Starship Getting Ready to Hop

In the two weeks since I last posted about Starship SN4, SpaceX has continued to make progress, steadily checking off one test after another until now they're one set of tests short of waiting for the formality of approval to make the 150 m (~500 foot) hop flight. 

In the two weeks since then, they've done a "wet dress rehearsal" and two short (~3 second) static test firings of the Raptor engine (first and second).  Then they pulled that Raptor engine off SN4 and did another cryo pressure-proof test that was done to higher pressures than the previous test: 7.5 bar (110 psi) versus the 4.9 bar test from two weeks ago. 

Today we learn that they replaced the engine today, with a second Raptor engine, serial number 20, seen here.  Because that's a new Raptor, there will be a first static test of that engine, currently looking like it will be May 13th, with a test window open from 9am to 9pm CDT (UTC-5).  Backup days for road closures and such are the next two days.

What's that up there?  The world's highest thrust per buck rocket engine, being driven down a beach road by a fork lift?  Must be Boca Chica and SpaceX.  That was yesterday morning.  Taking a look at the live video feed just now it seems like the engine has been mounted. 

Final words to Teslarati, with one modification.

If that static fire and included wet dress rehearsal (WDR) is successful, Starship will technically be cleared for flight. The only obvious missing piece is an attitude control system (ACS). Starhopper, for example, used cold nitrogen gas thrusters quite literally taken off of flight-proven Falcon boosters. It remains to be seen if SpaceX will take the same approach with Starship SN4 or if a different kind of ACS thruster is already installed on the rocket and hidden in plain sight. For now, it looks like we won’t have to wait long at all to find out.

Instead of "If that static fire and ..." is successful, I'll say "When that static fire..." is successful.  After watching them for these last several months, they are nothing if not relentless.  If the tests don't go well, they'll keep working until the tests pass.  Starship SN5 is almost ready to roll to a test stand now.  Construction on SN6 has started as well.

Weekend Shop Update

Last time, I showed the piston rod and mentioned it wasn't Done done.  I needed to make a couple of small bearings out of bronze and the piston wrist pin.  I had made the wrist pin but grabbed a piece of the wrong size stock - the only piece of the 5/16 drill rod I had - when it was supposed to be 3/16".  I got started on the bearings and came to the realization I didn't have a reamer for the big one.  It's to be reamed to 0.281, or 9/32".  I ordered that last Sunday from an eBay seller and received it Thursday.

Now for the Ta Da! moment for the connecting rod with the bronze bearings in place.

With the wrist pin alongside.

There's another piece I started and made good progress on, but it's not quite ready for its photographic session yet.  This is a beginner's engine and so a lot of parts are acceptable without touches that might be done on a more advanced engine.  One of these is on the crankshaft.  The shaft itself is called out as just a piece of 5/16" Cold Rolled Steel.  I found a piece of drill rod in that diameter at one of the metal dealers and that became the crankshaft.  The way the end of the crankshaft is drawn, this is unbalanced (left side of this picture shows the end).

I've seen various solutions to this; some guys use the square tab for the top and then go into a semicircle for the bottom.  That seemed like it would be trading one imbalance for another, so when I saw the idea on the right here, I thought I'd opt for that.  It's roughed out on the mill but not ready for prime time.

I spent some time on a problem with my Fogbuster cooling system.  It stopped misting the coolant although the air flow is normal.  I've done a couple of things to try to fix it and haven't gotten anywhere.  I cut out the outline of that sector of circle with no liquid, just the air blowing and while the aluminum chips didn't melt onto the cutter, the metal came out looking like I'm not used to seeing.  Shiny but looking ripply.  Almost as if it had melted and then quickly solidified. Some of the aluminum cut away was still warm when I picked the pieces up after cutting.  I don't think I'll be doing much cutting until I get that fixed.  Maybe some of the smaller parts on the smaller machines. 

Date Set for Next Launch of DOD's X-37B Space Plane

Next Saturday, May 16th, is the next launch of the DOD's X-37B space plane on an Atlas V rocket from Cape Canaveral Space Force Station, according to Space News.

Randy Walden, director of the Air Force Rapid Capabilities Office, said the upcoming X-37B mission will be the first to use a service module to host experiments. The service module is an attachment to the aft of the vehicle and “enables us to continue to expand the capabilities of the spacecraft and host more experiments than any of the previous missions,” he said in a statement.

One of the experimental payloads is FalconSat-8, a small satellite developed by the U.S. Air Force Academy and funded by the Air Force Research Laboratory. The FalconSat-8 will carry five science payloads. There are also two NASA experiments to study the results of radiation and other space effects on a materials sample plate and seeds used to grow food. A U.S. Naval Research Laboratory experiment will transform solar power into radio frequency microwave energy which could then be transmitted to the ground.

Hmm.  The concept of putting enormous photovoltaic panels in space, converting the solar power to microwave energy and beaming it down to huge arrays of antennas on the ground has been out there for at least a couple of decades.  Usually referred to as Space Based Solar Power, it has become a stated goal for Japan, China and Russia.  I used to call it "the Microwave Design Engineers' Full Employment Act." 

There are sound reasons to do that.  First of all, the atmosphere doesn't pass all the energy that solar panels in space would get.  In addition, space-based solar panels aren't subject to the big efficiency killers that ground or roof-mounted panels are affected by: windblown sand and dirt, or bird droppings.  To ensure the power beams are safe enough to walk through or for aircraft to fly through, the power per square meter has to be the levels that safety authorities already approve. Or the system architects have to provide good arguments why it can be higher, presumably by ways of keeping people out of the energy beamed down.

This is the first experiment I've heard of to validate the concept. 

By the way - that second quoted paragraph might well be the most the Air Force has ever said about an X-37B mission, especially in advance of the mission.  The X-37B is the "mini-space shuttle" clone that was developed before the shuttles stopped flying, with its first mission in 2010.  The craft has put in very long duration missions. 

The design and landing profile of the X-37B — weighing about 11,000 pounds and nearly 29-foot long — is similar to NASA’s Space Shuttle but it’s one-fourth the size. The most recent mission OTV 5 was launched Sept. 7, 2017 on a SpaceX Falcon 9 rocket from NASA’s Kennedy Space Center. It landed on October 27, 2019.

X-37B, Boeing photo.

Taking a look at the long range forecast, don't plan a trip to Central Florida to see this launch.   Next Saturday looks to be rainy all day.

No, Governor Fredo, That's Not the Question

I heard New York Governor Andrew Cuomo deliver a soundbite yesterday that nearly made me spit.  When talking about keeping New York in shutdown until some mythical things happen, he's quoted in Reason saying:

"How much is a human life worth?" he asked. "That is the real discussion that no one is admitting, openly or freely. That we should. To me, I say the cost of a human life, a human life is priceless. Period."

No governor Fredo.  At best that's about half of the question.  Maybe it's a quarter of it.

Get this through your thick skull:  No Matter What You Do People Will Die.  Like when you ordered nursing homes to take covid positive patients in and killed more people in nursing homes alone than have died in total in all of my state (Florida)?  Like how 66% of patients with covid in NYC supposedly were isolated and staying at home - if it's even possible in NYC to stay in your apartment and not breathe the air from the whole building.  Or the whole block you're on. 

