Starship SN15 Flies, Sticks The Landing and Still Standing

This afternoon at 5:24 PM CDT, Starship Prototype SN15 lifted off its test stand into the cloudy skies above Boca Chica, Texas.  Visibility was poor for the entire flight and the normally reliable downlink from the Starship wasn't.  As has always been the case, the flight lasted a few seconds more than six minutes and at 5:30 SN15 landed gracefully and smoothly.

Photo by Jack Beyer, NASASpaceflight.com (as you can read).

You will note that SN15 has two Raptor engines firing; SN10, the only prototype to land until today, landed with one engine.  It landed hard, with obvious damage to some of the legs, resulting in an equally obvious tilt.  It exploded 10 minutes after landing.

Screen capture from NASA Spaceflight.com video

Within the first few seconds after landing, we saw a fire on the concrete at the bottom of the Starship.  Unlike SN10, the fire didn't seem to be under the skirt, and the landing pad area fire control system started drowning the area in water, eventually putting out the fire.  It was probably a minute or two, but seemed like more. 

SpaceX ordinarily covers these launches at their own SpaceX.com/launches website, but it didn't show up for me until after the flight.  Their video isn't that good, it's relying on the same downlink after all, but can be seen here on YouTube, queued up to T-30 seconds before the launch.  SpaceX tends to take those down on their website when another mission takes place, while the YouTube video will be there until SpaceX takes it down.

This is a big day for SpaceX, and even for NASA, who now intends to rely on a close sibling of this vehicle to return to the moon by 2024.  There's more to learn, and I suspect the Raptor engines will be closely examined, perhaps sent to their static testing facility to learn more.  Starships are intended to be extremely reusable, more like airplanes than spacecraft; every flight that successfully lands is a step closer to that goal.  SN16 is either 100% done or close to it over in the shipyard so expect it to be on the test stand, probably within a week. 

It's also a big day for the millions of us who think that not only are spaceships supposed to land standing up and be used over, but they're supposed to be shiny metal, too.

Today happens to be the 60th anniversary of Alan Shepard's first suborbital flight in his Mercury capsule, and America's first manned spaceflight.  All things considered, a bigger anniversary to be noted on this day.

Bank of America Says "Transitory Hyperinflation" Is Coming

Zero Hedge had the story this morning that ought to send chills up all of our spines.  The setting is that the Bank of America has earnings calls with many businesses they work with (as you'd expect), and they note the number of mentions of "concerns about inflation" they hear mentioned.  In their first calls in the previous two weeks, the number of mentions of concerns was up 400% year-over-year (YoY).  That was more than triple the YoY per company so far, the and the biggest jump since BofA started keeping records in 2004.  This week they needed an even bigger chart.  The YoY increase in mentions of "concerns about inflation" reached 800% YoY shattering the week-old record. 

BoA issued an oddly-worded message in a report, which ZeroHedge presented and I'll repeat:

What exactly does transitory hyperinflation mean?  Haven't all episodes of hyperinflation been transitory?  Weimar Republic, Zimbabwe, currently Venezuela... Countries undergoing hyperinflation either restructure their economies (usually several times) to end it, go to war, or they collapse (or some combination of those) right?  In the broader sense, isn't everything that happens in the world transitory?  

I find this an interesting time to post this due to the posts this past weekend by both Bayou Renaissance Man and Area Ocho about inflation showing up everywhere now.  I did a post about inflation being here on April 2nd (although my intent was to ridicule Modern Monetary Theory) and included a graphic from Reddit with a summary of inflation numbers. 

There's advice for dealing with inflation virtually everywhere.  If there's something you need and you believe your income prospects are not likely to be destroyed, it's cheaper now than it will be next week, next month or next year.  Yes, that means stockpile food and supplies while you can.  Yes, that argues to buy anything now, something which can act to further push up prices (not to mention that I don't want to start another run on toilet paper, or any sort of food).  Back in the raging inflation of the '70s, when the dollar was in free fall due to getting off the gold standard for good, it was pretty commonly said that if you needed something you might finance, like a car, not only would the car be more expensive soon, but you'd be paying it off with dollars that were worth less to you if your job held up.  (Many of us remember getting the maximum raises our employers would pay for years in the '70s).  

Is this the final push to destroy the US or just the idiocy of virtually doubling Federal Spending and going to extremely deep deficits?  Maybe it's just that the economics of the last four thousand years are more right and Modern Monetary Theory is going to cause a total collapse?  Got me.  From the practical standpoint it just doesn't matter very much.

Just keep an eye out, keep your head on a swivel, and be careful.

NASA Sued Over Awarding Human Landing System Contract to SpaceX

Stop me if you've heard this kind of story about government contracts.  Last Monday, it was announced that Blue Origin was filing a suit against NASA for awarding the Human Landing System contract exclusively to SpaceX.  Seemingly within moments, the other competitor in the three-way decision, Dynetics also announced a lawsuit for not being chosen to develop the HLS. Elon Musk's response on Twitter was quintessentially Elon Musk. 

There are times I think some 13 year old boys are running the engineering at Tesla and SpaceX.  This fits that idea.  On the other hand, he's right.  Neither Blue Origin or Dynetics has launched anything to orbit.  Dynetics is relying totally on subcontractors; Blue Origin is supposedly doing it themselves, with the New Glenn, the only rocket currently able to compete with the Space Launch System for the coveted "Most Delayed" award.

In the world of big government contracts, such suits seem to have become the norm in the last 20 years; maybe farther back.  I've been in companies that get the contract and then have to holdup starting work until the legal actions are resolved. 

That means that NASA is now legally unable to use funds or resources related to its Human Lander System (HLS) program or the $2.9 billion contract it awarded SpaceX on April 16th to develop a variant of Starship to return humanity to the Moon. However, just like SpaceX has already spent a great deal of its own time and money on Starship development and – more recently – a rapid-fire series of launches, the company appears to have no intention of letting sore losers hamper its rocket factory or test campaign.

Don't get me wrong; it's good in principle for the competitors to be able to verify that the contract was awarded in keeping with the rules everyone was working to.  Further, I think the tendency for these contract awards to generate these protest lawsuits is a nature of the relentless push of companies to look good in this quarter's bottom line; after all, since we pay executives in stock options and other things to avoid the "millionaire's tax", it's only a natural (perhaps unintended) consequence that they would seek to optimize the stock options.  The government contracts are so big that they mean lots to the survival of all of the companies.  Eric Ralph at Teslarati notes:

The primary argument is generally shared by both protestors. In essence, Dynetics [p. 23; PDF] and Blue Origin [PDF] believe that it was unfair or improper for NASA to select just a single provider from the three companies or groups that competed. They argue that downselecting to one provider in lieu of budget shortfalls changed the procurement process and competition so much that NASA should have effectively called it quits and restarted the entire five-month process. Blue Origin and Dynetics also both imply that they were somehow blindsided by NASA’s concerns about a Congressional funding shortfall.

