On September 26, 2022, NASA’s Double Asteroid Redirection Test (DART) spacecraft crashed into a binary asteroid system. By intentionally ramming a probe into the 160-meter-wide moonlet named Dimorphos, the smaller of the two asteroids, humanity demonstrated that the kinetic impact method of planetary defense actually works. The immediate result was that Dimorphos’ orbital period around Didymos, its larger parent body, was slashed by 33 minutes.

Of course, altering a moonlet’s local orbit doesn’t seem like enough to safeguard Earth from civilization-ending impacts. But now, as long-term observational data has come in, it seems we accomplished more than that. DART actually changed the trajectory of the entire Didymos binary system, altering its orbit around the Sun. //

Because Dimorphos orbits Didymos, some of the ejecta remained trapped in the system, where it altered the mutual orbit between the two rocks. But a crucial fraction of the ejecta achieved escape velocity from the entire binary system. The momentum carried away by the system-escaping debris is what ultimately contributed to shoving the center of mass of the whole Didymos-Dimorphos pair. “In our case, we found that the beta parameter due to DART impact was around two,” Makadia explained.

The debris blasted completely out of the Didymos system gave the asteroids a push roughly equal to the initial impact of the spacecraft itself. //

The goal of DART was primarily to take our planetary defense out of the realm of computer models and get us some hands-on, practical experience, and Makadia thinks we succeeded in doing that. “Our work proves that hitting the secondary asteroid is a viable path for deflecting a binary system away as long as the push is large enough,” he said. “This wasn’t the goal of DART, but we can always design a bigger spacecraft.”

The first form calculates the pressure or friction loss along a given length of pipeline with a specified inside diameter. The second form calculates the minimum pipe size to limit pressure loss to a specified value.

Additional friction pressure losses occur due to fittings. These losses in-effect add extra additional length to the total pipeline. Use this calculator to estimate how much additional length needs to be added to the overall pipe length below in order to estimate these additional losses. Learn more about the units used on this page.

The ONET Data Collection Program, sponsored by the U.S. Department of Labor, is seeking the input of expert Electronics Engineers, Except Computer. ONET, as the nation's most comprehensive source of occupational data, is a free resource and provides instant access to detailed occupational data covering more than 55,000 jobs that drive the U.S. economy. Our visitors include counselors, human resource professionals, veterans, researchers, developers, and students, and more. Visit the O*NET Resource Center to learn more.

Your participation will help ensure that the complexities of your profession are accurately represented in O*NET data, tools, and resources.

Fatesrider Ars Legatus Legionis
13y
24,850
Subscriptor
(An example of these types of burns can be seen here, but be warned, the image is graphic.)
On my medical professional "ick" scale of 1-10, it rates about a 3 at most.

It'd give it at least a 5 if the blisters were open and oozing. 7-8 if necrosis is involved (that shit will gag a maggot).

The other thing of note, is that though I have every sympathy for those three fishermen who were exposed to and injured by these chemical weapons over those 7 years, it should also be noted that 12 East Coast fishermen DIE EVERY YEAR (PDF) just from the regular hazards of the job. Hundreds to thousands are injured (3000-4000 off of both East and West coasts) in total annually.

So, yes, not a cool thing to have happen to anyone, but on the overall scale of "things that can hurt you", comparatively speaking on a relevant, and relative scale, you're tens of thousands of times more likely to have something ELSE injure or kill you while engaged in commercial fishing off of the East Coast than you are to have some munitions dumped by a clueless nation over the years doing you any harm at all.

Nice to know about the issue, though. And thanks for the picture. I've seen some stuff like that, usually from hot liquid burns, but it does bring back some PTSD-inducing memories.

For a generation, the FBI has kept a second set of books called 'prohibited access' files. After a long fight, they're finally being examined.
Matt Taibbi
Mar 06, 2026. //

A Federal Bureau of Investigation task force has begun excavating the separate set of books FBI keeps using an inaccessible “prohibited access” file designation, according to multiple government sources. Though an internal fight over how to handle the files continues, embattled FBI Director Kash Patel has assigned personnel to examine decades of hidden history, Racket News has learned, with some files already turned over to Congress.

“This is it — the deep state,” one of the sources said.

Judiciary Committee Chair Chuck Grassley, whose work with whistleblowers and pressure across years was key to prying prohibited access files loose, expressed cautious optimism.

“If it weren’t for whistleblower disclosures to my office, the very existence of the FBI using ‘Prohibited Access’ files for some investigations would have remained in the dark,” he said. //

Files given a prohibited access designation are not merely secret. They are “ghosts” which “do not exist,” records rigged to return false negatives when searched for in the FBI’s SENTINEL system. They’re digital descendants of paper records that as far back as Richard Nixon’s presidency were kept in locked offices, accessible to just a few officials, typically at the deputy director level and above. Currently, the number of people with the ability to access the files can be counted on one hand.