The big question is whether what you're doing is saving more lives than it's costing.  Add up all the good things you're accomplishing, add up all the bad things you're causing and weigh them against each other.  You can't answer that because you don't know any of those except the death count.  You're looking at one thing and only one thing: the politics of your situation and if you can use that to your advantage.  What a surprise, right?  He's a politician.  That's what they do: they look for advantage and if there isn't advantage they blame someone else.

Oh, but you have models.  Ooooh.  You have computers.  I Don't Give A Shit.  If I had nickle for every time a computer model lied to me, I'd be a millionaire. 

Let me put it this way: how much gets spent on verifying and improving those models every year?  How many independent parties have evaluated them?  Hundreds?  Thousands?  More like two college freshmen?  Have they ever been validated by independent testing or are they like global climate models that are never verified?  If there's no incentive to get models right, by testing them against the real world, finding what doesn't agree, modifying them and retesting, constantly, they won't be right. 

Let me tell you how it works when there are real incentives.  For over 30 years I worked in a specialized engineering field.  Relentlessly ruled by physics, so it should be easy, right?  It's just Maxwell's equations; just run a simulation.   There were two competitors each of whom spent millions of dollars every year improving their models and having independent experts test and certify them.  The modeling systems got better every year and as a result we pushed the envelope.  We designed things that were more advanced and harder to model.  Has anyone ever put that kind of pressure on your models?

Cuomo is applying the evil fallacy that "if it saves one life, it's worth it," but that's only for the sound bites in front of cameras and microphones.  As author Jacob Sullum at Reason puts it:

"A human life is priceless" may sound like a nice sentiment, but its moral implications are grotesque. It requires us to ignore any amount of suffering that's not reflected in mortality statistics, as long as the policy that inflicts it can be expected to prolong even one person's life.

The fallacy implicitly means that you can do anything to someone as long as you don't kill them.  The implications reach a dead end when we have to consider the thorny questions like saving a life of someone today at the expense of denying elective surgeries for the last two months and thereby killing some number of new cancer patients who would have survived if they had gotten their cancers removed before they spread.  That's balancing the probability of saving some number of lives today by increasing the probability of killing some number of other people in the next couple of years.  But some of the people you save today will also die within the next couple of years.  Not so straightforward is it, governor?

Governor Andrew "Fredo" Cuomo at a March press conference.  I only call him Fredo because I understand he hates it.  If that's wrong and I'm only insulting his brother, I'm OK with that.

The Rotating Detonation Rocket Engine

Ordinarily, detonation isn't a really good thing to be have going on in a rocket engine or much of anything in life.  Obvious exceptions for blasting sides off of mountains, mining and military.  There's a difference between explosions and the controlled blast of a rocket engine but the detonation holds out a tantalizing prospect. It appears that the explosion could lower the cost of the engines, make engines simpler, so more reliable, and lower their weights by perhaps 30%.  That in turn would make a launch vehicle's payload that much bigger.

This week's Wired reports on research into Rotating Detonation Engines being carried out at the University of Central Florida.  Coincidentally, UCF is located pretty much due west of the Kennedy Space Center, although closer to Orlando than the KSC.  

It turns out this isn't really a new idea.

Rotating detonation engines, or RDEs, sound like something out of science fiction, but the concept is about as old as the space age itself. In the late 1950s and early '60s, aerospace engineers working on rocket engines envisioned RDEs as a way to turn a problem into a solution. “Sometimes the rocket motors would get a real bad instability and you’d get an explosion,” pioneer Arthur Nicholls recalled in a University of Michigan interview shortly before his death. “Then it led to the idea—well, what if we use that?”

Professor Nicholls noted the problem was an instability in the combustion chamber and saw the potential in creating an annular channel, a ring, in which a continuous shockwave propagated around the ring in a continuous explosion.  He was able to produce working models, but the understanding of the physics behind the behavior was lacking and the experiments were dropped as conventional engines became more successful.

RDEs use fuel and oxidizer, like other liquid fuel engines.  The savings come from the details.  In conventional liquid rocket engines you're familiar with, the fuel and oxidizer are pressurized and fed into the ignition chamber using bulky turbopumps and other complicated machinery. An RDE doesn’t need these pressurization systems, because the shock wave from the detonation provides the pressure.

Fast forward to this century and the idea resurfaced for hypersonic missiles and aircraft in the atmosphere.  Professor Kareem Ahmed, director of the Propulsion and Energy Research Laboratory at UCF, has spent the past few years developing a next-generation rocket engine that uses controlled explosions to boost stuff into space.

In the RDE developed by Ahmed and his colleagues, hydrogen and oxygen are fed into a combustion chamber. A small tube is used to send a shock wave into the chamber, which triggers the detonation. As the pressure wave moves through the chamber, it encounters more hydrogen and oxygen being fed into the front of the engine by dozens of tiny injectors. When the detonation wave hits the fresh fuel and oxidizer, it rapidly raises the temperature and pressure of the gases. This causes them to combust and send a flame shooting out of the rocket engine.

Earlier this month, Ahmed and a team of researchers from the University of Central Florida and the US Air Force published the test results from the first rotating detonation engine to use hydrogen and oxygen for propellant. This chemical cocktail is regularly used to propel the upper stage of a rocket on the final leg of its journey to orbit. But Ahmed says that many engineers believed this chemical mixture was too volatile to be used in a rotating detonation engine. “Hydrogen is a crazy fuel,” he says. “Most believed it wasn’t possible to detonate hydrogen and oxygen, because it would tend to deflagrate like a typical rocket engine, rather than a detonation motor.”

The effort to better understand and model the processes in the engine has been aided by modern technologies being better able to study the process as it's happening.

The number of waves produced by the engine is determined by how much propellant is being pumped into the system. The engine built by Ahmed and his colleagues had five waves, but other RDEs have had up to eight. It’s still unclear how the number of waves affects the performance of the engine, which will require a better understanding of the waves themselves. To study the waves produced by their engine, Ahmed and his colleagues added a chemical tracer into the propellant and filmed the engine using a high-speed camera rolling at over 200,000 frames per second.

The speed of the explosion is "wicked fast"; the wavefront is going around the ring at 4000 miles/hour, and they're concerned about movement of a centimeter.  That takes about 1.4 nanoseconds (billionths of a second). Ultra high-speed cameras are required. 

In 2018, the Air Force Research Laboratory announced a program to develop and fly an RDE that used conventional rocket propellants. The engine developed by Ahmed’s team is a result of that program, and he says the Air Force is aiming for the first flight of an RDE engine by 2025.  As part of that effort, James Koch, an interim postdoctoral researcher in applied mathematics at the University of Washington, began working on simulating the physics in the engines.

