Sunday, May 24, 2020

On Memorial Day 2020

Let me join the chorus of folks saying that while you're enjoying your day, be it beach, barbecue, pool or whatever, take a moment to remember or think of and thank those who gave their all in service to us. The ones who don't get to mark the holiday with us.

It's a weird Memorial Day here weather-wise.  The temperature isn't supposed to get over 80 and the National Weather Service is calling for 100% chance of rain, showers, and thunderstorms with 2 to 3 inches of rain possible.  This has been an unusually mild May, with only a day or two hitting 90.  Ordinarily by now, the last week of May, 90 is an everyday thing and the afternoon thunderstorm system has started.

With 100% chance of rain, there will be no barbecue today, and probably not much of anything productive.  Good thing I just put fresh batteries in my UPS for this computer and the house internet/video streaming hub.


I've run this picture more than any other on my blog.  I guess it resonates with me.
In a final act of loyalty, Hawkeye, the dog of slain Navy SEAL U.S. Navy Petty Officer 1st Class Jon T. Tumilson walked up to his fallen master’s casket during the funeral in Rockford, Iowa, and then laid mournfully down beside the body for the rest of the proceedings  [Note: Petty Officer Tumilson was one of the 30 killed in Afghanistan in the shoot down of Extortion 17 which the families blame squarely on the Obama administration - SiG]

 

Saturday, May 23, 2020

A Question for You

A question for you, dear readers. 

My article on interpreting the FCC's RF radiation limits drew several thanks.  It makes me wonder what else you're interested in reading about in the general topic of radio.  Since I made my living in high-performance, high-reliability radio design and I've been a ham for 44 years, that's naturally what I gravitate toward. 

I was thinking about a poll, but I don't even know enough to ask the right questions.

So, comments, please!


 


Mississippi Governor Pwned on Graduation Facebook Live

As high schools across the country are holding virtual graduation ceremonies amid the pandemic, graduating seniors are finding alternative ways to leave a lasting impression on their communities. One such way appears to be pranking the governor into congratulating "Harry Azcrac," class of 2020, in a live broadcast.


He appeared to notice the prank, pausing briefly after reading the name, but continued on without losing his composure.  Later, as the reaction across the Interwebz went into overdrive, he retaliated, tweeting “In 10 minutes we’ll be honoring more graduates on Facebook Live. Maybe even Ben—the pride of the Dover family.”

Oh, we could go for days with these, but it would just be between friends, not on a "serious" livestreaming event.



Friday, May 22, 2020

The Milestones To Wednesday's Manned Launch Keeping Going By

Today was a big day in the preparations for Wednesday's return to manned space flight.  First, today's Flight Readiness Review took place behind closed doors and was declared a success with no issues raised.  Second, the flight-ready Falcon 9 and Crew Dragon capsule underwent a booster static fire test for a few seconds on historic pad 39A.   (That's a surprisingly low quality 5:38 long video that I set to start at 2:45 and the static fire is about 3:10)  The launch vehicle was rolled to the pad yesterday.
On Thursday and Friday, senior managers from NASA, SpaceX, and the space agency's international partners held long meetings to review all of the aspects of an upcoming flight of the Falcon 9 rocket and Crew Dragon spacecraft.

These discussions must have gone well, because on Friday afternoon, NASA officials emerged with a clear message: "There are no significant issues," said NASA Associate Administrator Steve Jurczyk, who led the meetings behind closed doors at Kennedy Space Center. "In the end, it was a very clean review. We are ready to launch."
That article, on Ars Technica, reminds us that it was just over a year ago (Saturday April 20) that the test Crew Dragon capsule was destroyed on the pad when the Super Draco thrusters exploded milliseconds before they were supposed to fire.
Since that time, SpaceX has addressed not only the root cause of that problem but has also overseen a complete redesign of the vehicle's parachute system. The company closed out dozens of other significant issues to reach this point.

NASA's manager of the Commercial Crew Program, Kathy Lueders, acknowledged that the process has been a whirlwind. "Last April, I probably wasn't thinking I was going to be flying in a year, but you know what—you can never sell this NASA and SpaceX team short," she said. "They've always accomplished miracles for me. And I'm very, very proud of them."
It's a busy time until launch and there will be several more milestones to be met before then.
Saturday the crew will conduct a "dry" dress rehearsal in which Hurley and Behnken suit up for launch day, and there will be a Launch Readiness Review meeting on Monday. But the biggest concern is probably weather; there are multiple constraints for the Falcon 9 launch and emergency abort scenarios down range. Florida may see some scattered to widespread showers next week, according to medium-range weather models.

Yet NASA and SpaceX are very close. (NASA Associate Administrator) Jurczyk said Friday it "is hard to believe" we are just five days from launching this crewed mission, and we have to agree. We can't wait.



