is produced by the fuel decay (when a Plutonium 238 atom becomes Uranium 234 by emitting an alpha particle - a Helium nucleus). This tends to reduce the electric output because Helium gas has a relatively high thermal conductivity, which (slightly) reduces the temperature difference between the hot and cold ends of the thermoelectric conversion elements within the RTG. The lower the temperature difference, the less electricity is generated via the Seebeck effect. See: https://en.wikipedia.org/wiki/Thermoelectric_effect#Seebeck_effect

To counteract the buildup of Helium, some RTGs (in particular the SNAP-19 Viking RTG) had a reservoir of mostly Argon gas atop the RTG housing that would very slowly permeate through a Viton O ring into the RTG housing. Argon's lower thermal conductivity helped to maintain a higher thermal gradient across the thermoelectric couples.

Another life-limiting factor is degradation of the thermoelectric elements due to continuous exposure to high heat. The materials tend to very gradually sublime, which reduces their mass and thus the resulting magnitude of the Seebeck effect.

Swedish data centre offers rack-scale dielectric immersion cooling

Re: De-ionised water works OK

In the late 1990s at DEC, we had a prototype AlphaServer that was water-cooled. The server (a 6U or 8U rack-mounted model as I recall) was sealed in a clear plexiglass/perspex box which was fitted with a number of spray nozzles. Deionized water was circulated directly in, on, and through the complete server chassis, circuit boards, everything soaking wet under a fine blast of water. It was freaky to see it running.

I think "SprayCool" was the planned branding, but it was not brought to market by DEC. A brief web search reveals a product line with the same name offered by Parker Aerospace for electronics gear today; I don't know if there is any relation to DEC's earlier work.

Martian microbes may just be resting – boffins

Been there, done that

"Until someone arrives on the surface of the red planet with a drill capable of going deeper than the rock botherers of rovers have managed so far, and a set of instruments to perform the analysis, the theory will have to remain informed speculation."

Starting in 1976 Viking landers 1 and 2 used their surface sampler scoops and backhoe shovels to dig trenches a few inches deep in the Mars soil and collect previously-buried samples that were analyzed by the Viking Lander Biology Instrument onboard each of the two landers. Most scientists familiar with the analysis found the results inconclusive, though one of the principle investigators remains convinced that a clear signature of biological activity was detected. I'm a huge enthusiast in the Viking missions and recently created a video that describes the lander's surface sampler hardware in detail (including the trenching activity): https://youtu.be/4c5o6jaJOuI

Finally – from brandbox to whitebox: Storage fabric is SDS realised

Image Manipulation

The real problem with this article is found in the image of shelved items chosen to introduce it. The right-most quarter or so is a mirror of the left third of the image. FAKE NEWS. :-)

VMS will be ready to run on x86 in 2019!

Re: Not quite

Correction: the Alpha architecture (and processor implementations) support four (4) modes: user, supervisor, executive, kernel. OpenVMS on Alpha uses all four modes, as it does on VAX.

40 years ago today the US govt sent a taxpayer-funded robot to invade an alien hostile world

Viking Lander 3D Model

Regarding the "scratch the surface" of Mars comment: The lander surface sampler (scoop) backhoes were used to dig trenches six or so inches deep, from which soil samples were collected for analysis.

The Viking project was an incredible engineering and scientific success, expanding humanity's knowledge of Mars enormously. I recently attended the 40th anniversary celebration in Denver Colorado, near the Lockheed Martin (then Martin Marietta) plant that designed and built the landers. Also attending were dozens of people who worked on the project back in the day, and it was a pleasure to meet some of them in person. I was a teenager in 1976, and I recall watching the first picture from Viking 1 emerge on the TV. Fantastic! I've been interested in Viking ever since.

In recent years I've been seriously researching the lander hardware, to help document and preserve its legacy. I have been creating a high-fidelity 3D model (using SketchUp) that is about half done. Here are a couple of videos I've created. The video descriptions on YouTube include links to the actual SketchUp model file and to the research material I have collected.

Animation of lander leg mechanisms: https://youtu.be/tKiiQpMdnTM

Making-of video: https://youtu.be/1vyzoWudom8