To overcome the challenges of working on RDEs, engineers rely on computational fluid dynamics to create detailed simulations of the detonation process. This is the same computing technique also used to design new planes, submarines, and rockets, but modeling a rotating detonation engine pushes a supercomputer to its limits. “It’s a very nitty-gritty, brute force approach,” says Koch. “The Department of Defense has been running simulations on rotating detonation engines that take on the order of three weeks to a month to run on their leading supercomputer.”

Koch was determined to find a better way to model the detonation waves, so he turned to a branch of mathematics called nonlinear waves and pattern dynamics, which uses math to create models that describe how patterns form. When Koch and his colleagues fired up a small rotating detonation engine they built in their lab, Koch found that the fundamental physical processes occurring in the engine could be described with his mathematical models—no supercomputer necessary. “This approach worked really well,” Koch says. “I can run a simulation on my laptop that takes maybe 30 seconds to produce results that are similar to what took the DOD three weeks.”

This combination of bits of progress around the country is re-igniting a lot of interest in RDEs.

RDEs may have a lot more to offer than improved rockets. The US Department of Energy is investing in research on using RDEs for stationary power generation, and companies like General Electric are exploring their application to jet engines. But Ahmed says these systems will first be put to practical use in rockets because there’s so much to gain in reduced weight and fuel efficiency. After 60 years of effort, exploding rocket engines might be just about ready to blast off.

An engine from James Koch/University of Washington.  It's interesting that in the midst of this amazing apparatus, anyone who has changed a spark plug will recognize the spark plug boots on the left.  

The Florida Alligator Rules Apply in South Carolina, Too

Over a year ago, I responded to an email from the Florida Fish and Wildlife Commission about "living with alligators".  One of those laws (from the FWC) was "if you see an alligator keep your distance."  A recent death in South Carolina shows those rules apply there as well.

Cynthia Covert, 58, came to Kiawah Island, a gated community southeast of Charleston, to give the homeowner a manicure Friday.  The homeowner reported that while Ms. Covert was "professional in her salon," but was relaxed and excited at the home, talking about her boyfriend’s visit from Tennessee, and brought a glass of wine with her.  Uh oh.  Alcohol is not usually a good sign in stories like this.

Covert saw the alligator while working on the woman’s porch and when Covert finished she started taking pictures of the alligator, the woman told deputies.

The woman and her husband started screaming for Covert to get away from the alligator because they saw it grab a deer a few days earlier, deputies said.

Covert said “I don’t look like a deer” and reached to touch the alligator when the animal attacked, according to the report.

The husband and a neighbor grabbed a rope and threw it to Covert when she surfaced and stood in the pond. Covert grabbed the rope and said “I guess I wont do this again,” but was suddenly pulled under by the alligator, the police report said.

Her official cause of death was not Covid-19 the alligator's bite injuries (one of her legs was badly mauled) but drowning.  This is how alligators attack; they'll grab a leg and spin.  Worst case (to the gator) is they rip off the leg and get that to eat.  Most of the time they drown the animal and eat the whole thing.

I don't think alligators fall into the "cute and cuddly" category from Disney/Bambi, I just think it's total ignorance of the reality of nature.  She thought it was neat and unusual enough to take pictures of.  Ms. Covert won't be around to learn from her mistake, though.  I don't want to make fun of her, but sometimes a person only gets one chance to not make the mistake.

Another great Robert A. Heinlein quote comes to mind, or a portion of it.  It's from the Notebooks of Lazarus Long.  Heinlein wrote this in the context of space flight and exploration (if I remember the book correctly!) but it applies whenever we interact with nature. 

... stupidity is the only universal capital crime; the sentence is death, there is no appeal and execution is carried out automatically and without pity.

Remember, folks, the alligator has the right of way.  You let go where it wants and leave it the f*** alone.  You get out of its way.  You don't try to feed it, unless you want to be known as "stumpy" for the rest of your life, or "the late..."  There's more at the March '19 post.

SpaceX Capturing the Flag - A Story I've Never Heard

As we go into the final three weeks until SpaceX with NASA astronauts Doug Hurley and Bob Behnken return manned spaceflight to the US, Ars Technica Senior Space Editor Eric Berger presents a story I'd never heard before.

In the middle of the final flight of NASA's space shuttle, President Obama called up to the International Space Station to congratulate the crew on their mission. During the call on July 15, 2011, President Obama referenced a flag the four-person crew of STS-135 had brought with them into orbit.

“I understand Atlantis also brought a unique American flag up to the station, one that was flown on the very first shuttle mission and one that will reside on the ISS until an American commercial space company launches astronauts to the station,” President Obama said.

The commander of the shuttle mission, NASA astronaut Chris Ferguson, replied that he intended to present the flag to the space station's residents before space shuttle Atlantis departed for its return to Earth. “It will hopefully maintain a position of honor until the next vehicle launched from US soil brings US astronauts up to dock with the space station," Ferguson said.

Recognizing the potential for a space race among these commercial companies during his call with the crew of space shuttle Atlantis, the president told Ferguson, “I understand it's going to be sort of a ‘capture the flag’ moment here for commercial spaceflights, so good luck to whoever grabs that flag."
...
Nevertheless, it was SpaceX who seized upon the president's telephone call to the space station. The company's account tweeted, "SpaceX commencing flag capturing sequence." This is known as calling your shot.

It doesn't take much more than bravado to make a call like that; achieving it is quite another thing, and at the time there were four competitors who were interested in capturing that flag.  Boeing, Sierra Nevada Corporation, SpaceX, and Blue Origin all received awards, with Boeing and Sierra Nevada taking the biggest amounts.  A secondary "space race" became reality and, as you know, the final down selection came down to tests between Boeing and SpaceX.  Both SpaceX and Boeing had their problems but SpaceX came out in better shape most recently and has earned the right to go after that flag.

Want a really cool twist to this story?  The pilot of the last shuttle flight was Doug Hurley, who will be the commander for the Crew Dragon Demo 2 mission to the ISS.

NASA astronauts Chris Ferguson (left), STS-135 commander; and Doug Hurley, pilot, at a 2011 news conference.  

Ars asked Hurley on Friday if he remembered the flag. "The plan always was that the first US vehicle to launch from Florida and come to the International Space Station would grab that flag that flew both on STS 1 and STS 135, the first and last flights of the shuttle program," he replied. "I think we will probably grab it, and put it in a safe place while we work on board the space station and then we'll bring it back when we come back this summer."

I had a lot of problems with President Obama and his approach to NASA, such as pushing outreach to Muslim nations.  There was constant struggle between congress and White House but one thing Obama did get right was initial and sustained funding for commercial crewed flight.

To borrow closing words from Eric Berger:

We will be exceedingly disappointed if, upon splashdown of a successful Crew Dragon mission, the SpaceX account fails to tweet, "Completing flag capturing sequence."

Yeah, this flag.

Don't Read This Blog

Instead of reading my ramblings, spend 20 minutes to watch this video from FEE - the Foundation for Economic Education.  For a little back story, this video was supposed to have been posted back on April 2nd.  It was blocked by YouTube and put in purgatory; I presume that's because it heavily uses scenes from Captain America: Civil War and YouTube wanted to ensure Marvel Studios (/Disney) was OK with that.




