Selenian Boondocks

CDC Statement on first possible community transmission case of COVID-19 in the US

So, given that the CDC recently confirmed the first possible instance of community transmission of COVID-19 (Novel Coronavirus) in the US, I thought I’d guesstimate roughly when the peak of the epidemic would occur in the US with some (extremely) rough modeling.

I’ll be modeling it using the usual logistical model (which I think turns out to be the wrong model for a virus… but let’s just run with it for now) you all learned in your first Differential Equations course. I’ve recently been brushing up on my differential equations (have been getting rusty) in Khan Academy: https://www.khanacademy.org/math/differential-equations/first-order-differential-equations/logistic-differential-equation/v/modeling-population-with-differential-equations

The rate of change of the population N (in this case, Coronavirus cases) with respect to time can be given as:

dN/dt = r*N*(1-N/k)

Where r is the exponential constant (related to doubling-time) and k is the “carrying capacity”, i.e. max number of cases (not actually a good definition for a virus… but again, let’s run with it).

This is solved as: 

N(t) = N0*k/((k-N0)*e^(-r*t) + N0)

Where N0 is the population at time = 0.

At the beginning, the number of cases rises exponentially. Early research says the doubling-time of COVID-19 was 7.4 days in the early days of the outbreak in China, according to: Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus–Infected Pneumonia

This is related to the exponential constant by:
r = ln(2)/(7.4 days) = 0.09366853791 (1/days)

According to Wikipedia, 28% of the US population became infected with the Spanish Flu (carrying capacity?): https://en.wikipedia.org/wiki/Spanish_flu

And US population is currently about 327 million people, so we’ll use 91.56 million as our “carrying capacity”:

k= 9.156*10^7 or 9.156e7 (in more compact notation)

And since community transmission just started, we can set N0 = 1. Therefore our equation becomes:
N(t) = 9.156e7/((9.156e7-1)*e^(-0.09366853791 (1/days)*t) + 1)

If we plot t in days: 

modeled infected population vs time

https://www.wolframalpha.com/input/?i=9.156e7%2F%28%289.156e7-1%29*e%5E%28-0.09366853791*t%29+%2B+1%29+for+1%3Ct%3C365

So sometime before 200 days from now, COVID-19 should have peaked in the US. Taking the derivative with respect to time, we see there will be a period of about two months when the number of new infections per day will be super high:

US infected per day vs time (simple COVID-19 model) link

This compares fairly well with the peak of deaths for Spanish Flu in the US:

(Thanks again Wikipedia: https://en.wikipedia.org/wiki/Spanish_flu)

We can try overlaying these, and we see that the width of the peak of infections is fairly similar to the width of the peak of deaths from Spanish Flu in the US.

About two months of chaos, potentially. And we have about 5-6 months until this peak.

My model is pretty terrible. A virus doesn’t really have a carrying capacity in the same way… But it does seem to have pretty similar characteristics. I know almost nothing about virus modeling, this is COMPLETELY an amateur, toy model. A guess. There are professionals (like the CDC and the WHO) who do this for a living and you should listen to them, not me. Also, obligatory relevant XKCD webcomic: https://xkcd.com/793/

With the death of Mars One, there are no high-profile companies looking to settle Mars besides SpaceX.

Mars settlement future is currently single-string. Reliant on a single company. What can we do to change that?

Am I missing someone?

On a second note, I’m really missing XCOR. They had something special. SpaceX is doing very well. Has the right architecture for launch (reusability) and wants humans space settlement. And they have a drive to get it done quickly and execute. Blue Origin has only the first two (right architecture and wanting settlement), although hopefully the others will follow… someday?
XCOR had that (although their execution was well beyond concept phase, it did end up lacking a bit). They unfortunately did not have the financial backing of the other two. But they had something more, that’s kind of special: a sort of egalitarian sensibility. They were often fairly right-libertarian in spoken philosophy (as was common among early New Space companies), but they weren’t founded by charismatic billionaires or near-billionaires and so were more worker-focused. They offered free space rides (as part of the shakedown process for Lynx, as I understand it) to all their employees who wished it. That is something special.

So even beyond Mars, we basically have just two companies with the right mix of backing, vision, execution, and technology, and only one is really executing right now (Virgin Galactic seems too small right now… and with the split, seems less likely to be pursuing orbital anytime soon). It’d really be nice if we had a third or a fourth, particularly if they had an XCOR-like egalitarian esprit de corps. Perhaps Musk could eventually be persuaded to transition SpaceX in that direction? Or Bezos/Blue? (I wouldn’t hold my breath for either, but it is a possibility… You can’t have Musk’s democracy on Mars without, you know, democracy… but power is seductive.)