Blindsided?  They can't be stupid enough to not know that funding shortfalls are likely in a program that isn't climate change or New Green Deal-related.  At the time of the award, I recall posting that NASA said it needed $3.3 billion in funding for this fiscal year to meet the goal of landing humans on the Moon by 2024. Congress provided just $850 million, and as a result, NASA acknowledged that 2024 was no longer a realistic target.  They would have rather had more than one contractor but couldn't do it on just over 25% of what they needed. 

A commenter over on Teslarati's article posted this visual (actually three or four commenters did):

Left to right, SpaceX, Dynetics, Blue Origin.  The lander on the left was bid at $3 Billion less than the cheaper of the other two. 

Things that make you go, "hmmm."

It might be worth quoting Eric Berger (from Ars Technica) who tweeted, "I’ve been told that Jeff Bezos is livid about this, and views overturning the HLS award as a top priority for Blue Origin."  It kind of feeds the story being circulated that Jeff Bezos has a personal grudge against or rivalry going with Elon Musk. 

A Ham Radio Series 25 – An RF Safety Worksheet

In last week’s post on RF safety,  I mentioned a worksheet that the ARRL provides to help you determine your RF exposure.  http://www.arrl.org/files/file/Technology/tis/info/pdf/rfex1_2.pdf. I thought it would be useful to show the evaluation of my station on one band.  

The worksheet dedicates one page (A) to determining the power at your antenna by looking up the cable you’re using and determining its loss.  As I’ve said before, with a 100 W antenna and some unavoidable losses between the radio and the antenna, the 24.9 MHz (or 12 meter) band is the first place many of us will need to determine exposures.  My antenna is a Log Periodic Dipole Array (often sarcastically referred to as, “an antenna that operates poorly over a wide range of frequencies”) with minimal – but some – antenna gain on 12m.  My cable is RG-213/U, a more recent version of the RG-8/U cables that hams have been using for decades.  Here’s what worksheet A looks like for my station:  

There’s a couple of calculations in there that might be things you don’t think of.  

First, how do I know the loss?  Because RG-213/U is a well established standard cable, I find a datasheet from a reputable manufacturer and find the table of losses vs. frequency they provide.

You can see that they list attenuation at 10 MHz and 50 MHz, not at the 25 MHz I need.  Time for some linear interpolation.

Given those numbers I’ll round up to 0.6 dB loss at 10 MHz and use 1.3 dB at 50, I’ll solve for the slope assuming it’s a straight line between those points, which is going to be close. 

Slope = (1.3 – 0.6) / ( 50-10), which gives and answer of 0.0175 dB/MHz.  That means the loss is that much more 15 MHz higher than the 0.6 dB insertion loss.  That’s found by multiplying 

Loss at 25 MHz = 0.6 + .0175* 15 or 0.863 dB.  

I’ll round that to 0.86 dB.  Notice that the numbers we used to start (1.3 and 0.6 dB) are per hundred feet.  Since my coax is 50 feet, the loss is 0.43 dB. 

Now how to I turn that loss into percentage?  I’m guessing that’s probably a new thing to people.  Remember a dB is a power ratio, where
dB = 10*log (ratio)
is the value in dB and log denotes the base 10 logarithm.  We want to find the ratio that gives a loss: loss means negative dB.  It’s -0.43 dB not +0.43.
(-.43) = 10 log (ratio), so 
(-.43/10) = log (ratio)
10^(-.43/10) = ratio = 0.906 or 90.6% of the power remains.  

Out of 100 Watts, 90.6% or 90.6 W makes it to the antenna.  Note that in step J, they want to solve for the number of watts lost.  That’s (1-.906) or 0.094 times 100 or 9.4 W lost.  

Worksheet B takes this process almost to its conclusion.  It multiplies the powers found at the end of A and then leaves you to find a few more details. 

The Duty Factor is based on recommendations from the ARRL RF Safety page.  It considers digital modes as the worst case, and my mental model for this page is operating the FT8 mode, which has taken the ham radio world by storm.  

This sheet shows my 100% duty factor and 50% transmit time (built into FT8) means I deliver 45.3 W average to the antenna.  By the first table (in the last article) we can see that evaluation is required on 12m if I deliver 75W to the antenna, and I’m delivering 45.3W.  The harder question is in the second table in that post, which has required distances for people to be from the antenna, depending on antenna gain.   

The manufacturer’s website for my antenna has one number for gain, 7.24 dBi.  That’s between the 6 and 9 dB gain entries and the numbers shown are for the number of meters from the antenna people should be excluded.  The right column is for uncontrolled (general population) exposure, the one we should be using for this.  The worst case would be going to the next higher gain and saying people should be 7.5 meters from the antenna or 24.6 feet.  The antenna is at 20 feet above ground, so a 6’ tall person would have to be 20.2 feet from the front of the antenna.  Since that’s inside the fence on my property, I believe that keeps uncontrolled exposure below the limits. 

Antenna gain is a concern of mine because it doesn't mean what people tend to think it means when dealing with powers.  I've seen this misconception with professionals, so I'm sensitive to it.  Antenna gain doesn't mean that if I put 100 Watts into an antenna with a gain of 6 dB (4 times) that I'm getting 400 watts out.  That's impossible.  If I put 100 Watts in, I get 100 watts out.  What antenna gain means is that one antenna puts more power in some direction than another reference antenna, and it does that by taking power from all the other directions and putting it where the antenna is pointed.  That last table looks suspiciously like they're saying there's more power out of the antenna, but there isn't.  It's stronger in one direction, compared to another antenna but that's all.  I'll cut them some slack because this is work in the extreme near field of the antennas and that's absurdly complex to model. 

The War on Meat

While it turns out that the widely reported story that the latest Biden "infrastructure" bill had provisions to limit beef consumption to a few ounces a month was a fake news story tracked to the UK Daily Mail, that's a minor distraction.  There really is an all out war on eating meat, especially beef, which is grounded in nothing but pseudoscience and propagated rumor.  It has been going on for years and if you're like most people, you've probably have heard some of the arguments so long you tend to think they're true. 

We've covered some of this sort of stuff here.  Junk science is a pet peeve of mine and you'll hardly find an area of science more filled with junk than diet recommendations.  I'll link to this piece because it carries a great table of spurious correlations of the kind that show up in what I've called "he-who" studies:  "he who eats (or does) X is more likely to get Y;" that sort of thing.  There's a great deal of desire on the part of many people to know what they should eat.  Simply saying, "eat what your grandparents ate, not industrial foods" which is honestly as a good a recommendation as anything, doesn't get accepted well.  The alternative, real, randomized controlled experiments that would last for decades, is prohibitively expensive, hard to do, and nobody wants to wait.  As we noted while going through my wife's cancer 24 years ago, it takes five years to get five year survival data; extrapolate that to it takes a lifetime to get life extension data. 