Or watch it full screen or on YouTube or on the FEE Website.

It's well done.

NASA to Pay Staggering $146 Million Per SLS Booster Engine

I've written a lot about the Space Launch System (SLS) over the years; it's that perpetually late, perpetually over budget system that NASA has been overseeing for about a decade.  The SLS was originally supposed to launch in 2017; right now it looks to be no earlier than 2021.  Interestingly, just the cost of schedule delays is in the vicinity of $8 Billion.  According to ARS Technica in 2018, for just the cost of the delays (for 3 years from 2017 until this year)

NASA could have bought by purchasing Falcon Heavy rockets from SpaceX in 2018, 2019, and 2020. That $7.8 billion equates to 86 launches of the reusable Falcon Heavy or 52 of the expendable version.  

The hits just keep on coming for SLS.  According to Ars Technica on Friday, NASA had recently announced a contract to Aerojet Rocketdyne for 18 additional space shuttle main engines for the SLS rocket. That was at a paltry $100 Million per engine; but as the infomercial guys say, “Wait!  There's more!” 

However, this is not the true price of these engines. NASA has previously given more than $1 billion to Aerojet to "restart" production of the space shuttle-era engines and a contract for six new ones. So, according to the space agency, NASA has spent $3.5 billion for a total of 24 rocket engines. That comes to $146 million per engine. 

Now the Space Shuttle Main Engines (SSME or RS-25s) are really awesome engines.  Always feared to be the weak spot in the shuttle program, they went on to have a flawless history.  

It is true that the shuttle main engine, or RS-25, is the Ferrari of rocket engines. NASA designed these brilliant engines in the 1970s for the space shuttle program, during which they each flew multiple launches. A total of 46 engines were built for the shuttle at an estimated cost of $40 million per engine. But now these formerly reusable engines will be flown a single time on the SLS rocket and then dropped into the ocean.

At the risk of beating the obvious dead horse, $146 million is 3.65 times the cost of the engines when they were being built to be reusable.  Aerojet Rocketdyne is asking that for a use-once-and-throw-away engine.  To borrow a line, "that just don't seem right." 

There are a lot of things one could buy in the aerospace industry for $146 million. One might, for example, buy at least six RD-180 engines from Russia. These engines have more than twice the thrust of a space shuttle main engine. Or, one might go to United Launch Alliance's Rocket Builder website and purchase two basic Atlas V rocket launches. You could buy three "flight-proven" Falcon 9 launches. One might even buy a Falcon Heavy launch, which has two-thirds the lift capacity of the Space Launch System at one-twentieth the price, and you'd still have enough money left over to buy several hundred actual Ferrari sports cars. [Bold added - SiG]

It's hard to come up with more pointed example than this final one from Eric Berger at Ars Technica

Speaking of engines, SpaceX is building the Raptor rocket engine to power its Super Heavy rocket and Starship upper stage. The Raptor has slightly more power at sea level than the RS-25 and is designed for dozens of uses. According to SpaceX founder Elon Musk, it costs less than $1 million to build a Raptor engine. The company has already built a couple dozen of them on its own dime. So there's that.

SpaceX has set a goal for the next version of the Raptor engine of $250 thousand.  The published thrust in a vacuum of the SSME is 512,000 lbs.  The stated thrust of the Raptor v2 is  250 tons, or 500,000 lbs.  I'll go out on a limb and say those ratings could well be the same. 

The SLS core currently at Stennis Space Center in Mississippi awaiting fueling and testing.  The testing was put on hold due to the COVID-19 shutdowns back in March.  The SSMEs, with red protective covers over them, are visible at the bottom.

Weekend Shop Update

I'll do a weekend shop update today, since it all transpired earlier in the week. 

When we last talked, I was just about ready to cut the connecting rod after spending too many hours troubleshooting something that I might have remembered if it hadn't been 10 years since I last had to think about it. Once I got the coordinate offset resolved and verified it with a quick cut in air above the part, it was easy to cut.

You'll note some thin flash metal looking like square tabs on both ends that hadn't been cut off on the final pass.  I fastened the rod down with 10-32 cap screws on top of a 3/16 thick piece of scrap steel and the piece deformed under the clamping pressure.  I didn't worry because my plan was to cut a circular arc around each end and I assumed when I turned the part over, those would get cut away. 

The design called for the bulk of the rod to be thinned by 1/32" on both sides with a nice circular arc around the now thicker ends.  I wrote the G-code to cut the circular arcs around both screws (and the path between them) by hand and tested the code with the software I have for that.  The results were as intended. 

Each smaller grid square is 1/4" on a side, and the green lines show the center of the 1/2" diameter cutter, so 1/4" offset from the part.  The red arrows are drawn in to show the direction of the cut from where the cutter starts.  I can count squares and see the dimensions look right.  So I took it to Mach 3 to do an air cut.  This is what Mach3 thought the motion should look like:

Without the grid squares it's hard to know that the small circle on the left is the right size, but the circle starting on the right (end of the blue line) is very obviously wrong.  It's cut in the wrong direction and way too big. 

The code runs correctly in the testing program but not on Mach3?  Aren't they speaking the same language?  Well, yes and no.  As with the CAM program, Mach3 had a default command I hadn't found.  The code it self is simple.

G03  X2.7190 I0.532

G03 tells it cut a circle counterclockwise, the X coordinate (2.7190) is superfluous here and not even needed, the important part is the I 0.532.  My intent, and the way the software I tested it with understood the instruction was that the center of the circle was 0.532" to the right of the X coordinate,  or X = 3.251, and the diameter was twice 0.532 or 1.064" Mach3, however, has an environment variable telling it any coordinate I give it is absolute; in other words, the center wasn't 0.532" farther right of where the cutter was, it was centered at 0.532.  That meant the circle had to be (2.719 - 0.532) or 2.187" radius or 4.374" diameter.  That kinda looks like what those purple circles could be. 

Once I found that in the Mach3 manual, it was easy to see what was going on and change the code so that it cut properly.  The cutter goes to the right side of the left circle on the X axis and cuts it.  When it's done, the cutter is in the middle of the connecting arm again, so I send it to the right circle starting point.  This thins the bar by 1/32" as well.  Finally the right circle is cut.  Take out the retaining screws, flip the piece - this time attaching it directly to the table - reset the Z zero for the 3/16" lower work piece and run the circle cutting program again.

I spent more time sanding and cleaning up the part than it took do the cutting. 

I have a few small pieces to work on next.  I started today and they're going pretty well if I remember to RTFD (D for Drawing).  I cut one the wrong size already. 

There's a few dicey parts that I've never done anything like before but most look like things I know how to do.  There's at least a full page of parts for a DIY carburetor, but Webster (the guy who designed the engine and gave away the plans) has a drawing note that says (in essence) do yourself a favor and don't build this carburetor; just go buy an RC model car carburetor.  I'll probably take his advice.  I'm told the magic words are “Traxxas 4033 carburetor.”

