Mars rover's "6 minutes of hell" 'R over

[Dubslow]

Originally Posted by Uncwilly

Because most people do not know or care what an RTG is. It only complicates things. If you said that is thermo-electrically powered, most people would have less of an idea how it works. It is fission powered, which is what most people know as 'nuclear powered'.

Radioactive decay != fission, that's my whole point; no nuclei are being split.

So it's false to say 'nuclear powered', using the common defition (e.g. Wikipedia: "Nuclear power is the use of sustained nuclear fission to generate heat and electricity.")

[LaurV]

Originally Posted by Dubslow

Radioactive decay != fission, that's my whole point; no nuclei are being split.

[Uncwilly]

Originally Posted by Dubslow

Radioactive decay != fission, that's my whole point; no nuclei are being split.

Originally Posted by http://en.wikipedia.org/wiki/Nuclear_fission

In nuclear physics and nuclear chemistry, nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts

So it's false to say 'nuclear powered', using the common defition (e.g. Wikipedia: "Nuclear power is the use of sustained nuclear fission to generate heat and electricity.")

You are referring to "Nuclear power", not "nuclear powered". The Sun is nuclear powered, but does not use "nuclear power" as described in the article on electrical power generation.

[Dubslow]

Originally Posted by Uncwilly

Hmm... from the article we get this:

The unpredictable composition of the products (which vary in a broad probabilistic and somewhat chaotic manner) distinguishes fission from purely quantum-tunnelling processes such as proton emission, alpha decay and cluster decay, which give the same products each time.

That's seems to be contradictory to the part where it says decay is fission, because decay processes are predictable and have the same results each time (the timing of the decay is random). Fission, as the quote says, does not produce the same products each time. Pu-238, powering Curiosity, primarily undergoes the predictable alpha decay (though the article has some troubling information about its production).

I don't think I've ever seen radioactive decay classified as fission... I'd love to see some non-Wiki reference on this.

Edit: The radioactive decay article only mentions the word "fission" in the context of spontaneous fission, which does not have predictable products AFAICT. That seems to me that most sorts of radioactive decay (e.g. ( decay) don't qualify as fission then.

[sdbardwick]

Look into "spontaneous fission".
Also, isn't alpha decay fission?
(Apparently not, by definition [been a while since I've thought about this])

Edit 2: Grammar...

[Dubslow]

Originally Posted by sdbardwick

Also, isn't alpha decay fission?

I would not think so: alpha decay is typically described as emission, with the nucleus the "emissee" and the alpha particle the emitted (and AFAICT there's little gamma rays or other EM radiation).

Fission, OTOH, is the (roughly) equal splitting (not emission) of a nucleus into two (random) product nuclei, along with other boson/EM radiation (mostly gamma rays).

[Uncwilly]

An alpha particle is a nuclei. No?

[sdbardwick]

I'm kinda surprised (and pleased) that they haven't resorted to calling it just a thermo-electric generator for PR purposes. Although, after seeing the reaction of people when I accidentally use the old-school "nuclear magnetic resonance imaging" (which is what it was called when I first learned about it so the name stuck), I'll bet that they are surely tempted.

[only_human]

Curiosity captures last 2 minutes of its own descent

297 frames at 4fps. Awesome.

New Mars Rover Beams Back Images Showing Its Descent

PRESS RELEASE
08.07.2012
Source: Jet Propulsion Laboratory
New Mars Rover Beams Back Images Showing Its Descent

Curiosity's Heat Shield in View

PASADENA, Calif. - Earlier today, just hours after NASA's Curiosity rover landed on Mars, a select group of images taken by the onboard Mars Descent Imager, or MARDI, were beamed back to Earth. The 297 color, low-resolution images, provide a glimpse of the rover's descent into Gale Crater. They are a preview of the approximately 1,504 images of descent currently held in the rover's onboard memory. When put together in highest resolution, the resulting video is expected to depict the rover's descent from the moment the entry system's heat shield is released through touchdown.

"The image sequence received so far indicates Curiosity had, as expected, a very exciting ride to the surface," said Mike Malin, imaging scientist for the Mars Science Lab mission from Malin Space Systems in San Diego. "But as dramatic as they are, there is real other-world importance to obtaining them. These images will help the mission scientists interpret the rover's surroundings, the rover drivers in planning for future drives across the surface, as well as assist engineers in their design of forthcoming landing systems for Mars or other worlds."

The image of the heat shield falling away is online at: http://1.usa.gov/RSVufL.
The MARDI sequence is online at: http://1.usa.gov/MZqGxv.

The MARDI camera is located on the chassis of the Curiosity rover. Just before the heat shield fell away, MARDI began its imaging task. The images selected for early downlink to Earth were taken at different points in Curiosity's final descent toward the surface. One of the earliest images shows the entry vehicle's heat shield 50 feet (15 meters) and falling away after separating from the vehicle three seconds before. A set of images demonstrates some of the gyrations Curiosity went through while on the parachute. Another remarkable set of images depicts the final moments leading up to landing, where the exhaust from four of the descent stage's 742 pounds of thrust rockets billow up dust from the Martian surface.

"A good comparison is to that grainy onboard film from Apollo 11 when they were about to land on the moon," said Malin.

Those MARDI images downlinked so far are low-resolution thumbnails, 192 by 144 pixels. In the months ahead, as communications between rover and Earth become more robust, full-frame images 1,600 by 1,200 pixels in size, are expected to provide the most complete and dramatic imagery of a planetary landing in the history of exploration.

The mission also released a higher-resolution Hazcam image of their target, the mountain in the middle of Gale Crater informally titled Mount Sharp.

The new image, taken by Curiosity's black-and-white Hazard Avoidance Cameras - or Hazcams - can be found at: http://1.usa.gov/OLB3B5 .

Curiosity, NASA's latest contribution to the Martian landscape, landed at 10:32 p.m. Aug. 5, PDT, (05:32 on Aug. 6, EDT) near the foot of a mountain three miles tall inside Gale Crater, 96 miles in diameter.

The mission is managed by JPL for NASA's Science Mission Directorate in Washington. The rover was designed, developed and assembled at JPL. Malin Space Science Systems, San Diego, provided MARDI, as well as three other cameras on Curiosity.

For more information on the mission, visit

http://www.nasa.gov/mars and

http://marsprogram.jpl.nasa.gov/msl

Follow the mission on Facebook and Twitter at

http://www.facebook.com/marscuriosity

http://www.twitter.com/marscuriosity

2012-233

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.

Dwayne Brown
NASA Headquarters, Washington

[xilman]

Originally Posted by Uncwilly

An alpha particle is a nuclei. No?

No.

An alpha particle is a nucleus.

[Dubslow]

Originally Posted by Uncwilly

An alpha particle is a nucleus. No?

Yes, but that is ancillary to the points I was trying to make, namely the difference between "emit" and "split", the (un-)predictability of the products, and the lack of EM radiation.