The rest of the world does appear to want to institute a carbon tax on meat because of grossly exaggerated figures on the amount of impact animal farming has on methane production.  First off, the methane from cows is 1.8% of the greenhouse gas emissions in the US.  Second off, methane doesn't come from cattle farts, it comes from cattle burps.  I realize that might be a minor distinction, but the EPA, those high priests of junk science, jumped on the "regulate cattle farts" bandwagon under Obama.  The UN claims cattle create 18% of global greenhouse gas emissions - more than comes from transportation - but they're lumping in all livestock, not just cattle, to include poultry, lamb and all sources of meat.  They're also including the effects of animal feed production, feed harvesting, feeding the animals, the farm vehicles that tend to these animals and everything up to the emissions from the slaughterhouse.  A third of that 18% is blamed on deforestation specifically in Brazil.

Both of those summaries are dishonest.  First, it's not fair to blame methane production in chicken farming on cattle farming, and it's unfair to include everything that the goes into food production to just the tailpipe emissions of vehicles rather than the equivalent entire life cycle associated with transportation.  Second, the part about deforestation is dishonest for two reasons; the easiest being that there's no equivalent deforestation in the US, or in other parts of the world.  In the US the story is reforestation.  We have more trees today than a hundred years ago.  The other reason is that not all grassland could be forest and not all forest can convert to grasslands.  There is some relation between the two, but it's not simple subtraction.  Simply, much of the planet can't be dense forest and can only be grassland. 

Chances are, you've heard until you're subconsciously convinced that low fat foods are healthier.  That data was always suspect, but that cynical observation applies that says old science theories don't go away because the weight of evidence pushes them aside; they go away because old scientists who support them die off.  Since about 2000 there have been many good quality meta-analyses of all the studies that have been done before and concluded the evidence is just too weak to matter.  The diet-heart hypothesis that lifetimes of eating fatty foods and having elevated cholesterol levels led to heart attacks has had conflicting data, like that in older adults higher LDL is associated with longer life, long enough for studies to have essentially concluded the diet-heart hypothesis is dead. 

What about vegetarianism?  It's another belief that has far more faith behind it than evidence.  Seven years ago, I ran a review on a book I'd read by health writer Denise Minger, called "Death by Food Pyramid."  Denise was a 17 year old who had thought she should become a raw food vegan but was unaware of the constant effort required to not destroy her health.  Vitamin B12, for example, just doesn't come in plant matter, at least not to any level that eliminates the need for supplementation.  In Denise's case, she simply needed 17 teeth fixed.  At 17, she went to the dentist and after way too many disconcerting "hmm" sounds, heavy sighs, and pokes with pointy metal objects, found she needed to have 17 teeth worked on - coming from never having had dental problems before she became a vegetarian.  In the space of one year. 

In all of these struggles over diet, we have the same conflicts of interest of special interests that we've had with the Covid fiasco.  Everyone pushes to get their favorite industries pushed by the USDA Dietary Guidelines.  The vegetarian movement is largely pushed by the Seventh Day Adventist church, and some influential doctors they've won over to their side, like Dean Ornish, a diet book author and M.D., and Walter Willet, the very influential head of Harvard's School of Public Health.  The lowfat crowd is pushed by the grain and cereal industry.  The push to get people to eat less meat and saturated fat is pushed by the vegetable seed oil industry, which may well be the absolutely worst things in our processed foods. 

Someone who has spent the last several years fighting to get the USDA Dietary Guidelines fixed is Nina Teicholz, who went from being a low-fat, vegetarian food writer to an omnivore heading the Nutrition Coalition, an organization trying to get the dietary guidelines to more honestly assess science that has been pouring in within the last 20 years.  This an hour long, but very worthwhile talk on many of these topics. 

At the risk of overstating the obvious, If a Government Committee Recommends Something, Do The Opposite, as I said here.  If they tell you to limit red meat, maybe you should eat more of it.

Sometime in the Next Year

Everybody knows the story behind the attempt at humor.  It prompted a long research project by Mrs. Graybeard into whether "those" is the proper word or whether it should be "are they menthols?"  And a nearly half hour long attempt on my part to remove the apostrophe in "menthol's."  It's not referring to something in the possessive.  It's not the menthol's cigarettes.  

SLS Core Stage Now In the VAB on the Kennedy Space Center

The SLS core stage was shipped (literally, by barge) from the Stennis Space Center to the Kennedy Space Center here in Florida this week.  The barge arrived in Florida on the 27th, traveling to the turning basin in front of the Vehicle Assembly Building.  Transfer to inside the VAB was accomplished this afternoon.  At this point, it's now being referred to as the core of Artemis 1: the first, unmanned mission the SLS will fly.   

Teams from the center’s Exploration Ground Systems and contractor Jacobs will perform checkouts ahead of integrating the massive rocket stage with the twin solid rocket boosters, Orion spacecraft, and additional flight hardware ahead of the Artemis I launch.

Artemis I will be the first integrated test of SLS and Orion and will pave the way for landing the first woman and first person of color on the lunar surface. It will be a proving ground for deep space exploration, leading the agency’s efforts under the Artemis program for a sustainable presence on the Moon and preparing for human missions to Mars.

As you would imagine, it's not exactly a trivial exercise to handle something massively heavy yet fragile to loads it wasn't designed for, but that's coming very soon as they need to transfer the core stage to a vertical position for the beginning of the integration process.

The twin solid rocket boosters are completely stacked; that was completed in early March.  Despite their similar appearance to the Space Shuttle Solid Rocket Boosters, they're reported to be the largest and most powerful solid rockets ever made.  Each booster produces 3.6 million pounds of thrust.  An important detail to point out is that, like the Shuttle, those SRBs will support the entire weight of the core stage and everything that's mounted to it.

John Honeycutt, the SLS program manager, said, “with the delivery of the SLS core stage for Artemis I, we have all the parts of the rocket at Kennedy for the first Artemis mission.”  NASA is still aiming for a launch before the end of the year, although they'll openly say that's “challenging.”  The original date published was this coming November, but that was before the test window at Stennis ballooned up to nine months.  To have the schedule hammered that badly and not move the launch date out by more than a month would be truly remarkable.  FWIW, I think this goes beyond challenging all the way to improbable.  I wish them luck but I'd be really surprised if this isn't delayed until well into '22.  I think a three month delay into late February/early March would still be remarkably good.