NASA Downselects to Three Companies to Take Us Back to the Moon

Thursday, NASA announced the selection of three different contractors to begin initial development of lunar landing systems that will take astronauts back to the surface of the Moon by 2024.  The three companies and their approaches are rather different and NASA is betting that between them, in the words of NASA Administrator Jim Bridenstine:

"Between the three contractors I think NASA has everything it needs to be successful for the 2024 landing, and not just that, we have what is necessary for a sustainable lunar presence by 2028," NASA Administrator Jim Bridenstine told Ars. "We’re thrilled. Each one of these contractors brings not just unique designs, they’re bringing unique histories and unique philosophies toward development. All of that makes NASA better."

Most notable to me is that two out of three of the prime contractors are the “next generation” space contractors.  While several of the subcontractors are familiar names, it's interesting that they're in the sub-tier to these prime contractors.  Boeing was a known bidder on the contract, and as NASA's Chief of Human Spaceflight Ken Bowersox said last month, was not awarded any contract.

The awards, which cover a period of 10 months, were given to the following teams:

• $579 million to the Blue Origin-led "National Team." Blue Origin will serve as the prime contractor, building the Blue Moon lunar lander as the "descent element" of the system, along with program management, systems engineering, and safety and mission assurance. Lockheed Martin will develop a reusable "ascent element" and lead crewed flight operations. Northrop Grumman will build the "transfer element," and Draper will lead descent guidance and provide flight avionics. It will launch on a New Glenn rocket.
• $253 million to a Dynetics-led team. The company's proposal for a lunar lander is non-traditional and includes Sierra Nevada Corporation as a major partner. The ALPACA lander has a pair of drop tanks that are launched separately, which allow the main lander to be reused. These tanks are depleted and then jettisoned during descent. ALPACA could be launched on United Launch Alliance's Vulcan rocket.
• $135 million to SpaceX. The company bid its Super Heavy rocket and Starship to carry humans to the Moon. The benefit of Starship is that if the vehicle is successful, it would offer NASA a low-cost, reusable solution for its needs.

From this cheap seat, I see Blue Origin and SpaceX as kind of opposite companies in an important way.  Blue Origin has yet to launch anything into orbit, instead working on developing engines, this moon lander, and plans for migrating people to colonies in Space.  They've developed and tested the New Glenn booster but have only done suborbital hops.  SpaceX, by contrast, planned to be in the launch business since the first days of the Falcon 1 just under 12 years ago.  Today, the Falcon 9 is the most experienced booster in the US.  Dynetics is a new one on me, and while they appear to be a Defense sector contractor, they have a Space Solutions webpage featuring several projects, not one of which has flown.

Getting back to the main story, NASA hasn't selected a final architecture for the first human landing mission of the Artemis Program and won't choose one until this 10 month study contract period is over.  For the rest of this year, NASA will assess the technical readiness of the various approaches to deliver both a lander to lunar orbit and the lander technology itself.

NASA is taking a two-pronged approach toward the Artemis program. The agency has a clear mandate from the White House to land humans on the Moon by 2024. This has been criticized by some as a "political" date, but supporters of the fast timeline say it has injected needed urgency into the program. At the same time, NASA also wants to avoid the pitfalls of the Apollo Program—which flew six missions to the Moon and then ended due to high costs—by designing Artemis to be sustainable for the long term.

In this scenario, SpaceX appears to be the wildcard - note they were awarded the least of the three, by a huge margin.  They didn't bid flights on the well-established Falcon Heavy, they bid Starship, which hasn't actually flown at all (nor has the New Glenn or ULA's Vulcan).  Administrator Bridenstine said they couldn't afford to overlook the possibility that Starship will be ready in time.

"SpaceX is really good at flying and testing—and failing and fixing," he said. "People are going to look at this and say, 'My goodness, we just saw Starship blow up again. Why are you giving them a contract?' The answer is because SpaceX is really good at iteratively testing and fixing. This is not new to them. They have a design here that, if successful, is going to be transformational. It’s going to drive down costs and it’s going to increase access, and it’s going to enable commercial activities that historically we’ve only dreamed about. I fully believe that Elon Musk is going to be successful. He is focused like a laser on these activities."

All three lunar landers: from left to right, Blue Origin's Integrated Lander, Dynetics ALPACA Lunar Lander, SpaceX's Starship lander.  All three listed as NASA images.

FCC More Than Doubles WiFi Bandwidth Available for WiFi 6

If WiFi scares you, forget 5G cellular that's still years away, a new generation of WiFi is coming and will be here years sooner than 5G.  According to the Microwaves & RF trade magazine daily email news:

The Federal Communications Commission (FCC) has adopted rules that make 1200 MHz of spectrum in the 6-GHz band (5.925–7.125 GHz) available for unlicensed use. These new rules will usher in Wi-Fi 6, the next generation of Wi-Fi, and play a major role in the growth of the Internet of Things. Wi-Fi 6 will be over 2.5X faster than the current standard and deliver improved performance. Opening the 6-GHz band for unlicensed use will also increase the amount of spectrum available for Wi-Fi by nearly a factor of five and help improve rural connectivity.

Current WiFi activity, WiFi 5, as most of you know, is located in two frequency bands separated by a factor of (a bit over) 2.  The first, and still most widely used band is at 2.4 GHz, stretching from 2.4 to 2.5 GHz - 100 MHz of allocated channels.  The problem with that band has been that it's very busy with Bluetooth, wireless toll collection and a bunch of other services so data rates can be affected.  The newer and higher frequency band is 5.18 to 5.825 GHz, or almost 810 MHz of allocated channels and over eight times the currently available bandwidth as 2.4 GHz WiFi.  The higher frequency band has much more spectrum than the lower (and first) WiFi band, and can have higher data rate channels, too.

The new allocations from the FCC will extend the 5 GHz band up 7.125 GHz.  Instead of 810 MHz, there will be over 2000 MHz of spectrum, almost 2-1/2 times as much spectrum, allowing higher data rates and relieving the congestion of too many signals in the band.  Since this was only authorized by the FCC this week, I'd expect new WiFi routers that go to 7.125 GHz to start hitting the market by the fall. There's already WiFi 6 out there, but why not wait until you get the wider bandwidth?

The transitions to Working From Home (WFH) brought on by the Kung Flu lock downs have increased WiFi usage and put pressure on the nation's systems.  

The trend toward WFH means an explosion in the need for wireless connectivity, and that means even more reliance on Wi-Fi than ever. According to high-end Wi-Fi provider Plume Design, some 22.6 million people were active online during the workday prior to the coronavirus crisis. Now, about 46.2 million users are flooding the data pipelines.

Many of our devices and routers support the prevalent Wi-Fi 5 standard (a.k.a. “the standard formerly known as 802.11ac” now that the Wi-Fi Alliance has shifted to simply numbering the standards rather than using their unwieldy IEEE monikers; I, for one, applaud the move). But what if Wi-Fi 5’s 3.5-Gb/s maximum data rate, 256-QAM limit on subcarrier modulation, and four spatial streams can’t cut the mustard?