Thursday, May 21, 2020

The Numbers Don't Lie - NASA's Move to Commercial Space Has Saved Money

Ars Technica's Rocket Report this week includes an excerpt from a longer article with the same title as this blog post.
As part of its initial investment of $396 million into SpaceX, NASA got development of the Cargo Dragon, Falcon 9, and a launch site at Cape Canaveral.
A cost of 50 times more
... At the same time, NASA was developing the Ares I rocket to fly crew into low-Earth orbit. Independent estimates placed the cost of Ares I at about $20 billion. President Obama ultimately canceled the Ares I, projected to have a similar lift capacity to the modern Falcon 9 booster, because it was behind schedule and over budget. The agency, in turn, got a bargain.
The beginnings of the commercial space program goes back nearly 15 years to NASA administrator Michael Griffin, appointed by George W. Bush in 2005.  NASA placed a small bet on the nascent commercial space industry when it sought to diversify its fleet for delivering cargo to the International Space Station.  In 2005, NASA had the space shuttle to ferry supplies, of course, but recognized that the aging system was not going to fly forever.  So NASA administrator Griffin, committed $500 million in seed money for the development of new, privately built spacecraft.
Griffin may not have realized what he had unleashed. The first small “Commercial Orbital Transportation Services” contracts awarded to SpaceX and Orbital Sciences have since expanded into other areas of spaceflight while multiplying in value from hundreds of millions of dollars into billions of dollars. NASA now looks to private companies for not just cargo delivery to orbit but, with Crew Dragon, people. NASA also recently sought commercial services for sending supplies to the Moon and even landing humans there. What began as a pebble tossed into a pond has become a wave.

Critics of this commercial approach certainly remain—it has disrupted the business models of traditional aerospace powers like Boeing and Lockheed Martin, which have long profited from lucrative cost-plus contracts. Some at NASA, too, still don’t trust commercial providers, and they’re especially wary of Elon Musk, the brash founder and chief engineer of SpaceX.
Insiders are still fighting over cost-plus contracts.  In the days before the advances in commercial spaceflight, NASA would specify precisely what they wanted and monitor the contractors with intensive audits, visits and oversight.  If a vehicle ran five years late and doubled its original budget, (cough - SLS - cough) NASA was on the hook for cost overruns. This tended to incentivize programs being late and over budget, but eventually the government got what it wanted. And those big contractors absolutely loved it.  To be fair, when the government is asking some company to do something no one on Earth has ever done, cost-plus is a way of reducing the risk.  The reality is the method becomes harder to justify when a company is building the next generation of something that has been done many times before. 

As the infomercials say, "but that's not all!"  Like every other government agency I'm aware of, there's a conveyor belt of managers going back and forth between the agency and the private sector; between the buyers and the companies they buy from.  That makes it in the interest of some NASA people for the contracts to go late and over budget, too, further incentivizing cost-plus contracts. 

Griffin used the analogy of having a house built to describe his vision for commercial space.
“The contractor builds homes for a living, I’m not creating the contractor’s company. He has to have a company before I will consider allowing him to build a home for me. He builds his homes, and if I like them, I can buy a design that he offers. At different stages of completion he gets money from me if he’s building my home, but he doesn’t get all the money until he has furnished all the product.”
An important point about this analogy that may not be obvious is that if the contractor screws up, it's on his nickel.  That would make the contract for commercial space much more like the "Firm, Fixed Price" model the DOD uses.

Ars presents this table of the highlights:

ProgramCargo DragonCommercial crewConstellation
Type Private, fixed-price Private, fixed-price Government, cost-plus
NASA costs $396 million $5 billion $34.5 billion
Deliverable Cargo Dragon Crew Dragon Ares I rocket

Falcon 9 rocket Starliner spacecraft Orion

Florida launch site Booster integration (costs are estimated)




Results Cargo Dragon went on to fly Crew Dragon to fly in May, Ares I canceled, Orion to be

20 ISS deliveriesStarliner next yearused only in deep space.

Don't make the mistake I made; the entry under Commercial Crew for Starliner isn't the SpaceX Starship we frequently talk about.  Starliner is the Boeing private capsule, which (it seems to me) will be lucky to be flying in a year.  That $5 Billion is the total amount NASA has spent among the various contractors in the running.
Put another way, while SpaceX developed a cargo version of its Dragon spacecraft, the Falcon 9 rocket, and built its launch facilities at Cape Canaveral, the Constellation Program was toiling away on Orion, the Ares I rocket, and ground systems. “We were effectively doing what the Constellation Program was doing with about the same amount of money, total, that they were burning in a single month,” said Mike Horkachuck, the NASA engineer originally assigned to SpaceX for the commercial cargo program. “So that kind of puts it into perspective.”

But that’s just for cargo missions. Now compare the costs for crew transportation. All told, NASA will invest nearly $5 billion in SpaceX and Boeing to bring their Crew Dragon and Starliner systems to the launch pad. Phil McAlister, a NASA manager for commercial space, noted that NASA was on track to spend about six times more for the single Ares I-Orion system than what it ultimately paid for two distinct private spacecraft launched on private rockets.
It's hard to overlook that SpaceX has done much more with much less than the old line contractors have.  For cargo, it has flown more missions for less. As part of the crew development program, NASA paid Boeing about 50 percent more than SpaceX. Despite this, SpaceX completed Crew Dragon about a year ahead of Boeing, which, again, is unlikely to fly a crewed mission before next spring at the earliest.