I can't let this column go without noting that part of the quote above made my skin crawl and filled me with dread.  “Artemis I will .... pave the way for landing the first woman and first person of color on the lunar surface.”  So the goal of the Artemis program is to send identity politics into the universe?  If there's anything about humanity that deserves to die off on earth and not spread it's identity politics.  It was bad enough when they said Artemis was to land the first woman and the next man on the moon, but that's apparently too mild today. 

I think I've been clear that I think SLS has been a horrendously bad waste of money.  The decision to kill a program after so much has been spent on it is a tough one for a politician to make.  They're subject to the sunk cost fallacy over things like this.  They have to admit they threw away billions on something like SLS and never got anything for it.  

Farewell and RIP Michael Collins

Since I ran across this meme a couple of years ago, it has come up whenever references to Michael Collins, pilot of the Apollo 11 Command Module, as being the "loneliest man in history" come up.  I think it's sobering to add three words to the meme.  "Michael Collins is the only human, living or dead, in human history not contained in the frame of this picture."

We learned that Michael Collins died earlier today after battling cancer.  He was 90 years old.  

"He spent his final days peacefully, with his family by his side," the family said in a statement. "Mike always faced the challenges of life with grace and humility, and faced this, his final challenge, in the same way. We will miss him terribly."

With Collins' death, only 10 of the 24 humans who have flown into deep space remain alive: Collins' colleague on the Apollo 11 mission, Buzz Aldrin, as well as Bill Anders, Frank Borman, Charlie Duke, Fred Haise, Jim Lovell, Ken Mattingly, Harrison Schmitt, David Scott, and Tom Stafford.

Eric Berger, space columnist at Ars Technica, has a good biography posted.  After some details of his time in NASA, he concludes this way.

After this historic flight, Armstrong became famous as the first human to walk on the Moon. He bore it with dignity and quietly retreated from public life to work as a professor at the University of Cincinnati. He died in 2012 at the age of 82. Aldrin has lived a more public life, battling alcoholism but emerging as a cultural hero and living icon of the Moon program.

By contrast, Collins went on to a career of service, working as director of the National Air and Space Museum as well as other positions. He was a sober and intellectual figure after the Moon landing and was the poet of the mission, writing perhaps the finest astronaut autobiography of the Apollo age, Carrying the Fire: An Astronaut's Journeys. For anyone interested in a true accounting of what life was like as an astronaut (and watching two friends go down to the Moon), this book is essential reading.

Collins retired as an astronaut after the Apollo 11 mission and, in doing so, turned down a chance to go down to the lunar surface himself. According to Slayton, Collins was his first choice to serve as commander of Apollo 17, which would become the final mission to the Moon. This was even before the launch of Apollo 11. Collins replied by thanking Slayton for the offer but said he had grown tired of the grind, and if Apollo 11 went well he was planning to step aside. Collins has now finally found a deserved and eternal rest.

In 1994, Mrs. Graybeard was working as a technician on the Space Shuttle Solid Rocket Boosters up on the Cape, and I was working for Southeast Area Defense Contractor doing radio design.  When July approached, the KSC announced there would be a celebration of the 25th anniversary of Apollo 11, and all three astronauts would be there.  Families were invited.  Somewhere around here I have some photographs I took of Armstrong, Aldrin and Collins.  Of course, we just watched from the crowd, which included some of the people who were working various jobs in support of Apollo 11.   

When I was younger, I used to wonder how Collins had felt about training all his adulthood for the possibility of going to the moon, and then not landing and walking around.  Later, I came to think he was doing his job, just like Neil Armstrong and Buzz Aldin.  His job was an integral part of theirs.  True, he was closer to the moon than billions of people have ever been, he just wasn't touching it.  As Robert E. Lee famously said, “Do your duty in all things. You cannot do more, you should never wish to do less.”  First and foremost, Michael Collins was doing his duty.

Rest in peace Michael Collins.  The world is a better place for you having passed this way.

After Successful Static Test, Elon Says SN15 to Launch “Later This Week”

The headline on Teslarati was "Musk says upgraded SpaceX Starship to launch “later this week” after static fire test" which would imply that they got the results they wanted from last night's static fire.

Starship SN15 static fire completed, preparing for flight later this week

Today, Lab Padre said SpaceX had issued another over-pressure notice.  The road closure was on and off from 12 Noon to 8PM CDT and it was hard to see if they were going to do a static firing until well after 7PM Eastern.  It was 6:48:47 PM CDT and 7:48 here.  

The commentators on the channel said they had looked at different cameras carefully and are convinced this is a single Raptor firing.  The speculate the reason is that yesterday they tested all three engines with the main tanks while this evening's test was to test one engine with the header tanks.  Those are the two small tanks that hold the fuel and oxidizer for landing.  The LOX tank is at the very nose of the Starship while the methane tank is actually inside the main methane tank, much closer to the engines. 

To put it in perspective, serial numbers 8 through 11 flew between December 2020 and April 2021.  All four failed to complete the tricky maneuver of falling belly first, flipping vertically, lighting two engines and coming to a soft landing.  SN10 landed successfully, but it was a hard landing, collapsing legs.  10 minutes later one tank exploded destroying the vehicle. Lifting a good summary from Eric Ralph at Teslarati:

All four failures ultimately had different causes. Starship SN8 lost fuel tank pressure, starving its Raptors and causing a near-total loss of thrust seconds before touchdown. One of SN9’s Raptors failed to ignite for a landing burn, triggering an even more aggressive impact with the ground. Starship SN10 landed in one piece but its lone landing engine underperformed when it began to ingest helium ullage gas – a quick-fix implemented after SN8’s pressurization issue. SN11 exploded almost immediately after attempting to ignite its three engines for landing, failing even earlier than its predecessors.

All four flight tests saw each respective Starship prototypes narrowly miss a fully successful and survivable landing, providing SpaceX a great deal of data and direct experience to improve the rocket’s design and operations with. Two of the four failures – SN9 and SN11 – appear to have been the fault of one or more of Starship’s three Raptor engines. Beginning with Starship SN15, SpaceX has moved to an upgraded iteration of the next-generation engine, raising hopes that whatever changes the company has implemented will substantially improve reliability and thus the odds of a successful high-altitude launch and landing test.

What does "later this week" mean?  Weather-wise, it looks like Thursday might be the best day, by the Weather Underground forecast.  Friday looks to be cloudy all day with some thunderstorms around all day.  Thursday looks to have lower chance of rain, and clouds clearing out by the late afternoon to evening. 

Monday Got Away From Me

I started down the road on a post but it's just not writing itself.  

Six years ago, I had called Obama's EPA the High Priests of Junk Science.  Biden's EPA - or whoever is driving this driving this New Green Deal agenda is even worse.  Stuff like saying they're going to force us to eat no more than four pounds of beef a year.  I've met people who will eat four pounds in no more than two days.  Their health deteriorates if they don't.  If the administration's intent is to kill off Americans, like we just talked about, that's the only thing that makes sense.