Additionally, I have some ideas for space commerce that require the ability to launch one or two people to Earth orbit (with recovery) for less than a million dollars (ideally <$100k). But on a dedicated launch. XCOR had that, see here: https://spacenews.com/34930xcor-aerospace-makes-plans-for-reusable-orbital-vehicle/

https://spacenews.com/34930xcor-aerospace-makes-plans-for-reusable-orbital-vehicle/

 

 

…but neither SpaceX nor Blue appear to be offering anything close to that now or in the future.

I am considering sponsoring a capstone project at Florida Polytechnic this year. I believe I have a compensating nozzle that could be checked out within the two semesters the project would last. I had an intern from the school this last summer to work on remote control and robotics for small construction equipment. If I can get them to move on hardware, we should have cold flow tested before Christmas.

If Verification of compensation with cold flow is done, does anyone have a connection with hot fire testing capability that could be done at little or no cost? If so, what sizes and what propellants would be allowable?

I have lost touch with the people that I would have asked a decade ago. And several of the companies they were associated with are gone.

In 2016 when Elon Musk unveiled ITS, everyone thought it was ridiculous and huge. It dwarfed the Saturn V. People were scratching their heads as to how it could possibly launch from LC-39A as pictured, since the 42 Raptors were to produce 128 MegaNewtons of thrust, almost 4 times the Saturn V. SpaceX had only ever launched the Falcon 9 at that point and just recently had started landing them. But now they’re proposing something 4 times the thrust of Saturn V with 42 engines?? Outrageous! Surely that will put a bunch of buildings in danger, exceed the limits of the pad, and cause major problems on the Space Coast. And who even NEEDS a rocket that big?? And the upper stage is a reusable SSTO! Impossible!

In the time since then, ITS (the Interplanetary Transport System which was, before 2016, known as the MCT, or Mars Colonial Transporter–a name not likely to go over well with those with a recent history of European overlords) became BFR (Big… um, Falcon Rocket) and then finally Starship. It went from 42 Raptor engines of 300 tons of thrust, down to 31 of 170 tons of thrust and now, in a tweet, Musk said first flights of the booster would only have “around 20” Raptors: https://twitter.com/elonmusk/status/1131625229367693312

Raptor has achieved its 172 ton thrust, and so absent subcooling of the propellant, that’s likely where it will be for the first operational missions (or perhaps slightly less for margin).

172 tons of thrust times 20 Raptors (could be 19, which packs better) is just 34MN, or just shy of Saturn V. And in the meantime, SpaceX has launched 2 Falcon Heavies, the first one a lower thrust pre-block-5 version and the last one a full thrust block 5 variant. Its 27 engines worked fantastically and produce about 23 MN of thrust. SpaceX has also been building and test-firing flight versions of the Raptor engine, even testing integration into a battleship demo vehicle, the Starhopper. The initial BFR (I’m still calling it that) will have less than 50% more thrust than the rockets SpaceX already is launching. And its possible SpaceX may use, say, 18 engines and throttle them down to 80% for reliability reasons. That’s basically the same as Falcon Heavy, has fewer engines, and addresses all those concerns about flame trench size, infrastructure risk, etc. (Although I suspect that SpaceX will operate with higher thrust.)

BFR is now no longer absurdly over-sized at all. That talking point is over. It’s easily within their demonstrated capability. Fewer staging events also helps. And landing the Super Heavy booster may be easier than landing 3 separate cores simultaneously (no one knows right now). They switched from carbon fiber to stainless steel for fabrication, but that’s probably a step in the right direction if you want the vehicle to fly realsoonnow. Hypothetically (with almost balloon tanks), stainless has the same mass fraction as a carbon fiber (which needs design knock-downs for cryogenics and oxygen, particularly with out-of-autoclave processes) and similar to SpaceX’s current aluminum-lithium alloy. In practice, it seems SpaceX is still literally hammering out the manufacturing process. They have a method that seems to work with Starhopper, but the mass fraction is terrible (built literally by a water tower company). It seems almost like Sea Dragon.

But they don’t HAVE to have extremely good mass ratio. The upper stage doesn’t HAVE to have SSTO-like capability, not at first. It just needs enough to get to orbit with significant payload, say 50 tons. Perhaps it just needs 6.5km/s. That’s also about the delta-v needed to go from the Gateway to LLO then to the lunar surface and back (well, that’s about 6.2km/s total… 5.2km/s if you’re aggressive with your burns).