Wednesday, May 20, 2020

The Test Was Successful - If You Ignore The Fire and Shutdown Afterwards

Yesterday, SpaceX successfully had a static fire test of SN4 at Boca Chica, Texas.  This was at the end of several days of delays and lots of construction being added to the Starship.  Before the end of this video, fire is seen at the bottom of the booster that goes on for quite some time.  Water systems on the test stand spray the fire and eventually put it out, but the results weren't quite clear as of earlier today



Now more than 12 hours after Starship SN4 fired up its new Raptor engine, the ~30m (~100 ft) tall, 9m (~30 ft) wide prototype is apparently trapped with one or both of its propellant tanks still partially filled with liquid (or gaseous) methane and/or oxygen. An initial road closure scheduled from noon to 6pm local quickly came and went and SpaceX and Cameron County Texas have since modified the paperwork, extending the closure a full 24 hours. In other words, SpaceX has reason to believe that Starship SN4 may continue to be unsafe (i.e. pressurized) as many as ~30 hours after it technically completed its third static fire test – extremely unusual, to say the least.

There’s only one obvious conclusion to draw. Whether it was something invisible to the public eye or damage related to the off-nominal fire that burned for some 15 minutes after Raptor shut down, SpaceX appears – to some extent – to have lost control of Starship SN4.
I've tuned into the live feed a few times today, and there's no visible work being done.  The road alongside the test stand is closed (it was opened yesterday a couple of hours after the test) and the info panel says the road is scheduled to stay closed until 8AM (CDT) tomorrow.  There have been no workers to the pad since the incident.
Given that safety is almost certainly the priority, chances are that some combination of fairly mild hardware failure and telemetry/control loss has left SpaceX with just enough uncertainty that it can’t risk sending technicians to the launch site to inspect the damage and reestablish control. As a result, the only option left is to quite literally sit and wait until it’s once again safe to approach the rocket. Thankfully, at this point, the risk of the mystery problem actually destroying Starship SN4 is very low. If, as it appears, only its methane tank is affected, leaving some unknown quantity of latent liquid methane trapped inside, it’s possible that waiting will actually solve the problem and safe the rocket.

The fact that Starship hasn’t exploded yet strongly implies either that the amount of propellant trapped is minuscule or that the vast majority of SN4’s propellant management systems (including vents) remain functional. Assuming that’s the case, any remaining cryogenic propellant will eventually boil into gas, increasing the pressure inside Starship’s tanks, while those tanks will continue to vent to prevent an explosion or rupture. Eventually, Starship SN4 will be empty once again and SpaceX will be able to approach the rocket to regain control and begin inspections and repairs.
At some point, they're going to have to do something with SN4.  If they can't get to the pad at all for days or a week that throws a big monkey wrench into their operations.  It sounds like SN5 is either ready now, or not far from it, so it's possible that they'll swap the prototypes, but not if they can't work around SN4.  The next few days were supposed to include a hop to 150m (~500 feet) but that's on hold now.  If they were to scrap 4 and go to 5, they'd need to start the entire testing routine over. 

Honestly, I don't see any problem with SN4 that a .308 couldn't solve, from far enough away.  One through hole, get rid of the residual gas (methane or LOX), and weld a patch over the holes. 

In other space news, as I expected, SpaceX cancelled the Starlink mission which had been scheduled for early Tuesday morning and slipped it off until after next Wednesdays' historic Demo 2 mission.  When the stories started Monday morning about fairing recovery ships Ms Tree and Ms Chief were headed for shelter in North Carolina because of Tropical Storm Arthur, it seemed a foregone conclusion the mission would be rescheduled.  The other two ships on the mission, Go Quest and Of Course I Still Love You, stayed offshore and dealt with the seas from the storm.

Preparations continue for Demo 2 next Wednesday afternoon with the crew arriving at the KSC today for final preparations.   
On Thursday, May 21, NASA and SpaceX will conduct a flight readiness review system to evaluate the Crew Dragon and deem it ready for flight. If the vehicle passes that, then on Friday, a static fire test will occur, followed by a crew dress rehearsal. On Monday, NASA will hold its final launch readiness review. If all goes as planned, Bob and Doug will board their spacecraft approximately three hours before launch.

Astronauts Bob Behnken and Doug Hurley (left), NASA Administrator Jim Bridenstine and an unnamed guy.

Liftoff is scheduled for 1633 EDT on Wednesday the 27th.  It has been a lot of years since I've seen one of these for a manned launch.