Well, at least we got to see a static firing of SN15 this afternoon, a minute or three before 6PM EDT.

Licensed Hams - A New Rule on May 3rd

The American Radio Relay League reminds all amateurs that in case you've missed it, the new RF exposure rules take effect on Monday, May 3rd. 

The FCC has announced that rule changes detailed in a lengthy 2019 Report and Order governing RF exposure standards go into effect on May 3, 2021. The new rules do not change existing RF exposure (RFE) limits but do require that stations in all services, including amateur radio, be evaluated against existing limits, unless they are exempted. For stations already in place, that evaluation must be completed by May 3, 2023. After May 3 of this year, any new station, or any existing station modified in a way that's likely to change its RFE profile - such as different antenna or placement or greater power - will need to conduct an evaluation by the date of activation or change.

I did a fairly deep dive into the requirements last May, before I had my Ham Radio Series, so they're not on that separate page, but the first part is "A Little Radio Safety Techno-Geekery", and some examples of how to go about the calculations are in the second part, "A Little More on RF Power Safety and Ham Radio."  Besides my writings, the league itself offers things to help you.

"RF Exposure and You" is available in PDF format for free download from ARRL at,
http://www.arrl.org/files/file/Technology/RFsafetyCommittee/28RFSafety.pdf
ARRL also has an RF Safety page on its website at,
http://www.arrl.org/rf-exposure.
The ARRL also has a worksheet that helps in the process.

Here's the odd part.  There are no instructions that this is to be filed with the FCC or anyone else.  I suppose that means you're expected to do the calculations, and keep them on file in case you're questioned at some point.  I would presume that would be if a neighbor complains you're interfering with their TV or Stereo or other form of entertainment and an investigation is started.  Thankfully, with the switch to HDTV and cable, those complaints seem to be fewer than back with analog TV.  

As the ARRL points out, the major change in the rules is that before now, hams were generally exempt from this requirement.  That exemption goes away.  

There is no preferred format stated for the analysis, but sticking with that ARRL worksheet might be a good thing. 

As a quick review, let's look at table 1 in the first of my two posts.  This shows the power at the antenna that requires analysis:

If you operate a typical, off the shelf ham transmitter/transceiver with 100 Watts output power, you don't have to address any exposure until you get to the 12m band, because there are unavoidable losses between the output of the transmitter and the antenna, and even tenths of a dB loss will get you below the 100 Watts that requires evaluation on 15m.  

The next table in that article tells you the distances (in meters) from an antenna with one of four gains where the power is expected to exceed the FCC power density limits.  Always use the "Unc." column, for uncontrolled exposure - note those are always farther away, which means lower power.  The "Con" column, controlled exposure, is for people working in the industry, expected to be more aware of the need for caution.

Note that you may reduce power by the transmit duty cycle because these are time averaged powers; the chart says 50% and without lots of effort to measure that, it isn't unrealistic.  Even "full power, full time" modes like RTTY (Radio Teletype) don't turn on the transmitter and leave it on for minutes on end.  The league says to use 40% of power for CW, 20% for SSB with no speech processing, 40% for SSB with heavy speech processing,  You should also reduce the power getting to the antenna by the loss in the transmission line to the antenna. 

If I reduce the 100W power to 85% to account for the transmission line (following the example in the second article) that leaves 85 watts at the antenna.  If I reduce that to 30% for the transmitter duty cycle, it's now at 25.5 Watts, far short of the 75 W that requires analysis by the first table.  Notice that each frequency band calculates the powers for four different antenna gains.  In the very simple cases, say your 12m antenna has 3 dB gain.  That means the distance from the antenna where the power exceeds the safety limit is 3.8 meters, or 12-1/2 feet, in the direction the antenna is pointed.  If nobody is closer than 3.8 meters from the antenna, you're good. 

That's even below the power to the antenna that requires analysis for the 10m band.  

I think that between the various resources I've linked to here, both the ARRL's handouts and my articles, you should have what you need to determine how to do the analysis for your station.  As a general approach, there's nothing wrong with making worst case assumptions.  Saying you're delivering the full 100 Watts to the antenna - or a full 100% duty cycle.  That way you know you're always delivering less power to anyone near the antenna and that they're always safer than the limits. 

NASA's Getting What It Wanted - Independent, Reliable Access to Space

As we sit here today, the International Space Station has two American spacecraft docked to it.  The last time two manned, American, spacecraft with two separate crews were in space together was the Gemini 6 and 7 mission in 1965.  Today, the crews of the Crew 1 and Crew 2 missions are sharing the (relatively) spacious inside of the ISS. 

Today, we're three months short of the 10th anniversary of the last flight of a Space Shuttle.   NASA had to rely on the Russians for rides to the ISS; who promptly raised prices once they knew they had a captive audience.  Yesterday, SpaceX launched the Crew 2 mission at 5:49 AM local time.  It was the third manned mission that they've launched in under 11 months.  In itself, that's a healthy launch cadence, but since these missions are for months at a time on the ISS, it's likely they won't need to launch much more frequently.  I bet they could if there was a need.

"It took 10 years to get there, to achieve this bold vision for commercial crew," said NASA's acting administrator, Steve Jurczyk, during a news conference after Friday morning's launch. "It’s been amazing what the team has been able to accomplish."

The "team" is a collaboration between engineers at NASA and SpaceX that have worked to develop and certify the Crew Dragon system for human spaceflight for a fixed price of about $55 million per seat. Since 2017, NASA had been paying Russia more than $80 million for an astronaut to ride into orbit.

As I've mentioned before, I've read that back in 2014 when SpaceX was proposing reusable rockets, it was four years before they actually succeeded at recovering a rocket at sea.  NASA told them, in essence, "don't bid that; it's a pipe dream that'll never happen."  Fast forward to Friday morning and the reused Crew Dragon capsule Endeavor was launched on a reused, recovered booster.  In a moment of candor, Elon Musk showed that the progress in their reusable Falcon 9 system is surprising even him.

After the launch, SpaceX founder and Chief Engineer Elon Musk said he felt increasingly confident in the prospects of developing a reusable launch system. "It’s only recently that I feel like full and rapid reusability can be accomplished," he said. "I wasn’t sure for a long time, but I am now."

With the Falcon 9 and Crew Dragon, SpaceX has gotten mostly there. However, the Falcon 9 rocket's upper stage is expended after a launch, and the Dragon capsules undergo significant refurbishment between flights. Musk sees this launch system as an interim stage to full reuse, and SpaceX is still learning lessons. The company has already flown one of its Falcon 9 first stages nine times and will soon fly it a tenth time. The plan is to push the limits of the Falcon 9 with the company's own Starlink missions, Musk said.