The Wi-Fi standard has already evolved beyond Wi-Fi 5. Wi-Fi 6 is with us and promises to alleviate the growing connectivity logjam. It offers numerous improvements over its processor: With eight spatial streams and 1024-QAM subcarrier modulation, Wi-Fi 6 now sports a maximum data rate of 9.6 Gb/s.

Personally, I think this is a wonderful development and more high speed connectivity is a Good Thing.  There are existing users of that spectrum that's being allocated to WiFi (as there almost always are) but the articles make it sound like the FCC is managing the systems to minimize conflict. 

I'm only being slightly facetious about being afraid of WiFi, I know some people are.  Personally, I'd rather have everything in my house wired for gigabit Ethernet but that's for security, not concern over RF.  Chances are that people afraid of WiFi won't be affected by this because they won't have a WiFi router in their house of any kind!

Taking the Long View

There's a saying that goes, “A society grows great when old men plant trees whose shade they know they shall never sit in.”  I've always taken that to mean when we do things that are for the good of people who come long after us. 

Maybe it's a reach to apply that story here, but Amazon founder Jeff Bezos and MIT Professor Danny Hillis have embarked on project that has an even farther off payoff than planting a tree today.  They've begun construction of a clock that Hillis first conceived of in 1986; it's a clock that will tick just once a year and chime once ever thousand years.  Called The Clock of the Long Now, it's designed to keep time for 10,000 years.  Purely mechanical.  It will be powered by day/night thermal cycles and optomechanically reset daily at solar noon to phase lock the clock to solar time.  Talk about trees whose shade he'll never sit in, Jeff will never even hear this clock chime unless it's in a special qualifications test.

It's safe to say that someone who would fund this has to have money to spare, and while Professor Hillis is a millionaire, the project is being funded by Bezos.  At $42 million, the equivalent of change found between the sofa cushions to the World's Richest Man, the clock is being built on land that Bezos owns in the Sierra Diablo Mountains of west Texas.

How does the clock work? Well, the longness of the time involved is the big engineering challenge. The clock is designed to tick just once a year and chime once per millennium. Experts are blasting rooms out of the interior of the mountain in order to install steampunky piles of gears and flywheels. 

The tweet and video can be viewed here on Twitter.  Jeff has put up a website dedicated to the clock and is soliciting ideas for things it could also do.

If you're puzzled about what could motivate a couple of guys to create a clock intended to keep time for 10,000 years, well, join the club.  The original source I ran across at Popular Mechanics said, “Bezos explained the clock as a way to remind people that the far future not only exists, but will happen to their descendants.”  Wikipedia's article includes this note.

In the words of Stewart Brand, a founding board member of the foundation, "Such a clock, if sufficiently impressive and well-engineered, would embody deep time for people. It should be charismatic to visit, interesting to think about, and famous enough to become iconic in the public discourse. Ideally, it would do for thinking about time what the photographs of Earth from space have done for thinking about the environment. Such icons reframe the way people think."^[2]

They're talking up the clock as if it will be some sort of attraction, but it's also remote and hard to get to.  That implies most people will never be able to ever see the clock in person.

The clock itself, though, seems a lot more like a Howard Hughes-esque whim or a Crazy Horse Memorial kind of distant vision. “Visiting the Clock will take a commitment," the website reads. "The nearest airport is several hours away by car, and the foot trail to the Clock is rugged, rising almost 2,000 feet above the valley floor.” 

The self-righteous, environmentalist-sounding aspect of why they're building the clock makes me want to hate them, but I don't.  As far as I can tell, they're doing it all on their own property with their own money and people can do whatever they want with their own money as long as they don't hurt other people.  It looks to me like another situation where a billionaire creates a bunch of jobs.  He wants something and hires a team to do it. 

TANSTAAFL and TANSTAALWUC

You may know Heinlein's TANSTAAFL - There Ain't No Such Thing As A Free Lunch - but I bet you don't know the second one because I just made it up:  There Ain't No Such Thing As A Law Without Unintended Consequences.  At least the first one is more pronounceable.  (Tahns taffle vs. tahns tahl wook?)

Heinlein's TANSTAAFL is often stated as being roughly equivalent to the second law of thermodynamics.  You can't get something for nothing.  No perpetual motion machines.  In The Moon is a Harsh Mistress, where Heinlein first used this phrase, the protagonist talks about the free lunch in a bar and tells another character to consider hidden costs.  Where I'm going with this is for you, gentle readers, to recognize that everything that our leaders think they're doing with their management or government policies has a cost and if they care at all about whether they're doing more harm than good, they should analyze all of the costs and do a Cost Benefit Analysis.  Often, perhaps usually, many of those costs are hidden or unknown unknowns. 

When they decide that we're going to put the country into shutdown to keep from overwhelming the medical system, they're fooling themselves if they think there are no other costs to putting millions of people out of work.  Further, if the only thing they're tracking is the number of people taking up beds in Intensive Care Units, they're lying to themselves about the epidemic by tracking one cost and ignoring scores of others.  Not only is the medical system not overwhelmed, they're literally laying off, furloughing and otherwise shedding thousands of workers because millions of the so-called elective surgeries aren't getting done.  How many people have had a cancer diagnosis but had their treatment halted because they couldn't get the tumor removed or some other elective procedure?  How many of those people will die because of the delay?  We know by comparing American survival stats to those of the British NHS with its ordinarily much longer waits for that sort of procedure that there will more cancer deaths than usual in the US and our survival rates will look more like theirs.

Dr. Nicole Saphier, a radiologist from Memorial Sloan Kettering Cancer Center and a medical analyst on Fox News put some example numbers out in a tweet recently, picked up at 90 Miles From Tyranny:

Considering how bad every other set of numbers that's been tossed around has been, I'm skeptical of this, too, but it's better than estimating how many cases of an illness we haven't had. 

No policy, no law can save lives.  All that a policy can do is trade one group of lives for another. 

Good policies result in a net positive tradeoff. But we have no idea whether the tradeoff is a net positive until we take a sober look at the cost of saving lives. And we can’t do that until we stop with the “if it saves just one life” nonsense.

TANSTAALWUC.

Starship SN4 Breaks “The Cryo Test Barrier”

Late last night through early this morning, SpaceX Starship prototype Serial Number 4  achieved something the first three serial numbers never did.  It survived a fueling test with liquid nitrogen (in place of methane).

Late on Sunday night, SpaceX completed a critical cryogenic test of a Starship prototype at its launch site in South Texas. The successful test, during which chilled nitrogen was loaded into pressurized fuel tanks, was reported on Twitter by SpaceX founder Elon Musk.

The vehicle, dubbed SN4—which stands for Serial Number 4—was pressurized to 4.9 bar, or 4.9 times the atmospheric pressure at the surface of the Earth. This pressure is not as high as Starship's fuel tanks and plumbing system are designed to withstand, but it is enough for a basic flight.

The test of SN3 failed back on the night of April 3rd, which was explained to have been due to a testing error, specifically loading the liquid nitrogen by volume not weight, if I understood them.  As with SN3, the plan was to run these cryogenic tests, and then strap one of their Raptor engines to the protoype for a static test.  That could happen by this weekend.  Once the static tests pass, there will be a test flight of the vehicle.  No, seriously. 