Tuesday, May 19, 2020

A Little Radio Safety Techno-Geekery

I think everyone who reads here regularly knows that I've written on the topic of RF safety; probably the most in-depth look was a Radio Sunday post last summer.  You'll probably have noticed that I consider RF (Radio Frequency) energy as visible light only lower in energy, because, well, it is!  Sunlight or electrical light, if it's too bright or too powerful, can damage delicate tissues.  Nobody disputes that RF can cause injury from heating, everyone knows we have physical therapy diathermy machines and microwave ovens (systems which depend on exactly the same phenomenon - dielectric heating); it's the "other stuff" that gets blamed on RF, everything from cataracts to hemorrhoids. 

If you're an amateur radio operator, you're required to attest to the safety of your station on your license renewals, and it's typically not even something that needs to be analyzed.  If you run the typical 100 Watt transmitter and like to hang out on 40 or 80 meters, you don't even need to do the simplest analysis.  

The FCC publishes an excellent (and very readable) document with a dense title: “Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields” (pdf warning) and subtitled “Supplement B (Edition 97-01) to OET Bulletin 65 (Edition 97-01).”    Some title, isn't it?  To paraphrase Mark Steyn, it's not written like a refrigerator manual for people who really love refrigerator manuals.  It's well written - but it is kind of dense.   

I thought it would be helpful to reproduce some information out of this.  The first is the power limits for a ham station that don't require any analysis at all.  This is Table 1 in the document.


Reading directly across, say you're running that 100W transceiver on 20m.  Regardless of your antenna, you can't generate enough RF fields in a nearby observer to be even potentially hazardous.  You need to look closer if you're running 225 W PEP into the antenna, which is going to be less than your radio's output because of loss in the cable or switches or anything else the signal goes through.  Notice though that if you run that same radio on 10 meters you need to do some analysis because the limit there is 50 Watts.

Reading farther, though, you see if you're running more than 50 W on any VHF band (6m, 2m and 220MHz in the US), you need to look a little farther.  As the frequency goes up through UHF into the microwaves and higher, those powers go up. 

So what if you want to run full amateur power on HF through 6m, 1500 W PEP?  Then you need to look at these tables. 


This takes you through HF and the next one takes you as high as the FCC document goes. 


The tables all use the same basic approach, so let me grab the top of Table 4b - the 6m (50-54 MHz) section.  There are six entries for six different antenna gains.  There's a couple of ways of expressing antenna gain but these all use dBi; that's the ratio of the power in the forward direction with respect to a theoretical radiator that is equal power in all directions (an isotropic radiator - where the "i" comes from).   It takes a pretty phenomenal antenna to get to the last one at 15 dBi. I'll grab the 9 dBi antenna because it's a good antenna and it's an example.

What the numbers across tell you is the safe distance from the antenna for Controlled access (someone who knows it could be dangerous, like you) and Uncontrolled access.  That would be your neighbors, kids in the street and so on.  If you're running 100W, the closest those uncontrolled people should get is 9 meters (about 30') from the front of the antenna.  If you're running 1500 W, those kids shouldn't be within 28.4m or 93 feet. 

It's important to note that those numbers are for 100% duty cycle: full power, all the time.  Some digital modes put out full power for transmissions that might be 30 seconds out of a minute while conversational exchanges will be less.  It is fair to de-rate those numbers and say that during your contacts you listen about half the time and transmit about half, and that means lower average power. 

Let's say you're pointing your antenna in the direction of some neighbor (unavoidable in the suburbs and many places).  If their house is more than 93 feet from your antenna, they won't be exposed to a level of RF that could be dangerous. 

The same basic analysis approach applies from as low as 160m at 1.8-2.0 MHz to as high as the 23cm ham band at 1240-1300 MHz. 

It's easy to miss an important point here.  These are straight line distances, so if your antenna is up on a tower and the neighbor's house is one story, you calculate the hypotenuse of the triangle from your antenna at (for example) 66 feet and the straight line distance to their house.  If the distance from the front of your antenna to their house is 200 feet and the antenna is 66 feet up the distance you care about is 211 feet.  If your antenna points at the window of a multi-story building, you're back to the 200 feet. 



Monday, May 18, 2020

And the Anti-5G Attacks Spread to the US

Back in early April, I ran a story about attacks on 5G cellular infrastructure in the UK, setting fire to infrastructure and attacking workers who were laying so-called 5G cables.  Since the term 5G describes an over-the-air set of protocols, it may be terribly pedantic, but 5G doesn't exist in cables, just in radio signal over the air.  The cables carry data, just like a Godzillion other cables.  The attackers are attacking people for nothing.

I learned today that the Department of Homeland Security is issuing notices to the industry about attacks on cell towers and telecommunications workers by 5G/coronavirus conspiracy theorists. The DHS warned that there have already been "arson and physical attacks against cell towers in several US states," and warns that more may be coming.  They're advising the wireless infrastructure providers to pay more attention to securing their properties.
The preposterous claim that 5G can spread the coronavirus, either by suppressing the immune system or by directly transmitting the virus over radio waves, led to dozens of tower burnings in the UK and mainland Europe. Now, the DHS "is preparing to advise the US telecom industry on steps it can take to prevent attacks on 5G cell towers following a rash of incidents in Western Europe fueled by the false claim that the technology spreads the pathogen causing COVID-19," The Washington Post reported last week.
Did you catch that they talked about "directly transmitting the virus over radio waves?"  That's physically impossible.  If anyone believes that enough to go damage a cellular tower or hurt a worker, they should do themselves a favor and try to prove it.  If they can demonstrate that it's possible to transmit a virus by radio, they can win a Nobel prize in medicine and get themselves mentioned with greatest scientists of all time.  Plus, they'll never have to work another day in their lives. 