The difference between 6.5 and 9.5km/s when your exhaust velocity is about 3.7km/s is: e^((9.5-6.5)/3.7) = 2.24. So while SpaceX might be able to theoretically do SSTO with extremely good mass fraction, they can knock that down by a factor of about 2.25 (including long-duration equipment) and still accomplish the mission. That means they may be able to use a fairly crude manufacturing and heatshield system and still accomplish the initial goals of Starship. In fact, Elon has also been discussing an expendable upper stage for certain missions. That gives more options for SpaceX to insert Starship into some operational role much earlier than you might think.

It’s no longer pie in the sky (although the capability is also much lower, but perhaps sufficient). Of course, most of the professional spaceflight community hasn’t grokked that yet. We’ll see how long that takes. With Starlink, it took the splendid orbital launch of 60 satellites for anyone to even raise the question about night time visibility of 12,000 LEO satellites, even though the likely operational visibility was perfectly predictable when it was first announced.

So, the other day I listened to a presentation from the FISO (Future In-Space Operations) working group. They have regular online telecons which anyone can listen to and follow along after the fact on their web archive:
http://fiso.spiritastro.net/archivelist.htm

It was titled “Preparing to Survive: The Case for Disabled Astronauts and Colonists”
http://fiso.spiritastro.net/telecon/Wells-Jensen_5-22-19/

I highly recommend this one as it’s off the beaten path, out of the box, and has some very interesting things I hadn’t considered before.

One of the most fascinating things I learned is:
Some deaf people are complete immune from dizziness from (for example) short-arm centrifuges. That certainly makes artificial gravity easier. Trivial, even.

Another was a more philosophical point. We’re going to bring our humanity with us. We can’t rely on the fighter jock physique. Even if we start that way, injuries can easily happen along the way, so we better be thinking about designing our spaceships and habitats with accessibility in mind. And maybe.. Just maybe… if everyone is blinded from long-duration exposure to microgravity or from smoke or some chemical accident, it might help to have someone on board not reliant on sight. Or at least you should have a spaceship that is still usable without relying on perfect sight. Or if everyone is disoriented on landing on Mars from months in microgravity, having someone immune to dizziness to guide you might also prove useful.

Very thought-provoking talk. I recommend it.

Neal Stephenson in his novel Seveneves coined the term “Amistics”, deriving from how some Amish people have strong preferences for certain technological paths to achieve the same goal. For instance, these Amish folk swear off modern technology, which for them means electricity. Therefore, they cannot use electric power tools for their furniture-making. Instead, they use just-as-modern air-powered tools. Similar productivity, same result, but they’re able to honor their cultural proclivities. In Seveneves (not to spoil it for Jon), similar proclivities develop in the groups mentioned in the book.

Spaceflight is rife with examples of this. One is the pro-vs-anti hydrogen schools of thought. Dumb, mass-produced expendable vs high tech reusable. But probably the most important for the future of humanity is the amistics of robots vs humans.

It gets started at the beginning of the space race in another example of technology path-dependence. Due to the US’s earlier start, America’s nuclear weapon technology had significantly more advanced miniaturization technology than the Soviets. For reasons I’m not entirely sure of, the US also maintained a very strong advantage in electronics and computerization. Additionally, the US had an advantage in long-range bomber technology. This led to the fact that the Russians focused on ICBMs while the US focused on long range bombers. And secondly, that the first Russian launch vehicles were ENORMOUS in comparison to the US’s. Russia developed the R7 and the Proton in part to be able to lob their nuclear weapons, which (from my limited knowledge) lacked both the miniaturization and precision of their American counterparts. The R7 was so big, that they could use it to launch Sputnik to orbit. And later on, the first crewed launch (Vostok), and eventually even up to 3 people on a single rocket that is used to this day. The US, on the other hand, was caught by surprise by the advanced Soviet ICBMs. Large ICBMs like Proton were not required due to better targeting and miniaturization, thus the US had to develop heavy launch vehicles intently for spaceflight purposes.

And thus the Soviets racked up success after success in the early history of human spaceflight due to the path dependency of tech development. It was only after a concerted, civilian-focused effort of development that the US exceeded the Russians, by an enormous margin.

But the Soviets maintained some of these advantages. They pressed their early leads in human spaceflight and while the US rushed to the Moon, the Soviets developed crewed space stations designed for surveillance. The Almaz program launched Salyut 2, 3, and 5. Soviet military personnel conducted surveillance from orbit in real time. The Americans, for their part, had a similar program, the Manned Orbital Laboratory, or MOL, based on Gemini technology. An uncrewed demo of the capsule was launched, but the program was cancelled soon (in 1969) as it became clear that automatic satellite surveillance was sufficiently advanced that it wasn’t required nor worth the cost. The US’s lead in automation again struck a blow to human spaceflight.