Should the static fire test be successful, Musk has said the SN4 vehicle will make a 150-meter "hop" test, much as the "Starhopper" prototype performed in August 2019. The company has yet to receive regulatory approval for this test, so it may not happen for several weeks.

Serial Number 5, well into construction already, has been earmarked for a higher altitude test flight. Musk has said, if all goes well with SN4, the plan is to attach three Raptors to SN5 for a higher flight test later this spring.  How much spring is left?  Seven weeks?

It helps to remember that Starship is just the upper stage for something much, much bigger:  Starship Super Heavy shown here between the Saturn V and a Falcon 9, the Starship Super Heavy's ancestor.  The vehicle was originally named the BFR, which was cleaned up for public consumption by explaining it as Big Falcon Rocket.  Although the corporate website refers to the rocket as Starship and Super Heavy, they also call it the BFR. 

Starship is the "upper stage" of a two-part, fully reusable launch system that SpaceX is developing. The company's goal is for the "Super Heavy" rocket to boost Starship into orbit, where this vehicle can either carry cargo to some destination or carry dozens of passengers.  

I read somewhere recently that Starship is considered much harder to get right than the Super Heavy booster, so that's why all the prototyping to date has been for the upper stage.  I guess SpaceX regards something with liftoff capability along the lines of a Saturn V, but fully reusable instead of three disposable stages, as their expertise or knowledge base, something they have a pretty good idea of how to do.  I expect their development will continue being fun to watch.

Sunday Shop Update

It's been a couple of weeks since I updated progress on my Webster internal combustion engine, because I had a side project that ended up taking time away from it. 

I'm working on the piston connecting rod.  Needlessly fancy, but guys who make things like this engine like to do needlessly fancy parts (as a rash generalization) so I'm going to try to capture the details.  This is the Conn Rod:

It could be the same thickness for the entire part, but the guy takes 5/16 thick stock and thins it out by 1/32" on both sides.  Plus, he leaves the round shape of the portion that holds the bearings.  Both of the circular openings on both ends get some bearing bronze inserts.  I had to buy a foot of bearing bronze to cut two pieces that are 5/16" long.  It's a lifetime supply.  Anybody that makes anything, from woodworking to electronics projects to robots to mechanical projects knows the hassles of minimum order quantities. 

My process to make this isn't going to be the way guys do it on a manual mill.  That would entail several setups (I think I see six setups but there might be an easier way).  I'm going to cut the outline under CNC control.  I've put temporary holes for 10-32 screws where the .250 and .375 holes will eventually be and I've screwed a piece of 5/16" stock to a tooling plate to cut out the ends.  I hope to get by with two setups: one for cutting the shape which I'll also use for that 1/32" relief cut, and then flip it over to do the relief cut on the other side.  Finally, I'll drill those holes for the bearings. 

To get the CAM program to work on this, I needed to turn the 2D/DXF drawing that I had into a 3D model and save that as an .STL file (stereolithography - the file format most 3D printers use). 

It took a lot of time to get the tool paths that I want, to cut the outline of the part.  It seems that there was a default setting of the CAM program I use (DeskProto - an old version) that I hadn't gotten set when I installed it on this computer back in December.  It made every X and Y coordinate on the part positive, while I set up my fixture to put (0,0) on the mid-line and on the very left edge of the small bearing holder.  I could change the coordinates of my reference point on the mill's table, but changed the coordinates of the part to just use the drawing. 

A simulation of all of the tool paths looks like this:

It looks different - fatter than the rod itself - because the green lines are offset from the part by 1/4" - the radius of the 1/2" bit I'm going to cut this with. 

I had hoped to have this cut today, but then ran into the problem of, "why aren't the coordinates what I told it they should be?"  Once this is cut, it's still going to be the full 5/16" thick and the Conn Rod's thickness won't be relieved around the bearings and in between the ends.  That's going to be another adventure in making tool paths with the CAM program. 

30 Years of the Hubble Space Telescope

The Hubble Space Telescope, often just called the HST, was deployed 30 years ago today: April 25, 1990.  HST was launched the day before onboard shuttle Discovery, but wasn't fully checked out and declared operational until May 20.  For those of us who routinely criticize the Space Launch System for being behind schedule and over budget, there's this gem to consider (also from Wikipedia):

From its original total cost estimate of about US$400 million, the telescope cost about US$4.7 billion by the time of its launch. Hubble's cumulative costs were estimated to be about US$10 billion in 2010, twenty years after launch.^[58]

Gee, just short of 12x the original cost estimate.  NASA has a webpage dedicated to the telescope filled with all sorts of eye-popping pictures.

Probably the thing that the HST is best known for is having a defective primary mirror.  HST's optical design is a type of a Cassegrain reflector called a Ritchey-Chrétien.  RCs have become the preferred optical configuration in high end research observatories because they provide a wide photographic field with less optical distortion off axis than others.  There are three or four types of optical Cassegrain reflectors, which have a concave primary (big) mirror and a convex secondary mirror that typically is around 25% to 30% of the diameter of the primary.  In the RC, both mirrors are hyperbolic (a hyperboloid of revolution).

Convex mirrors of all sorts are more difficult to test than concave mirrors, and require another calibrated mirror to test against.  It has become common practice in testing optical systems to develop a test system with its own optical surfaces that need to be certified correct and use that to test the system being built.  According to a report in New Scientist in 1990, the issue with the HST was because the test system was built incorrectly and yet certified.

NASA has established how a mirror aboard its $1.5 billion Hubble Telescope came to be the wrong shape. The agency said last week that errors in a test instrument apparently led Perkin-Elmer, which fabricated the optics, to finish the 2.4-metre primary mirror of the Hubble Space Telescope incorrectly. Tests by NASA earlier this month showed that a lens in the test instrument, called the ‘reflective null corrector’, is about a millimetre askew. Preliminary analysis indicates that an error of this magnitude could cause the spherical aberration that prevents Hubble from focusing sharply.

For reference, 1mm is just over .039 inch.  That's more than 1/32" and thousands of woodworkers could make the fixture to that accuracy.  The surface is being judged compared to wavelengths of light, around 20 millionths of an inch.   Because of this error, Hubble's primary was made flawlessly to the wrong prescription.  It has been said that an amateur with a light bulb and a straight edge - a Foucault tester - could have told them their mirror was wrong.  And that amateur would have been ignored because their instrument wasn't certified.

I've mentioned a couple of times that I've made a few telescope mirrors grinding glass and then building the instruments.  I've done a lot of Foucault tests.  I think I could have told them their mirror was wrong.

Hubble's optical system was corrected by adding more optics; a package called COSTAR, The Corrective Optics Space Telescope Axial Replacement.  You can be sure it would have produced better images without the additional optics of COSTAR but they made the best of a bad situation.
 

Musk Posts Explanation of March Engine Failure

On Wednesday, before the successful SpaceX Starlink mission, Elon Musk replied to a question on Twitter about what caused the engine failure in the previous Starlink mission, the one that caused the loss of a booster on its fifth flight back on March 8th.