A telecom industry official said that carriers in the US "have seen sporadic attacks on their cell towers that were apparently prompted by COVID-19 disinformation" over the past few weeks, and the DHS said that attacks on cellular infrastructure date back to December of last year.
"since December 2019, unidentified actors conducted at least five arson incidents targeting cell towers in Memphis, Tenn., that resulted in more than $100,000 in damages... Additionally, 14 cell towers in western Tennessee, between February and April, were purposely turned off by way of disabling their electrical breakers."
Considering that 5G doesn't exist anywhere, yet; at least not in the form with millimeter wave systems that seem to cause the most fear, these attacks are particularly stupid.  At best, the widely deployed systems are 4-1/2 G.  The attackers aren't even close to their target.
The warning to law enforcement agencies said that an April 22 Facebook post "encouraged individuals associated with anarchist extremist ideology to commit acts of sabotage by attacking buildings and 5G towers around the world… in furtherance of an 'International Day of Sabotage'" and that videos have been posted online "showing people how to damage or destroy cell towers," according to ABC.

"Violent extremists have drawn from misinformation campaigns online that claim wireless infrastructure is deleterious to human health and helps spread COVID-19, resulting in a global effort by like-minded individuals to share operational guidance and justification for conducting attacks against 5G infrastructure, some of which have already prompted arson and physical attacks against cell towers in several US states," the DHS report said. The DHS report also warned of possible attacks against the electric grid.
The conspiracy theories also hold that the 5G radio waves suppress the immune system.  Again: 5G describes a system for using radio frequencies that have been in use widely for decades.  There is no known mechanism by which radio can suppress the immune system and no known evidence that it has ever happened.  The only linkage between 5G and Covid-19 is the coincidence of 5G starting to be talked about when the virus first got out into the population.

A reader sent me a link to this video about 5G that seems to be technically solid, just not covering everything I'd like to see covered.  On the other hand, if it was everything I'd like covered it would easily be a half hour long.



Sunday, May 17, 2020

Weekend Shop Update

Seriously, I sometimes wonder why do I do these on the weekend?  The days when I could only work in the shop on the weekend are long gone, and I'm out there some amount of time every day.  I guess the reasons are twofold: first, not to overwhelm with every little thing I'm up to all the time, and second, it's the weekend and everybody's pace of posts is down, be it Sunday Music or just lower activity.

First item, the problem I mentioned about my Fogbuster not spraying seems to be resolved. I only ran it for a few minutes, but it behaved more normally in that test than any other time last week.  The problem, as a comment from reader Leigh suggested
Yeah, it sounds like the issue is between the needle and the outlet orifice of the spray head.
and it was.  I had noticed what looked like a line around the tip of the needle valve but assumed that would cause a leak - too much coolant not none.  I chucked the needle valve in the lathe and held a file against the taper briefly, then finished it with 240 grit paper, followed by 320, 500, then finally with Simichrome polish.

Next, I finished the counterweight that I included a drawing of last week.


Those are 1/4 and 5/16" dowel pins in the two holes. They're not a press fit; you can lift the counterweight off them without moving them, if you're careful. 

After that I spent time working on the approach to machine the rocker arm that gets controlled by a cam on that crankshaft.   The drawing looks like this, top view on top, face view on the bottom:


This is to be made from steel, 1018 cold rolled.  I've cut a piece of bar to be the rough it will be machined from.  The top view is a little tricky; it looks like it's 1/4" across and it is - until you get to that 1/4" square tab on the right that adds 1/16" to the width, making it 0.313".  There's not much metal in this whole piece to hold onto while you're milling it. 

The other things I'm working on are some Tee nuts for the small (Sherline) mill, my version of a product made by a company that went out of business,  and a way to make an enclosure for a little ham radio project that doesn't involve hollowing out an aluminum bar and splitting 80% of it between the recycling bin and the vacuum cleaner.




Saturday, May 16, 2020

Weekend Looking Pretty Much Like Expected

This morning's launch attempt for the X-37B was scrubbed, currently rescheduled for tomorrow morning at 9:14 local. 

The possible tropical or sub-tropical storm has developed to be Tropical Depression #1, also pretty much as expected.  I'm a little surprised that Tomorrow morning's 3AM scheduled launch for the SpaceX Starlink mission 8 has been rescheduled for Tuesday morning, according to the local fish wrapper.  As that link says, Tuesday is cutting it close, especially with seas in the category of "partly to completely crappy," which the storm brings.  Booster recovery ship OCISLY was on location waiting for the launch as of this morning.


