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#TFW it is dark and your kids call because they are stranded on a tiny island in the middle of the whirlpools that keep sucking the kayak away from shore and they couldn't paddle hard enough against the tide to get home and as last resort they want dad to come with the boat.🙉 /1
2/ (These are the older kids. Not the two young ones who went out for the first time this morning.)
3/ As a kid, I would have chosen death before making that phone call. But then, we didn't have phones, so we couldn't get a rescue anyway. 🙉
**Sigh** I got blocked by @Google Scholar for doing too many searches on "kleine planeten" (which means "small planets" in German), and I've done everything I can to get unblocked. To meet the journal editor's deadline I have to do the research via a phone. #ScientistProblems
2/ Problem solved. Thank you all for the great suggestions! When I tried it in Google's Chrome browser, Google offered me a recaptcha to prove I am not a robot. It didn't offer me that as long as I was using Firefox. #GoodToKnow
3/ I should add, Google Scholar thought I was a robot because I use it so dang much, because it is amazing for searching in particular years & languages for specific phrases, parsing results narrowly for statistical insight. New science is possible that never was before...
The NASA Ames Research Park on Moffett Field is Old California on the edge of space. 
In case you were wondering, NASA does have a bicycle distribution facility.
And the landscapers at NASA Ames were influenced by Dr. Seuss.
coffee ($5) or help for the 
server cost ($10):
Friends tell me I should've explained why I unfollowed from 35,000 down to <200 accounts. I humbly apologize. I used to follow back 100% to communicate true respect. 4 years ago I simply couldn't keep it up. It took HOURS to identify & NOT follow objectionable robot accounts.../1
2/ I was forced to give up. I had to stop following back entirely so I wouldn't accidentally follow bots tweeting bad stuff. Out of a desire to not offend I didn't unfollow any existing follows, but after 4 years I was following less than half the people who followed me...
3/ The twitter feed had become a firehose that I couldn't possibly keep up with. My interactions on twitter were reduced to just responding. Reply to everyone who tweets at me, and answer every science question (except when overwhelmed by work & simply can't keep up)...
This tech is cool. Photons (light particles) from a warm body tend to be maximally random. Very simple math proves that "maximally random" is when more photons are at one wavelength than another. It is the most probable spectrum. The shape of this spectrum tells temperature! /1
2/ It might seem weird that the "maximally random" spectrum does not have an equal number of photons at every wavelength. For comparison, if you roll 6 million dice, you will get one million 1's, one million 2's, etc, an equal number in each possible state. Why not for photons?
3/ Becoz different wavelength photons carry different amounts of energy. The higher the wavelength, the more energy the photon carries from your body. If you were radiating as many high wavelength photons (x rays) from your body as low wavelength (IR), you would instantly freeze.
At the airport again. This time going to Silicon Valley for the Frontier Development Lab to mentor a team of researchers creating artificial intelligence for lunar roving and prospecting vehicles. This will be fun!
2/ Something I am wondering... Back when I was on the International Space Station program we all traveled A LOT. We had to go to contractors all over the country to make sure the thousands and thousands of parts and assemblies were on schedule and passing checkout requirements...
3/ Then we had to make sure that when the parts got put into black boxes, those boxes passed their tests, and when those boxes got put into racks, and the racks got put into modules of the Space Station, every level of assembly was on schedule and passing all tests...
I agree, but in any case it makes no sense to keep civilization on just one planet, because doing so hurts the planet, hurts the people, and prevents all the amazing things we could be doing if we weren't so-limited. /1
amp.businessinsider.com/fermi-paradox-…
amp.businessinsider.com/fermi-paradox-…
2/ I mean, the planet sets a DEFINITE limit to the size of things we can do in this universe. We can't build telescopes bigger than a planet until we get off the planet. We can't build supercomputers to solve super science questions if they need more energy than a planet. Etc.
3/ And we could never afford to build those giant telescopes, or giant supercomputers, or traversing world ships to comfortably take communities to other stars while we have an *economy* limited by the scale of a planet.
Today, writing software to simulate small spacecraft extracting water from asteroids. It took 2 weeks to develop equations of thermal conductivity as gas pressure increases in the soil. Finally got the code running! Here is gas pressure developing in & around the coring device:
2/ Granular materials like asteroidal or lunar soil are really good thermal insulators, especially when they are in the vacuum of space so there is no air between the grains Pro tip: if you're stranded on the Moon & need to stay cool in the harsh sunlight, bury yourself 1 m deep.
3/ Therefore it is hard to heat the asteroid's soil to get the minerals to release the trapped water. You can apply heat to the soil, but it takes a LONG time for the heat to travel into the soil. This could waste LOTS of energy as you try to get water.
Visiting Puerto Rico with @sheyenegerardi at @NAICobservatory and a university to develop plans for our program of Planetary Engineering and robotics education. It has been amazing! More later...
2/ We had an AMAZING meeting with the @NAICobservatory director and @UMET_PR Chancellor. We all agreed to move forward developing a Planetary Engineering education initiative with robotics competitions connected to the observatory. Our program is moving faster than I expected!
3/ The sign includes the @UCF logo since UCF won the contract to manage it. The National Science Foundation is greatly reducing funds to support it 😞, but UCF is developing new revenue streams to keep it open and healthy. This is why @sheyenegerardi and I were invited to visit.
Breakout sessions at the lunar volatiles prospecting workshop. Our group is assessing Phase B: after orbital remote sensing (Phase A) but before high capability rovers (Phase C) finalize the 1 sq km mine location. #2018SRR
2/ Our group focused on (first) swarms of small impactors to burrow into each of 3 craters that Phase A had selected as locations of high hydrogen. The impactors will seek to Monte Carlo measure water concentration, chemistry and variability over the crater, plus soil mechanics.