The implications of the nation’s chief federal law enforcement and counter-intelligence organization having kept a separate, non-searchable filing system are mind-boggling. //

A current government source said the prohibited access designation is “literally designed to hide files from Congress and from the FBI itself. It’s really frigging bad.”

Off-books surveillance and “disruption” of political figures in the Arctic Frost and Trump-Russia investigations comprise part of the find, but the files extend at least as far back as 1999, across Democratic and Republican Party presidencies, involving as many as a thousand distinct case numbers. There are no rules for passing access to the system from one administration to the next. Instead, operation of prohibited access files is described as an oral tradition passed down among senior FBI officials, independent of agents below and political appointees above in Congress and even the White House.

In 1971, Rev. Dr. William R. Tolbert Jr. became President of Liberia following the death of President William V. S. Tubman Sr. Departing from his predecessors, Tolbert sought to root out corruption and close the divide between the ruling class of America-Liberians, and the indigenous majority who had been marginalized since the republic's founding in 1847. Tolbert's reforms faced resistance from two fronts: entrenched elites and Western powers who saw their influence diminished, and the ethnic majority who regarded his agenda as too halting. By the late 1970s, domestic hardships set Tolbert's presidency in crisis. On April 12, 1980, the unrest erupted into a full-scale military coup when soldiers stormed the Executive Mansion killing President Tolbert and ending more than a century of Americo-Liberian rule. This was followed by the public executions of thirteen cabinet members on April 22, 1980. This is the untold story of Africa's least known reformer and the enduring societal aftermath of his murder.

Statistical Ars Legatus Legionis
15y
54,490
pseudonomous said:
I will presume that both you and the NASA guys got the math right and that for a polar landing NRHO makes sense. But if they are really going to "question all requirements", we have to admit the possibility that they might fly Artemis IV or V as an equatorial region landing, do we not?

For Orion as a crew vehicle it doesn't matter. Orion has 1,300 m/s of DeltaV of which 300 m/s is allocated for docking, station keeping, and course corrections. So it is limited to orbits which require <1000 m/s to enter AND exit (NRHO is about 900 m/s). Even equatorial LLO with a 3.5 day loiter (13 days + surface time for total mission time) is a minimum of 835 m/s * 2= 1670 m/s. Loiters improve the worst case scenario but only make a small impact on the best case ones. Even if you could modify the Centaur V to have 3 day endurance and cryocoolers and use it for part of LOI (which we shouldn't that will end up being a $5B 10 year boondoggle) it has in the ballpark of 500 m/s excess DeltaV so you are likely still short unless you dip into your reserves.

Longer term with a better crew vehicle you might have the option to go to LLO Direct via fast insertion but it still isn't a slam dunk option with reusable landers as your example bring up. If you have reusable crew landers LLO as a staging point is made worse if you change landing locations. There isn't one LLO and as such to move between LLOs you need to do a plane change. The only cost effective way to make a plane change is to burn to a highly elliptical orbit you know like how NRHO is highly elipitcal. Every mission requires more prop, has more boiloff, and when changing landing sites you also pay a plane change tax. One feature of NRHO is due to its high perilune you can reach every spot on the moon with a consistent DeltaV cost. This makes mission planning a lot easier. You could land near Apollo 11 on the 70th anniversary if you wanted to. It is no harder (or easier) from NRHO than the poles or any other landing site.

To be clear these nuanced challenges mostly apply to the staging point for a crewed mission. If you are fine with adding 15+ day loiter time you can drop heavy cargo on the south pole by going LLO quite cheaply. If it is an expendable cargo lander efficiency doesn't really matter because it is a one way trip so Direct LLO without a loiter becomes viable.

The reality though is it is complicated and it depends on exactly what mission, to exactly where, how long you are willing to loiter, is the lander reusable and is it crewed. Another wrinkle is if it is crewed are the crew in their own vehicle or pushed there by the tanker. If the crew is riding on the tanker than fast insertion is required which means your crew made the thousands of tons of prop more expensive as well. Likely to the dismay of people in NASA doing this kind of analysis the public discourse though has largely been "NRHO is stupid derp derp derp".

Ajax81611 Wise, Aged Ars Veteran
5y
166
Subscriptor
NASA missed a huge soft drink sponsorship opportunity here by not naming it the Perfect Elliptical Polar Stable Insertion with Coplanar Line of Apsides.

Statistical Ars Legatus Legionis
15y
54,490
michaeltherobot said:
You clearly know what you are talking about, so could you ELI5 why polar LLO costs more than equatorial LLO? My intuition that they are the same comes from KSP, in which, soon after leaving Earth orbit, you plan a miniscule burn to adjust lunar insertion from coming around the side to coming over the top.