NOAA/National Hurricane Center graphic.  The "S" just north of the 8 PM Sat spot indicates they expect it to be a named storm by the next forecast.  That will be Albert.

A tropical storm before the start of the season isn't unusual. As a rough guess, I'd say it happens every other year; maybe every third year.  The one thing I'm a little surprised at is that it happens while we're having the mildest May I can recall. We're coming out of a 10 day period where a solid week never made over 80 degrees for the high. The forecast for Memorial Day is for a high of 84; granted that's a 10-day forecast which isn't the most accurate, but I recall a lot Mays that had afternoons in the 90s by about the end of the first week, and the every-afternoon-quitting-time thunderstorms starting by then or the next week. As it is, the only day in the Forecast with a high touching 90 might be Monday (day after tomorrow), although the official forecast is 89. 



Friday, May 15, 2020

Some Virus Stories That Have Grabbed My Attention

Over the past month, as the nation struggles with trying to resume some degree of normalcy and apparently is fighting off tyrannical state authorities without actually, so to speak, fighting those state authorities, a handful of stories have caught my eye and got stuck in a folder full of stories.  I thought I'd post about that here, but I could put dozens of pictures in this post and take dozens of screens to tell the story.  After some consideration, I thought I'd offer a link and a brief explanation. 

Bear in mind, I'm an advocate of the idea that the important things in any learning situation are the things that aren't expected.   It's often stated as “the most important phrase in a scientific investigation is rarely, 'Eureka! I've found it!!'; it's usually 'that's funny'.”  As one professor told me years ago, if you're not surprised, you're not learning anything new.

To begin with, there have been several papers that say lockdowns are ineffective.  The first I noted was in an Israeli publication called Mako and linked to by Townhall.
Professor Yitzhak Ben Israel of Tel Aviv University, who also serves on the research and development advisory board for Teva Pharmaceutical Industries, plotted the rates of new coronavirus infections of the U.S., U.K., Sweden, Italy, Israel, Switzerland, France, Germany, and Spain. The numbers told a shocking story: irrespective of whether the country quarantined like Israel, or went about business as usual like Sweden, coronavirus peaked and subsided in the exact same way. In the exact, same, way. His graphs show that all countries experienced seemingly identical coronavirus infection patterns, with the number of infected peaking in the sixth week and rapidly subsiding by the eighth week.

The Wuhan Virus follows its own pattern, he told Mako, an Israeli news agency. It is a fixed pattern that is not dependent on freedom or quarantine. “There is a decline in the number of infections even [in countries] without closures, and it is similar to the countries with closures,” he wrote in his paper.
Another one of those sayings is along the lines of "one paper doesn't mean much; several might".  An Oxford Professor says the UK's Covid epidemic peaked in March and the lockdowns now are doing more harm than good.

We can't talk about this story without Sweden coming up.  Sweden, of course, had a very laissez-faire response to the pandemic, and yet their results are "middle of the pack" among the European Union and neighboring countries.  As in other examples, most of Sweden's infections and deaths were in the highest population density portions of the country - around Stockholm.
Critics point out that Sweden’s per capita COVID-19 death rate is higher than several of its Scandanivan neighbors—Finland, Denmark, and Norway. Proponents point out that Sweden’s death rate is lower than many of its European neighbors—Belgium, France, the United Kingdom, Spain, and Italy—who initiated strict lockdowns. Proponents also point out that Sweden has “flattened the curve,” noting that the nation of 10 million has not seen its hospitals overrun or experienced medical equipment shortages.
...
“Whether or not they have openly embraced the Swedish approach, many other countries are now trying to emulate aspects of it. Both Denmark and Finland have reopened schools for young children,” wrote Professors Nils Karlson, Charlotta Stern, and Daniel B. Klein. “Germany is allowing small shops to reopen. Italy will soon reopen parks, and France has a plan to allow some nonessential businesses to reopen, including farmers’ markets and small museums, as well as schools and daycare centers.”
A standalone article on The Spectator about how Sweden lowered its 'R naught' number without lockdowns.

A professor of Political Science isn't the kind of guy you expect to have insights about viruses, but professor Wilfred Reilly does numbers and that's what it's about.  He writes "There is No Empirical Evidence for These Lockdowns" on Spiked.  This is quite possibly the money quote:
The question the model set out to ask was whether lockdown states experience fewer Covid-19 cases and deaths than social-distancing states, adjusted for all of the above variables. The answer? No. The impact of state-response strategy on both my cases and deaths measures was utterly insignificant. The ‘p-value’ for the variable representing strategy was 0.94 when it was regressed against the deaths metric, which means there is a 94 per cent chance that any relationship between the different measures and Covid-19 deaths was the result of pure random chance.  [Bold added - SiG]
If you love data visualizations, you might like this place.  Big shocker, I know: the best predictor in this multivariate analysis for fatalities is population density.