3/ Then (second) we would send a static lander or a hopper with more advanced instruments to the best of these three craters to better constrain the water's variability and its physical form. We are working to define the instruments. But the iverall ideas are still evolving, too.
"Closing the business case for mining propellants on the Moon," by @george_sowers, formerly chief scientist of @ulalaunch now faculty at Colorado School of Mines.
2/ The concept is not to use rovers that dig and haul regolith with ice to a processing plant, but instead to heat the ground with mirrors and capture the sublimed vapors in a tent as it diffuses from the ground.
3/ Julie Brisset & I at @UCF are funded to do physics-based computer simulation of this process in collaboration with them. More work is needed, but so far the results are very promising. There are enough "knobs" to turn in the design that we feel confident we can make it work.
I'll reply to this tweet with some Scanning Electron Microscope pictures of Surveyor 3's surface before and after sandblasting by the lunar soil blown from the Apollo 12 landing. It's extremely interesting!
2/ This is a super-magnified view of Surveyor 3's white paint where it was NOT sandblasted with lunar soil. The round balls are the normal way the paint dries, though our unaided eyes can't detect it. Cool, right? Next, what lunar soil does to the paint...
3/ Now here is the same paint in an area where it got sandblasted by lunar soil blown from the Apollo 12 Lunar Module landing. The paint's natural texture got crushed, and lunar soil particles are mixed in the surface.
I'd like to share the story of a personal interaction I had Alan Bean, Apollo Moon-walker and artist. In 2010, I needed more information about something Alan had seen when he was on the Moon. I was researching how rocket exhaust blows soil and dust during lunar landings. /1
2/ The best information on this topic was from Apollo 12, when Pete Conrad and Alan Bean landed their Lunar Module 160 m away from the old Surveyor 3 ("S3") spacecraft. S3 had sat on the Moon deactivated for about 2 and a half years exposed to the lunar environment.
3/ The Ap12 mission was planned to land near S3 to (1) demonstrate precision landing and (2) to cut pieces off S3 and bring them back to Earth to see how the lunar environment degrades various types of materials and spacecraft parts.
1. A thing ppl may not realize about the canceled lunar mission: NASA probably cancelled it to save funds for the SLS rocket. But, SLS will end up being marginalized with only @elonmusk BFR doing Mars missions unless we can make Mars missions affordable w/in NASA's risk profile.
2. So NASA needs to change the game to make Mars more affordable, or SLS will ultimately be marginalized & never do Mars surface missions. There is only ONE serious idea to make Mars affordable for NASA, and that is to develop a vibrant cislunar economy involving space resources.
3. How can a vibrant cislunar economy make Mars more affordable for NASA? Multiple ways. Provide propellant made in-space to avoid launch costs. Cheaper in-space assembly of spacecraft. More space activity so economies of scale reduce overall cost of doing business in space. Etc.
1. Wanna hear a weird but true story? (I have a few minutes to type, so here goes). I almost lost my hearing from the lid on the tank of a toilet. Noise-Induced Hearing Loss. You wouldn't think a toilet lid could be so loud, would you? Well, I learned otherwise...
2. I was fixing the mechanism inside the tank of the toilet. The only thing left to do was to put the ceramic lid back on the tank. Unfortunately it slipped out of my hands and banged on the ceramic of the toilet rim. Again, you wouldn't think that would be so loud, would you?
3. Well, the sound stunned me. I stumbled out of the bathroom and fell to my knees in the living room, wondering what had just happened. Did something happen, or did I imagine it? It was surreal. Then I got the idea to test my hearing, because I noticed something seemed weird.
I looked into it and was told the last surviving Lunar Module telemetry tapes were stored in a missile silo and were old so the magnetic material was coming off. To read them we’d need to develop a procedure to bake the tapes, re-adhere the material. Then...1/n
2/n then we could play them back, but the last surviving tape player for that type of tape was in Langely, Virginia, so we’d need to ship them there and send funding. Then after reading the data we’d need to figure out what data formats the Lunar Module was using...
3/n. A data format is how the vehicle selects which of the thousands of possible measurements it could send back to Earth in any particular period of the mission. Data formats are all defined in this documents we would need to track down...
Another story on forgotten requirements in the space program. During NASA’s Constellation program, we all knew the Apollo Lunar Modules had a requirement that they couldn’t land on terrain more sloped than 11 degrees. (Or was it 10.5? I’m no longer sure.) But nobody knew why. 1/n
2/n Even the lead designer for the Altair lunar lander told me that he didn’t know why Apollo Lunar Landers had that requirement, although he knew that it was in fact their requirement. It was another requirement whose rationale was long lost in the mists of time.
3/n One reason we talked a lot about that requirement was because it almost got violated during one of the Moon landings: Apollo 15. That mission, lunar module blew so much more dust than most other landings (except Apollo 12) that they couldn’t see what was beneath them.
Strange but true story: the giant round propellant tanks at the Apollo/Space Shuttle launch pads were certified to be emptied & refilled only 6 times. Nobody could remember why the number of refills was limited, but they were dutifully kept full of liquid oxygen for 40 years. 1/n
2/n. Nobody knew where the requirement originally came from, way back in the 1960’s. Was it a structural limit, the steel would get too weak if warmed then re-chilled to liquid oxygen temp more than 6 times? Nobody still living knew.
3/n The requirement itself was documented since the 1960s, but the reason behind the requirement was as lost as ancient texts in the Library of Alexandria. So we dutifully obeyed for DECADES keeping those tanks full without ever knowing why.