About a decade after (1978), the Soviets came to a similar conclusion and ended their manned orbital surveillance program. But not before advancing their space station technology sufficiently to place them at a dramatic advantage over the US in long-duration human spaceflight (as measured by orbital refueling, human spaceflight duration records, etc), an advantage that STILL has not quite yet been eclipsed (although it’s close). And because of the early focus on large launch vehicles and human spaceflight over miniaturization and automation, the Russian human spaceflight program survived the fall of the Soviet Union and to this day US NASA astronauts rely on Russian vehicles to get space.

Now, humans make terrible surveillance satellites, but these historical examples should make us think twice about whether the best way to push for a future where millions are living and working in space is to invest in miniaturization and automation. Because in my opinion, the most likely result is that any useful things a human can do in space will become obsoleted by robotics much faster than otherwise, thus reducing the need for humans in space at all. That’s not a winning strategy, IMHO. So I hope to blog later about how we can use humans in space MORE, in direct contradiction to the current trendy meme of increasing robotic automation in space.
We need to:
1) Find things for HUMANS to do in space.
2) Make it cheaper for humans to go to space.
3) Make it cheaper for humans to live and work in space.

We need a pro-human amistics, not the current pro-automation amistics (even when it doesn’t make sense, like when Elon tried to fully automate Model 3 production and had to switch over to human assembly). We need to engineer systems very close to the humans, including perhaps modifying the human body itself (or at least developing advanced biomedical countermeasures) to make humans more competitive with robotics in space.

By Chris Stelter

Blue Moon, the recent announcement of an uncrewed lander by Blue Origin, had flare and pomp. A starfield surrounded the select audience as they watched Jeff Bezos, the richest man (okay, if you count his family) in the world, deliver an anticipated announcement. They waited patiently as Bezos gave his usual spiel about Earth being the best planet, about the criticality of reusability, about a trillion people living in O’Neil colonies, about moving heavy industry to space. Then Bezos unveiled…

An expendable descent stage with less payload capacity (3.5 tons) than the Apollo LM truck variant (5 tons). Because it uses liquid hydrogen, it’s very tall and therefore needs a sophisticated mechanism for unloading payloads.

It was so anti-climactic. Everyone knew Blue Origin was working on this lander, I was sure it was going to be something more important or at least *innovative*. I’m not sure if the rocket engine is pumpfed or not, but the lander is designed as if it’s pressure-fed, with Apollo-like large round tanks with external structure.

Its example mission is… landing several smaller payloads simultaneously. Basically, competing with all the smaller lunar lander companies out there. Super disappointing there as well.

It’s like a tiny, uncrewed version of Altair with all the drawbacks but without the advantages of a 16 ton payload capacity. And sure, they showed an ascent stage on top of it, but that appears to be provided by NASA.

In fact, let me list off some concepts I think are better:

1) Starship. Obviously. Fully reusable, much larger payload capacity, crew capable, and being crudely prototyped right now in Texas, not just made into a fancy mockup.

2) The reusable Lockheed Martin lander. Dinospace is not supposed to be this much better, but this is a lot more interesting than Blue Moon.

3) ULA/Masten Centaur/Xeus. More payload capacity, still hydrolox, much closer to the ground. Looks to be a more efficient design. Some of the hardware already exists in some form.

4) Altair. At least they were trying for more capability than Apollo.

5) Apollo LM/LMtruck. 5 ton payload capacity, much closer to the ground. Crewed variant was the only one that flew, so it started out crewed.

6) The Soviet LK lander. Crasher stage FTW. Less payload, but the Soviets did a fine job systems engineering a clever way of dealing with the constraints they were given by the much-less-to-TLI N-1 rocket.

7) Various crasher/uncrasher lander concepts, as discussed here.

8) Delta Clipper on the Moon. If Delta Clipper had been successful, there was thought given to variants of it for Moon or Mars. If you have a SSTO VTVL RLV, why not refuel and go to the Moon? Basically, like Starship. Bezos hired a bunch of old DC-X folk. Why such a mundane lunar architecture?

Blue Origin gets like $1 billion per year from Bezos. Couldn’t they come up with something better than Blue Moon? Or at least something that didn’t look designed to squash the other small lunar lander outfits? A reusable upper stage? A reusable lander? Anything?