An interesting study by Stanford Medical School doctor Jay Bhattacharya was to test antibodies to the virus among Major League Baseball team staff members. This focused on staff; not the players, the other thousand people in the various offices.
The results of the MLB study showed that only 0.7% of the staff had the antibodies indicative of having had COVID-19.

Some staff is located in areas where antibody testing has been conducted for the general population such as New York, Los Angeles, and Santa Clara. Most of these locations showed the MLB staff had a much lower rate of prior infection than the general population. For example, the New York City metro area showed 25% of the population had antibodies. The MLB staff for the Yankees only showed antibodies in 1.64% of the employees. The Mets tested positive at a rate of 2.61%.
Dr. Bhattacharya said this seems to be basically their socioeconomic status and it's a trend he has seen in other studies he has done. Lower income residents had higher exposure rates to COVID-19 while the higher income workers had lower exposure.  Perhaps the lower income residents ride the subways while the higher income workers take private cars or other means?

The implication to Dr. Bhattacharya is that lockdowns might even be counterproductive.
“I think in the back of people’s heads there is this idea that somehow we can eradicate this disease if we just stay locked down. That is not possible. The serologic evidence, even the MLB study, suggest this. It suggests the epidemic is too widespread to eradicate. It spreads via asymptomatic contact. Like people who don’t have very many symptoms, even mild cold symptoms can spread the thing. They aren’t going to show up for testing. They aren’t going to show up at a hospital or a doctor.”
...
“There is no safe option. If you think that having a lockdown will provide you safety, you are mistaken. Because the problem is this lockdown has had enormous negative effects on the health of people in the United States and around the world.”
"Enormous negative effects on the health of people...?"  Since the lockdowns started, I've been saying we're only measuring one thing - the fatalities - and we're not measuring that accurately.  No one is tracking the actual costs and deaths from the lockdowns.  The National Institutes of Health ran this paper simulating the effects of the lockdown on diabetic patients, for example.  They conclude the longer the lockdowns, the worse the number of patients with diabetic complications.  

Early on in the spread of the disease, it was pretty easy to come to the conclusion that eventually everyone on earth will be exposed to this.  It's a new virus, and new viruses jump from animals to humans pretty regularly; it's simply how the world works.  I don't have strong numbers to base this on, but I believe the nationwide downward trend in new infections will continue downward, this numbers guy says the worst of the epidemic is over, but the virus will be back next fall.  It's my understanding that coronaviruses, as a group, are hard to create vaccines for.  The common cold is one of many such viruses that we're always exposed to, for example, and there's no good vaccine for the common cold, right? 

I'm not saying this is a cold; I'm saying it's in the same family of viruses.  OK, Google? 

So what do you do?  Covid-19, if it's unique at anything, seems to be very good at attacking the metabolically unhealthy.  The reason the death rates are the worst for those over 80 is that the majority of people in that group are metabolically unhealthy.  It's worse than that.  In the American population at large, less than 20% are ranked as metabolically healthy on five indicators that are assessed.  If you have high blood pressure, diabetes, a bad HDL:triglycerides ratio, existing heart disease or lung diseases, it might a good idea to isolate yourself. 

The surprising thing to me was how good blood levels of Vitamin D were as an indicator of surviving Covid-19.  Those patients with a measured blood level in the deficient range (under 20ng/mL) had a 10x worse chance of surviving the virus than those with normal levels of the vitamin (>30ng/mL), correcting for age, sex and other comorbidity factors (right plot here).  When you add that to the widely reported intolerance of the virus for heat and humidity, that might be a factor in the better numbers of Florida, Georgia and southern states as opposed to the Northeast.  Get outside in the sun, a few minutes a day to start if you've been locked indoors too long. 


A screen capture from an hour and a half podcast with those two guys whose images are stuck in the right graph; an American M.D. and an Irish biochemical engineer.  Interesting, but probably too geeky for most people. 



Wednesday, May 13, 2020

The Biggest Risk for the Next Starlink Launch is Weather

June first is the start of the Atlantic hurricane season, and it's rather common for some development to be getting started just about any day now.  This year is like that, with the NHC assigning a greater than 60% chance of development of a subtropical system to develop off the NE Florida coast in the next five days.


The next batch of 60 Starlink Satellites is scheduled for launch in the early morning hours of Sunday, four days away, at 3:53 am EDT (07:53 UTC), May 17th.

There are other interesting aspects to this launch, such as booster B1049 going for the elusive 5th landing that SpaceX has so far been unsuccessful at pulling off.  They say the boosters should be reusable 10 times, but have yet to recover any booster more than four times.  

It’s unusually important that this 7th Starlink launch goes perfectly, as any in-flight anomaly would almost certainly delay Crew Dragon’s crucial NASA mission. Additionally, if Starlink-7 slips more than a day or two, it could easily force SpaceX to push the mission into late May or early June, as Crew Dragon’s first crewed launch will also need a drone ship to recover its brand new Falcon 9 booster.