"There doesn’t seem to be any obvious limits to the reusability of the vehicle," he said. "We intend to fly the Falcon 9 rocket until we see some kind of failure."

I've worked on designing radio systems for satellites before and it always amazed me to think that the level of screening, testing and documenting the parts is the most stringent of all components.  Then we'd build most rockets, use once and throw away.  I suspect that they're going to find their Falcon 9 boosters will easily exceed the 10 flight milestone.   

Changing perspective wildly, I was able to watch the launch from my back yard as usual, and we were treated to a gorgeous flight, much like the one I wrote about last June.  It looked like a typical night launch until the two stages poked above the day/night terminator at altitude, and suddenly the whole contrail started glowing a bright, light blue.  When the booster cutoff and was jettisoned, the spreading  contrail from the upper stage glowed and I immediately saw the light pulsing stronger and weaker.  Within a few seconds I realized I was seeing the booster guiding itself toward it's eventual landing using its nitrogen thrusters.  Every time the first stage fired them, a spreading arc of white radiated out of it, in whichever direction, also turning light blue.  I got to see the first entry burn, but the landing burn is below the horizon from here.  Photographer Trevor Mahlmann at Ars Technica caught several great photos. 

Here's what you're looking at.  The lowest bright spot is the second stage on the way to orbit.  The bright spot higher in the frame is the booster.  Below it are two spreading lobes of the bright reflection of its thrusters.  Farther out from booster in the upper right is the spreading arc of a slightly earlier firing of the thrusters. 

Earth Day Addendum for the Climate Change Peeps You Know

We all have those acquaintances or maybe family members that have drunk the Kool-Aid about a Climate Catastrophe. The ones who seriously believe the nonsense that it's a critical, problem and the world is going to end in 10 years or whatever we're down to.  Admittedly, most True Believers aren't going to believe what I'm going to show you.  There might, however, be people you talk with who are more data-driven and this will be like putting a pebble in their mental shoe.  They'll have to pay attention to it.

This graphic is from Dr. Roy Spencer, posted at Watts Up With That and at his own blog.  For those who don't know Dr. Spencer, here's his bio page.  What this shows is the predicted sea surface temperature trends predicted by 13 different CMIP6 climate models that were run 68 different times.  Those are plots in the various colors, behind the bolder, black line.  The black line is 42 years of measured data from the National Oceanographic and Atmospheric Administration (NOAA).  Clearly, for most of the plots, starting around 1992, the CMIP6 models dramatically over predict the temperature rise.

If you're not familiar with this sort of plot, the Y-axis is the temperature anomaly, stated as the difference between the 1979-1983 average and the measured or predicted data, plotted per year.  Dr. Spencer concludes that the real warming is half of the model predictions, but the model predictions are spread out over a wide band. The latest observation (right end of the black curve) is approximately 0.3C warmer than the 1979 start of these series, while the predictions range from one lower than the measured temperature at 0.1C to 1.5C higher. 

Dr. Spencer is a reasonable scientist, he admits there are things he doesn't know and more.

A related issue is how much the deep oceans are warming. As I have mentioned before, the (inarguable) energy imbalance associated with deep-ocean warming in recent decades is only about 1 part (less than 1 Watt per sq. m) in 300 of the natural energy flows in the climate system.

This is a very tiny energy imbalance in the climate system. We know NONE of the natural energy flows to that level of accuracy.

What that means is that global warming could be mostly natural, and we would not even know it.

I’m not claiming that is the case. I am merely pointing out the level of faith that is involved in the adjustments made to climate models, which necessarily produce warming due to increasing CO2 because those models simply assume that there is no other source of warming.

That's the big issue we're facing: the reliance on models that don't match measured data and a reluctance to actually do the work to test a model.  The data is often hard to measure and truly global.  Just what does global average temperature even mean and how can it possibly be measured with the accuracy? 

Last words to Dr. Spencer:

Why does it matter?

It matters because there is no Climate Crisis. There is no Climate Emergency.

Yes, irregular warming is occurring. Yes, it is at least partly due to human greenhouse gas emissions. But seldom are the benefits of a somewhat warmer climate system mentioned, or the benefits of more CO2 in the atmosphere (which is required for life on Earth to exist).

There's no reason to spend trillions of dollars on the climate.  That will create real suffering and buy nothing good.

Earth Day 2021

As befitting the environmental movement, my tribute to Earth Day is both late and nearly 50% recycled.  The only way it could fit the environmental movement better would be if everything I said was factually wrong.  No can do.  It wouldn't be me. 

Earth Day, as most of you know, is a holiday made up in the late 1960s at the start of the national environmental movement.  Ira Einhorn is one of the main founders of Earth Day, if not the guy who started it.  Ira practiced what he preached: he murdered his girlfriend (less stress on the planet) and composted her body in his closet.  (Hey - reduce, re-use, recycle!)

You won't find Ira Einhorn's name listed in any of the Earth Day promotional literature, as the organizers have taken great pains to distance themselves from this man, at least since he became better known for composting his girlfriend in a trunk in his closet for a couple of years in the late 1970s.

I was a science geek in high school in 1970, the first Earth Day, and indoctrinated into the liberal crap of the day.  Who can forget the commercial with the crying Indian ("Iron Eyes Cody", who - BTW - was Italian, not Native American) looking at the spoiled earth?  Caught up in the spirit of the day, we went looking for pollution, and tested a local canal for coliform bacteria.   

The movement led to the creation of the Environmental Protection Agency, probably the best example of an agency that has outlived its usefulness.  Unlike government agencies, manufacturing companies are seriously interested in solving problems.  Quality Engineers, Manufacturing Engineers and many others have settled on the Pareto Principle.

Vilfredo Pareto was an Italian engineer who turned his mathematical skills to economic problems.  What he is best known for is the "80-20 Rule", the observation that 20% of the efforts produces 80% of the results.  Although it's an approximation, the rule is more or less right far more often than it is wrong.  Often called Pareto efficiency or Pareto Optimality, it has appeared in quality control, industrial engineering, and popular books.   

How does this relate to the environment?  Pareto (and most of today's Quality Engineers) would say measure your problems.  Find the 20% of problems that cause 80% of the trouble and work to get rid of them while you let the others sit.  Then you "Lather. Rinse. Repeat."  What tends to happen is that you eliminate, or (at least) reduce the biggest problems and then have another set.  You eventually end up with much fewer problems and production running much smoother.  

If you're a government agency, the last thing you want is to solve problems.  Then you have nothing to do.  This is how you get things like the EPA ruling that Ozone concentrations found naturally in unspoiled national parks are higher than should be allowed. 

Two big problems come to mind.  The first is that reducing legal ozone levels because it's a component of pollution is like reducing legal oxygen levels because it's a component in seawater and we don't want to breathe seawater.  The second is that the current limit is already just about at the  natural background level of ozone.  In most of the country, it's physically impossible to measure the new limits because the natural background is higher than the level they're imposing! 