Of course, in both those cases I then have to decelerate hard at perilune to be captured. Perhaps the flight paths NASA is considering have some way to save dV vs my hard deceleration, which don't work for polar orbits?

The added cost comes from the plane change and plane change at high velocity (low orbit) are expensive. You CAN do something similar to what you describe it just takes longer potentially much longer. The higher the perilune the cheaper the plane change becomes but the longer it takes to reach the perilune. You drop yourself into a highly elliptical orbit around the moon at the same plane as the initial orbit. You then ride up to the perlune, raise the plane to 90 degrees and lower the perilune to circular (decelerate hard).

NASA wouldn't consider doing a plane change in Earth orbit because then you can have a free return trajectory which is a risk reduction factor.

So the tradeoff of DeltaV vs time.

Compare this map to the one in the previous post.

https://arstechnica.com/civis/attachments/1772816223709-png.129833/
1772816223709.png

Significant cheaper but it adds a 3.5 day loiter riding up to the vey high perilune to become as cheap as NRHO (including the transit). To have insertion and exit cost that are 2x this you would need the same loiter on the way back. In KSP things like mission duration are quite cheap and excessive risk doesn't matter but yeah same basic concept and math.

To be clear this is really only an issue for an occupied crew vehicle. If you add a 15 day loiter then the phase change becomes essentially free. For prestaging the lander or the tanker to refuel it after a sortie neither would be harmed by a 30 day longer mission. So if LLO was used as a staging point, which I don't think it will, then there would be mission choices by SpaceX and BO on how much LLO loiter vs round trip DeltaV for sending that tanker to meet lander with the prop it needs.

Statistical Ars Legatus Legionis
15y
54,490
Polar LLO is really hard to get into. Even with a less dumpy crew vehicle bringing it all the way day to Polar LLO and back is dubious. I know know it runs against the popular trend of everything NASA does is stupid but the math doesn't lie.

I got this some years ago when NASA removed the sensitive restriction. Not sure it is available anymore. NASA is pretty bad about maintaining public access to old reports. It was created in the analysis requirements for Constellation.

A direct LLO requires a huge amount of DeltaV to enter and leave when talking about polar landing sites. This is because you need to do an up to 85 degree plane change Exactly how much depends on where exactly you are landing.

https://arstechnica.com/civis/attachments/1772812012884-png.129830/

1772812012884.png

It is at max of 1,313 m/s for the LOI and the south pole landing sites are in those 1,000+ m/s circles. There is a reason Apollo landed in equatorial regions. The LOI for Apollo 11 was 900 m/s.

Now if it takes 1313 m/s to get into LLO then it will take 1313 m/s to get back out. So we are talking 2,626 m/s. Throw in a couple hundred m/s for docking, course corrections (burns are never perfect) and safety margin and 3,000 m/s is a reasonable budget. You can reduce DeltaV somewhat by having a long loiter in LLO which reduces the prohibitive cost of a plane change by coasting up to the apolune (the same way GEO sats coast up to apogee in a GTO orbit but you now largely erased the big advantage of LLO over NRHO in that it is faster for crew missions.

Apollo did consider a polar landing for one of the late Apollo missions but it was canceled due to the higher risk of LoM and LoC. To get the margins needed the Apollo CSM would need to dwell in an intermediate orbit for an extra 2.8 days on the LOI and 1.6 days on the TEI. So an extra four days to the mission timeline. Technically Orion with its 1.3 km/s DeltaV "could" get to Polar LLO but it would require a loiter time of ... 6 days. That is 6 days on the way in and another 6 on the way out. You could make it asymmetrical to reduce risk like Apollo did but it would still be around 12 days loiter on top of 6 days transit on top of 6+ days surface mission.

For reusable landers LLO has another issue. It is so deep in the moon gravity well that while the lander itself uses less propellant you have to bring propellant to the lander. The propellant you bring to the lander requires more DeltaV so that propellant is requiring more propellant. So your lander uses less prop but yout tug/tanker uses more. Total prop usage per mission increases not decreases. A crew landing is essentially all propellant on a first order simplification.

TLDR: NASA knows what they are doing. NRHO got maligned by its association with porkish SLS & Orion (even by me in the past). NRHO is not a terrible orbit for a reusable architecture. It has numerous advantages to include that it is very cold. That is important if you have reusable cryogenic landers trying to minimize boiloff waiting months for crews to arrive. Your lander will point its nose at the sun to reduce thermal load. However in LLO like LEO the moon is a thermal mirror. Thermal load is substantially worse. Using NRHO as a staging point does not require a gateway station.

Even in the analysis above the alternate orbit is all around worse except saving 3% to 6% prop.

On Wednesday, the US Nuclear Regulatory Commission announced that it had issued its first construction approval in nearly a decade. The approval will allow work to begin on a site in Kemmerer, Wyoming, by a company called TerraPower. That company is most widely recognized as being financially backed by Bill Gates, but it’s attempting to build a radically new reactor, one that is sodium-cooled and incorporates energy storage as part of its design.