SpaceX moved their Pacific recovery drone Just Read The Instructions (JRTI) to the Atlantic in support of the increased launch cadence over here.  They've been doing some serious upgrades to JRTI, but don't think it's likely to be ready for these next two launches.  Which leaves them with one drone, Of Course I Still Love You (OCISLY).
Typically, OCISLY has taken around 7-10 days from port departure to arrival to recover Falcon 9 boosters after Starlink missions, most of which is spent being slowly towed by tugboats. In simple terms, assuming no technical or weather-related launch delays, that would give SpaceX just a handful of days to remove booster B1049 and turn OCISLY around to recover Crew Dragon Demo-2 Falcon 9 booster B1058. Unfortunately, to recover Starlink-7 Falcon 9 booster B1049, OCISLY is heading more or less straight for a tropical depression forming in the Atlantic Ocean. High seas in the recovery area are an almost guaranteed launch delay unless SpaceX is willing to expend B1049 (very unlikely).
Part of the whole mission to launch Starlink satellites is to test these "experienced" (not old!) boosters on their own nickel and not on flights that customers have paid for.  I tend to think they really wouldn't want to lose either B1049 or the brand new B1058.


Booster B1049, looking like a proper used spaceship, after her January 9th Starlink mission.  Richard Angle photograph.

Anything I'd put here for what I think is going to happen is just a WAG.  My guess is that they'll watch this weather system for a few days and decide as late as practical if they're going to go for it or delay the Starlink 7 mission until after the critically important Demo2 flight for NASA on the 27th.  OCISLY would have to be almost all the way to its assigned location out in the Atlantic by that time.  I have even less idea if they'd order OCISLY back in to Port Canaveral or not.  Although the article didn't mention it, at least one booster was lost after a successful landing because the seas were too rough and the booster slid around on the deck before it could be secured.  Nobody wants to see that happen. 



Tuesday, May 12, 2020

Have You Had Enough Stimulus? Part Deux

I've been beating the dead horse of creating money out of thin air for the life of this blog, so this is part two only in the sense of a post with a similar name in early April.

I heard today that House Democrats are working on another stimulus bill, this time in the vicinity of $3 Trillion.  It's all very preliminary at this point, but the Financial site The Motley Fool reports on what they're seeing in the early discussions.  Note that this is not an exhaustive list -- the actual bill is over 1,800 pages long and you can only imagine what sorts of handouts for favored groups are included in this.
  • Almost $1 trillion for state and local governments;
  • Another stimulus payment to individuals;
  • Hazard pay for essential workers;
  • $75 billion for coronavirus testing and contact tracing efforts
  • Instead of expiring at the end of July, the $600 weekly boost to unemployment benefits would last through January;
  • $175 billion for rent, mortgage, and utility assistance for affected households;
  • Funds for election safety and to help make voting by mail easier;
  • Money to help the struggling U.S. Postal Service.
Thanks to the first three (four? who knows?) packages, the US Debt Clock shows our total debt has ballooned to over $25.1 Trillion.  The Motley Fool isn't very confident that anything that passes the house will pass the senate and points out some obvious contentions, such as those last two bullet points.  That doesn't mean that something won't pass, though it's just a matter of how much pork gets pushed through.

How big is a trillion dollars?  I thought I'd pass along a couple of visualization exercises that are my favorites.  The first one is that the number of seconds in a year is within 1/2% of pi times 10 million (that was in a freshman physics class nearly 50 years ago and stuck in my mind).  So what?  That fun fact leads to simple visualization; if someone sat at a window and threw out a $1 bill every second of every day for a year, they'd throw out just over $31 million.  Make it an 8 hour day (1/3) of a year, and it's $3/second to throw out $31 million and so on.  To throw out $3 TRILLION at $31 million/year would take 96,774 years - and 10 weeks.  Clearly we'd need to step up our game.  If you can imagine something that threw out $95,066 per second, 24/7/365, or $285,200 every second for an 8 hour working day, that would get you there.

In the first year of this blog, I used some visualizations from Demonocracy.info and I was pleased to find they're still there.  They present a series of pictures on the national debt (they stopped updating the numbers back in '17 when the total debt was a mere $20 Trillion.  Ah, the innocent days of our youth.)  Here's $1 Trillion in pallets stacked with $100 bills. 


One Trillion Dollars.  
 Each of those cubes you see is a pallet of $100 million in $100 bills.  At the far end you can see an American football field with a Boeing 747-400 parked on it. You can see the White House with both wings to the right.

Just triple that area and you get the $3 trillion they're talking about for this spending bill.  Alone.

Look, I know that there's a lot of suffering out there, I just think this is exactly the wrong thing to do.  When someone has a compound fracture, you don't just give them a pain reliever; you fix the problem.  This is a band-aid.  We're doing Modern Monetary Theory and that's going to end in a worse disaster than we have now.  This could be the thing that destroys the economy and the entire western world.  



Monday, May 11, 2020

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.


Sunday, May 10, 2020

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. 



Saturday, May 9, 2020

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.



Friday, May 8, 2020

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.



Thursday, May 7, 2020

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.  


Wednesday, May 6, 2020

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.



Tuesday, May 5, 2020

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.