Today, President Xo announced a goal of cutting CO2 emissions by 50% by 2030 - a mere nine years.  Even more laughable was the talk by Climate Czar John Kerry in which he said even when we get there, "We still have to suck carbon dioxide out of the atmosphere." One would hope he doesn't mean suck all the carbon dioxide out of the atmosphere.  Yeah, it's a trace gas but even third graders know that it feeds all the plants, and that sucking all the CO2 out of the atmosphere is impossible.  Every living creature on the planet will add back CO2 one breath later.  Plants exhale their CO2 at night. 

The 50% goal, though, doesn't mean compared to today, it means compared to 2005.  In my world, when a politician picks a date like that, I automatically think "they're cherry picking the worst possible date," and sure enough this plot from Statista shows that 2005 was about the peak year of CO2 production in the US, pretty much 6000 mmt (million metric tons) of CO2. 

The last point on the plot is 2020, and at 4,571 mmt, we're already down to 76% of the 2005 levels.  

I honestly don't think it's possible at any reasonable cost.  The EPA says the transportation sector of the economy generates 29% of the so-called greenhouse gasses, so shutting down all transportation wouldn't be enough.  That includes not just cars and planes, the typical examples of pollution, but includes shipping goods around the country.  Replacing gasoline or diesel cars with electric just moves the CO2 production to the "electricity" sector - not counting the massive CO2 production in the "commercial" pie slice to manufacture the electric cars.  It would take reductions in all the sectors on this pie chart, and I just don't think it's there to save without invoking "and then something magical happens" - as Kerry pretty much did.

From the US EPA.

ATF Proposed Rulemaking on 80% Firearms Leaked

The Federal Administrative Procedure Act of 1946, require agencies changing Federal laws to go through a process.  That process requires the agency present a Notice of Proposed Rulemaking (NPRM) to anyone interested in the change, allowing 60-90 days for comments.  After some period of reviewing the comments and typically allowing some period for commenters to respond, the agency then announces the ruling and any changes made in a Report and Order.  In today's NSSF Ammoland News, they report on a leaked copy of the draft NPRM for the BATFE's rules for so-called Ghost Guns. The document is on Scribd, can be read from the article or downloaded.

The Ammoland article summarizes it this way:

According to the report, any random part that the user could “readily” convert into a firearm would be subject to ATF regulations. As in the past, the document doesn’t define what the term “readily convertible” means. This term could be that any block of metal could be “readily convertible” into a firearm. In fact, the document shows that the ATF used a court case where it took the user eight hours to covert a kit into a gun. The document does highlight the need for a complete machine shop, and qualified workers to complete a firearm would not fall under the proposed rules.

That last sentence leaves out home hobbyists with a reasonably good shop but with no "qualified workers" working for us, leaving us in limbo.  Many of us could make an AR-15 lower from a hunk of raw aluminum bar, but using metal that's already part way toward a finished receiver, like say, an 80% lower, next year's 50% lower, or a "0%" forging simply means our shops can generate fewer ounces of metal chips and finish faster.  

Inadvertently, the BATFE shows just how small this problem is. 

The document makes claims that in the past four years that so-called “ghost guns” have been used in 325 homicides. Their definition of homicide includes justified killings as in self-defense. It does not separate out murders from the total homicides. Even if all 325 homicides included in the report were murders, this number is incredibly small. There are approximately 17,000 murders per year in the United States and that averages out to 46 murders per day. The reported small number they are trying to tie to so-called “ghost guns” highlights that there is not a problem.

Note that they're claiming 325 homicides in four years.  Out of the 17,000 murders per year, they're worried about 41? 

A website new to me, called The Reload, offers an interesting take that Ammoland doesn't go near.

The document also proposes the creation of a definition for “privately made firearms,” which would apply to any gun without a serial number made by somebody who doesn’t have a federal gun-making license. Making guns at home for personal use with devices like 3D printers will not be affected by the definition. However, any privately made firearm sold to a licensed gun dealer would be required to be permanently marked with a serial number by the dealer before it could be sold.

When I made my AR-15 from an 80% lower, I added a serial number that meant essentially nothing; I just figured it was easier to engrave a number than to explain to a potential Officer Friendly in a traffic stop why my gun didn't have a serial number.

I've downloaded the draft NPRM.  It's likely to change before it's released, and it's 107 pages long so I haven't had the time to read the whole thing yet.  One thing I noticed in the few pages I've read is that they seem to be trying to address that nasty little problem they have that an AR-15 lower doesn't match the legal definition of a receiver they're working to, and has made the BATFE drop cases they've been involved in.  Back to The Reload:

The document also lays out plans to broaden and update the federal definition of firearms receiver to correct a problem with the ATF’s interpretation of the current definition. Courts have begun questioning the ATF’s long-running determination that an AR-15 lower is a receiver despite not including several of the parts required in the current definition. Prosecutors have been forced to drop cases involving the ATF’s determination in recent years.

The ATF admitted in the document that “neither the upper nor the lower portion of a split/multi-piece receiver firearm alone falls within the precise wording of the regulatory definition” but lashed out in the document at the “erroneous district court decisions” that employ a “narrow interpretation” of the definition.

I've got to admit that seeing ATF incensed at courts for reading definitions as they're written brings a little bit of schadenfreude here.

The first video I ever put up on YouTube, one pass around the fire control group pocket in my 80% lower, back in 2010.

The columns are saying that DOJ has until May 8 to publish the NPRM, and then the comment period starts.  It's hard to know just where this is going, but I think that at the very least that building a gun will be made harder.  What they seemed to object to in all their actions against Polymer80 is the convenience factor of the company selling the kit of parts to complete the gun alongside the 80% frame.  Fixtures that help you drill the holes for the trigger and safety, like the one in my video, might be made harder to come by because they add convenience. 

SN15 Static Fire Wednesday Afternoon

Probably.  Road closure tomorrow from 12 to 8 PM CDT. 

As recently as this weekend, SpaceX appeared to have plans to static fire Starship SN15 on Monday and launch the rocket within 24 hours – April 20th (4/20).  For reasons never stated, although three Raptor engines were available to install by the end of last week, one, #54, was sent away for some sort of rework (commenters said to the test facility in McGregor, Texas).  Raptor #54 was then installed overnight during the weekend, but Monday's road closure was used to bring the second ground support tank to the new facility they're building. 

The three engines on the way to being installed the first time - SpacePadreIsle photo.  The engine number (54) is barely legible on the top of the engine bell of the engine on the right, but it's pointed at the other engines, not the direction we can read.  The engines reported to be on SN15 now are 54, 61, and 66.  The new version engines start at 54, so these are all the new ones.