This doesn’t necessarily mean it will gain approval to operate the reactor, but it’s a critical step for the company.

The TerraPower design, which it calls Natrium and has been developed jointly with GE Hitachi, has several novel features. Probably the most notable of these is the use of liquid sodium for cooling and heat transfer. This allows the primary coolant to circulate at far lower pressure, avoiding any of the challenges posed by the high-pressure water or steam used in water-cooled reactors. But it carries the risk that sodium is highly reactive when exposed to air or water. Natrium is also a fast-neutron reactor, which could allow it to consume some isotopes that would otherwise end up as radioactive waste in more traditional reactor designs.

The reactor is also relatively small compared to most current nuclear plants (345 megawatts versus roughly 1 gigawatt), and incorporates energy storage. Rather than using the heat extracted by the sodium to boil water, the plant will put the heat into a salt-based storage material that can either be used to generate electricity or stored for later use. This will allow the plant to operate around renewable power, which would otherwise undercut it on price. The storage system will also allow it to temporarily output up to 500 MW of electricity. //

1Zach1 Ars Praefectus
8y
3,745
Subscriptor
bumppo said:
It sounds like a mechanism to avoid selling power during the point in the day that solar has driven the price down (potentially into negative territory), while preserving the ability to sell most of that power later.

It would be interesting to know how long the storage is designed to sustain that elevated, up-to-500 MW output.
Here are their plans detailed https://www.terrapower.com/downloads/Natrium-Technology.pdf

Power Output – EnergyStorage System100-500 MWe+ for 5.5+ hours, power ramping at 10% per minute

Regarding NASA’s support for the development of commercial space stations, the bill mandates the following, within specified periods, of passage of the law:

• Within 60 days, publicly release the requirements for commercial space stations in low-Earth orbit
• Within 90 days, release the final “request for proposals” to solicit industry responses
• Within 180 days, enter into contracts with “two or more” commercial providers for such stations
  Cruz is trying to inject urgency into NASA as several private companies—including Axiom Space, Blue Origin, Vast, and Voyager—are finalizing designs for space stations. All have expressed a desire for clarity from NASA on how long the space agency would like its astronauts to stay on board, the types of scientific equipment needed, and much more. These are known as “requirements” in NASA parlance.

What is high or low barometric pressure? Adjusted to sea level, a pressure reading above 30.2 inHg is considered to be high pressure, and below 29.8 inHg is considered low. Most of the time, in human-inhabited places, the barometric pressure will stay close to the normal range (29.8 inHg-30.2 inHg), and will rarely exceed 30.5 inHg or fall below 29.4 inHg. The average barometric pressure is 29.92 inHg (or 1 atmosphere!). In summary:

High Pressure: above 30.2 inHg
Normal Range: 29.8 inHg - 30.2 inHg
Low Pressure: below 29.8 inHg

Use our pipe flow calculator to determine the velocity and flow rate of water that flows by gravity. This tool employs the gravitational form of the Hazen–Williams equation to calculate velocity in a pipe.

OpenAI is in and Anthropic is out as a supplier of AI technology for the US defense department. This news caps a week of bluster by the highest officials in the US government towards some of the wealthiest titans of the big tech industry, and the overhanging specter of the existential risks posed by a new technology powerful enough that the Pentagon claims it is essential to national security. At issue is Anthropic’s insistence that the US Department of Defense (DoD) could not use its models to facilitate “mass surveillance” or “fully autonomous weapons,” provisions the defense secretary Pete Hegseth derided as “woke.” //

Despite the histrionics, this is probably the best outcome for Anthropic—and for the Pentagon. In our free-market economy, both are, and should be, free to sell and buy what they want with whom they want, subject to longstanding federal rules on contracting, acquisitions, and blacklisting. The only factor out of place here are the Pentagon’s vindictive threats.

This page lists devices that are known to support faster than real time backups of MiniDiscs, either via USB to a PC or other means (USB A port, SD card)

Via Web MiniDisc Pro exploits

These (portable) devices support the reverse-engineered functionality in /netmd-exploits/ to export audio from MD via the Web MiniDisc Pro application. Type-S exploits are more developed, reliable, and faster than Type-R exploits.

This is the thermal IR (LWIR) of the total lunar eclipse. A 12" Newtonian has been used as fore-optics. Pseudo color to enhance the details. The pictures shows some younger craters are very bright when the sun is temporarily blocked by the Earth.

MST 20260303 03:35 Partial Lunar Eclipse Thermal Vs. Visible (HDR) Fun to see the dramatic difference on the surface in difference wavelength ranges

Silk Hat and Walking Cane, 3ème mouvement des "Dances in the Canebrakes"
Florence Price