When another Twitter user asked what a "dead leg" is, a third user, David Urry, posted this diagram to explain it, after saying:

My best guess on what the heck Elon's talking about:

1. Must wash out engine with alcohol between uses.
2. Gravity must have defeated getting it all cleared out.
3. Isopropyl would be ice in liquid O2, must be cause of pressure reading error day before. 

According to this week's Rocket Report on Ars Technica:

A source told Ars that the company has already replicated the problem during tests, and that fixing it will require changing some cleaning procedures. This should have no effect on the upcoming Crew Dragon launch.

If you haven't heard the results, Wednesday's Starlink mission was a very successful mission for SpaceX.  First off, all of the Starlink satellites were delivered to orbit as planned.  Next, the booster nailed its landing on the drone ship Of Course I Still Love You.  Third, both fairing halves were recovered; one caught in the net and the other retrieved from the ocean.  These were already re-used fairing halves, opening the possibility of a third flight for the fairings, which will be a first.  Finally, the mission put the Falcon 9 booster ahead of the Atlas V as the most experienced rocket in the US.
The Falcon 9 rocket has now launched 84 times. This surpasses the total flights by United Launch Alliance's Atlas V rocket.

The Atlas V rocket first launched on August 2, 2002—about three months after SpaceX was founded by Elon Musk and two other engineers, Tom Mueller and Chris Thompson. Since then, the Atlas V rocket has flown an average of a little fewer than five missions per year. All were rated as successes.

SpaceX first flew the Falcon 9 rocket on June 4, 2010, from Space Launch Complex 40 in Florida. It has caught up to the Atlas V rocket by flying an increasing cadence of missions from 2017 onward, averaging 17 flights a year over the last three full years. One of SpaceX's launches, CRS-7 in 2015, failed.
...
Perhaps more impressively, the Falcon 9 has assumed the mantle of most-experienced rocket while making multiple revisions to its design and incorporating first-stage reuse. In short, SpaceX increased the flight rate of its rocket even as it has aggressively sought to optimize its performance. The company that was once an upstart now stands among—if not above—the blue bloods of the US launch industry.

It's hard to find fault with that last statement from Eric Berger at ARS.

---

While talking about SpaceX, I should note that serial number 4 of the Starship prototypes was rolled to the test stand at Boca Chica, Texas today.  It's exactly 31 days since they started building SN4 and hours short of 21 days since SN3 failed during it's testing on the night of April 3rd. 

Drone's eye view of SN4 on the pad today.  I prefer this for the sense of scale you get looking down on the cars and trucks as opposed to looking up at the booster from the ground.  If I'm remembering correctly, these Starship prototypes have all been about 100 feet tall and more than 10 feet in diameter.  Photo credit to Elon Musk on Teslarati.

Just a Reminder - Nature Wants You Dead

We had a reminder of that today. 

Actually, Mrs. Graybeard was the target of the reminder today; she went for a walk while I was working on a little project in the radio room. 

She came back in covered in blood and still actively dabbing it away with a blood-soaked tissue.

She had been attacked by a hawk.  It's nesting season around here and the local papers talk about people being dive bombed pretty regularly.  Both of us have heard about this for as long as we can remember, but neither of us had ever been hit by hawk until today.  She says it felt like having a brick dropped on her head and she had no idea what hit her.  She looked around in an instinctive reaction and caught a glimpse of the departing bird.  There are very few coconut trees around here and it's not acorn season so having anything fall out of nowhere and hit your head leads to lots of confusion as you try to figure out what it was.

I helped clean up her head and verified that the claw marks weren't deep enough to require stitches.  Scalp wounds can bleed a lot and she pretty much had blood on every piece of clothing.

I think there will be a visit someplace tomorrow for a tetanus booster. 

And by the most remote of remote coincidences, yesterday while taking the garbage out something made me glance down the side of the house.  Either one of our visitors from 2018 or a relative was on the same side of the house within 3 feet of where that last visitor was standing.  It's in the corner of the lot where trees from the four houses make a fairly dense cover.  As a rough guess, this guy is about 8" tall.

With those talons if he decided to to dive bomb you there would be blood as well.

Solar Cycle Update - We Seem to Have Begun Cycle 25

Long time readers will recall that I used to do a “Solar Update” roughly every six months, but it seems my last regular update was in April of '18.  I kind of got out of the habit when the news every month was roughly the same: we're in an extended minimum.  I did a post on keeping an eye on the solar minimum last December when we were about to set a record for the longest stretch of days without a sunspot - and did a couple of days after that post.

UPDATE: Dec 16 1630 EST:  The record was broken Sunday.  From Spaceweather.com

SUNSPOTS BREAK A SPACE AGE RECORD: Solar Minimum is becoming very deep indeed. Over the weekend, the sun set a Space Age record for spotlessness. So far in 2019, the sun has been without sunspots for more than 270 days, including the last 33 days in a row. Since the Space Age began, no other year has had this many blank suns.

In the last few months, there has been talk among the ham radio propagation watchers that the majority of sunspots since then - around Christmas of '19 - have been new solar cycle spots and that the week around Christmas to New Year's of '20 might end up marking the start of cycle 25.  (New cycle spots are instantly recognizable because they're closer to poles than the solar equator and they have reversed magnetic polarity from those closer to the equator.)

Today we find an article posted on Watts Up With That saying Cycle 25 has just started.  In saying so, the rely on an arcane measurement called the heliospheric current sheet tilt angle, and show that the angle has flattened recently, and they mark the similar points in the previous cycles.

They state that much like “it ain't over until the fat lady sings” ...

The solar cycle isn’t over until the heliospheric current sheet has flattened. The data is provided by the Wilcox Solar Observatory at Stanford University. There were no observations from about 19 December to 5 February; so the values in between have been interpolated from the rotations before and after.

By two measurements; the number of rotations of the sun, (a Carrington rotation or solar day is 27.23 earth days) and by measurements of the 10.7 cm solar flux, they conclude the length of cycle 24 was 11.1 years, which is the average solar cycle length.  Cycle 23 was an outlier with a very extended minimum but this one was average. 

I find it interesting that the planetary A index, a measurement of geomagnetic activity, for cycle 24 continues the trend of being lower than the 20th century “modern warm period.”  This plot shows that from 1932 until 2009 this geomagnetic index never went below values that were on the high side for cycle 24.  I think anyone older than about four could look at this plot and play “one of these things is not like the others.”

A coincidence in timing to be sure, but the ARRL reports that NOAA released their predictions for Cycle 25 and stick with their previous predictions of another cycle like the last one.  

“While this is SWPC’s official Cycle 25 prediction, it’s important to note there is still divergence among various forecasting methods and members of the space weather forecasting community,” Donovan said. “Most forecasts and forecasters agree that the Cycle 25 is likely to be within ±20% of Cycle 24 and is likely to occur between 2024 and 2027.”

To the best of my knowledge, Dr. Valentina Zharkova is still predicting that Cycle 25 will be weaker than the last and that there may be an extended minimum lasting until potentially as late as 2053.  Ish.