Something changed while I was writing this. According to Michael Baylor of NextSpaceflight.com, there's a TFR for Friday. 

Starship SN15:
- Static fire NET Wednesday (4/21)
- Launch NET Friday (4/23)

We'll know more by the time the road is reopened tomorrow night. 

EDIT 4/21/21 8:00PM EDT:  The road closure morphed into two closures, one around noon CDT and one later in the day.  The first was used to move a big crane to the test area; the second was cancelled. 

The situation seems more fluid than usual. To quote Michael Baylor of NextSpaceflight.com again:

Latest road closures:
   - Transport Thursday morning
   - Brief test Thursday evening
   - Static fire Friday morning
Followed by:
   Starship SN15's test flight is likely not until mid-next week at the earliest. SpaceX really wants to land this thing. Expect risk reduction testing and possibly multiple static fires as they look to give themselves the best possible shot.

Ingenuity Helicopter Flies on Mars

This morning at 3:46AM PDT, JPL received confirmation that the Ingenuity helicopter successfully lifted off of the surface on Mars, climbed to 3 meters (~10 feet), hovered for 30 seconds and then landed.  This marks the first time any spacecraft mankind has sent to another body in the solar system has conducted a powered flight.  The solar-powered helicopter first became airborne at 3:34 a.m. EDT (12:34 a.m. PDT) – 12:33 Local Mean Solar Time (Mars time) – a time the Ingenuity team determined would have optimal energy and flight conditions. It then descended, touching back down on the surface of Mars after logging a total of 39.1 seconds of flight.

“Ingenuity is the latest in a long and storied tradition of NASA projects achieving a space exploration goal once thought impossible,” said acting NASA Administrator Steve Jurczyk. “The X-15 was a pathfinder for the space shuttle. Mars Pathfinder and its Sojourner rover did the same for three generations of Mars rovers. We don’t know exactly where Ingenuity will lead us, but today’s results indicate the sky – at least on Mars – may not be the limit.”

The flight (and all flights of Ingenuity will share this) was autonomous.  It was piloted by onboard guidance, navigation, and control systems running algorithms developed by the team at JPL. Because of the distance from Earth to Mars, the signal takes around 16 minutes to get here and 16 minutes to get back, making any sort of control from Earth impossible.  Like the landing and its "seven minutes of terror" when the flight can't be observed in real time, Ingenuity's 39 second flight couldn't be observed either.  If the helicopter had tried to fly upside down due to a wiring error like last November's Arianespace Vega, they wouldn't know that until the video from the Perseverance rover arrived at JPL.

Now that it has flown, the Ingenuity team has its work cut out for it.  Ingenuity is currently on the 16th sol, or Martian day, of its 30-sol (31-Earth day) flight test window.  Most of the unscheduled delay is due to the software issue encountered last week.  The team will spend the next three days going over all the collected data and come up with a plan for the second flight, currently set for NET April 22nd.  

Final words to MiMi Aung, project manager of the Ingenuity Mars Helicopter at JPL, in a short talk she gave this morning while the team was seeing the results of the years of work for the first time.  

“We have been thinking for so long about having our Wright brothers moment on Mars, and here it is. We will take a moment to celebrate our success and then take a cue from Orville and Wilbur regarding what to do next. History shows they got back to work – to learn as much as they could about their new aircraft – and so will we.”

A Little Shop Talk - 3D Printing Internal Features

Within the last couple of weeks, I decided to look into printing internal threads.  The first thing I found is that most people either use threaded inserts or they'll mold a hex-shaped pocket to hold a standard-sized nut that snaps into the pocket.  Still, there are plastics that can be tapped essentially like we'd tap metal.  If I wanted threaded plastic, I could print a cylinder with high enough fill rate that it comes out essentially solid, drill a hole in it and tap it.  Or I could print a cylinder with a hole the diameter of the drill bit that I'd use to prepare aluminum for tapping.  That would eliminate one manual step; why not go one step farther and print the internal threads?  

Right now, the defaults in my slicer software are to print layers 0.2mm thick (just under 0.008"), so think about what the thread would look like sliced like that.  The print head will be moving in or out with respect to the center with every layer, and it's possible there's a discontinuity - a little skip or jag from layer to layer.  That made me think that it would interesting to test this with a thread that's at least 5 or 6 times the layer thickness.  

I figured I'd try to print a 1/4-20 internal thread.  Each turn is .050 and .008" is a bit less than 1/6 of the pitch.  Then I said, "why not print 6-32 thread, too; it doesn't cost that much more".  The distance between thread peaks is 1/32" or .031, so .008 jumps layer to layer are relatively big - 1/4 of the pitch.  The first two threaded parts I got off the printer acted funny.  The holes looked too small and then a screw wouldn't even start.  Eventually I measured the parts and found they were about 2% too small.

These are the first two pieces before removing from the printer.  If you look into the one on the left, the 1/4-20, you can see what looks like a flat on the side of the hole closest to the camera.  Now strain a little and see the same feature on the right.  Look a little closer at the ends on the print bed and you'll see a rim that's wider than the rest of the piece.  I don't really understand that, but that's secondary to them being the wrong size. 

I've built three CNC systems, two mills and a lathe, and the first step before running a program was to calibrate the systems in the motion controller.  You tell it a calculated number of steps per inch, then test how far it goes by putting a dial indicator on the tool and telling it to go 1.000".  For example, if you use a common 200 step per revolution motor, you combine that with the number of turns of the lead screw to move 1.000"; for the .050 inch per turn lead screws on the Sherline, you multiply 200 steps per turn times 20 turns, to get 4000 steps.  When it doesn't go 1.000", you scale your numbers to make it match.  I can find no way of doing that for the printer, so I scaled up my drawings by 2% and reprinted.

That did it.  When I tap a hole in metal, the last steps I take are to get any metal chips from the threading out, and verify it by cleaning out the threads with a screw.  The two parts were tight, but both of them worked fine after I ran a screw through the length of the part, which removed some plastic slivers from the inside.

The trick to this view is the wider rim is at the top.  I started threading from the top end.  For scale, those cylinders are supposed to be exactly 3/8" OD.  Scaling got them closer. 

The word of the day is calibration.  I never really checked anything I've printed so far, but I've noticed that wider area on the bottom (printer bed) before.  The software equivalent to where I did the steps per inch calibration I was describing above is built into the printer. The wider rim doesn't show up in the Cura slicer software I'm using, so some more troubleshooting of just what's going on here is next on the agenda. 

Oh, and it's worth ending on this note. While these would work as plastic standoffs for something like a circuit board in a home project, and they cost about a penny's worth of filament each, I think it would be a better use of resources to buy a bagful of standoffs from some company.  The place for this might well be replacing a standoff in a vintage piece of gear (radio, audio, video...) that broke.  Then design one to match as best you can.