Random mutterings from science!
(Picture from here.)
Let’s start with the SLS—NASA’s Space Launch System.
The SLS was initially scheduled to launch at the end of August. This was cancelled because of a coolant problem with one of the engines. Rocket engines burn hot and hydrogen/oxygen engines burn really hot. To correct for this, the hyper-cooled liquid hydrogen is circulated through the engine bell prior to combustion. This has two positive effects: it keeps the bell cool and it pre-heats the fuel. Thus, not being able to cool the engine is a big deal. Scrub launch number one.
Launch number two was scheduled for early September. It also got cancelled because of a hydrogen leak. Hydrogen is such a small molecule that when it’s cold and under pressure it can escape easily. The SLS sits on the pad getting continuously topped up through fast disconnect valves. Just before launch, the valves disconnect and the SLS takes off. A little hydrogen leakage is accounted for but this was too much. Next launch is latter September.
The issues with hydrogen are well known—this was a continuing problem with the shuttle and the SLS is based on shuttle technology. Why base the SLS on technology from the seventies? Blame congress. We have to keep Morton-Thiokol in business.
Personally, I want the SLS to succeed. I like the idea of NASA having its own rocket and I hate seeing NASA used as a punching bag all the time. The glorification of SpaceX gives me heartburn. Often, it’s an excuse to say government can’t do anything.
I don’t agree with that sentiment. For example, SpaceX has trumpeted it set the record of 40 missions this year. (See here.) No government can do that, right? Well, China launched orbital launch 36 and 37 recently. SpaceX may be the world leader in orbital launches but China is not far behind.
Bridgestone is moving away from using oil in the manufacture of its tires to using a plant called guayule. It takes on the order of seven gallons of oil for each tire and more than 2 billion tires are made every year. It is good news that Bridgestone (and other tire manufacturers) are moving away from oil. But 2 billion tires are going to require a lot of guayule.
This is an inherent problem with moving away from fossil material. When we pull oil out of the ground we’re taking advantage of millions of years of captured sunlight. It takes about 200 tons of plant material to make a gallon of crude oil. (I pulled this from here and combined it with here.) Using bamboo as an example, that’s about 28 acres over a season of about five months or 150 days. So, one tire, using seven gallons of oil, is on the order of 200 acres. You can imagine how much 2 billion tires is going to cost. (That does presume a gallon for gallon equivalent which may not occur.)
Those numbers weren’t in the article but it’s a problem. How to capture enough sunlight to drive civilization is a problem. One solution is for tires not to require seven gallons of anything. And maybe not require 2 billion per year.
On a similarly negative note, Greenland is going to raise sea levels.
A recent study has managed to model the quantity that is already baked in to Greenland glacier melting. They can’t say when it’s going to happen but by neglecting that aspect of things they can tell how much.
They did this by calculating how much of the Greenland ice is vulnerable to current conditions, current conditions not going away any time soon. This allowed them to calculate how much water would come from those vulnerable glaciers. The answer was enough to raise the world sea level close to eleven inches. When? That is not part of the study but warming is still increasing and we’re not close to stopping the problem.
On that happy note, another study has suggested it was actually hotter 55 million years ago than previously thought. This, probably not coincidentally, took place in or around the Paleo-Eocene Thermal Maximum, though the study doesn’t reference the PETM. The timing is about right in that the study takes place between 35 and 60 million years ago and the PETM took place about 55.5 million years ago.
The point of the study was that since the time was hotter with understood CO2 amounts, the environment might be more sensitive to CO2 than previously thought.
The technique was pretty interesting. The measurement was of carbon and oxygen isotopes in the shells of foraminifera. Earlier studies measured the oxygen/carbon isotope ratio directly. However, depending on temperature, isotopes “clump” together. Isotope clumping can be calibrated to temperature without the need of determining salinity or other factors. That’s the good news. Bad news is, of course, it was significantly hotter than previously estimated.
Let’s go to some not-quite-so-negative news prior to the finale.
This involves my favorite small animal, tardigrades. Tardigrades are tiny animals called “water bears” that live in water droplets in moss. Or salt or fresh water sediments. Or in deep sea trenches. They have my vote for the most likely alien visitor. They go from a normal moist environment to a tun state when that water dries up. When in tun, tardigrades can withstand vacuum, high impacts, etc.
Tardigrades dehydrate pretty much completely when going into tun and they stay that way until they either fall apart or get more water. It’s been a mystery how they do that.
In 2017, a paper demonstrated they used a disorder protein (“tardigrade-specific intrinsically disordered protein” or TDP) that suspends the cell so it doesn’t collapse when the water disappears. The new paper presents a different mechanism. Instead of suspending in a glassy TDP substance, the new paper suggests that “cytoplasmic-abundant heat soluble proteins” (CAHS) are responsible. These form gel-like filaments rather than glassy material. The filaments appear during dehydration and gradually disappear during rehydration.
What’s even more interesting is they spliced the CAHS genes into insect and human cells. The proteins behaved the same way in insect cells and had limited functionality in human cells.
Drake was 92 and died peacefully in California. He had a long and distinguished career independent of his famous equation as a radio astronomer. Asteroid 4772 Frankdrake is named after him.
The Drake Equation was an attempt to formalize the probability that there was intelligent life in the Milky Galaxy. It did not solve the problem. It only presented it as a mathematical proposition shown above.
- N : Number of detectible Milky Way civilizations
- R* : Number of suitable stars created every year.
- fp : Fraction of stars with planets
- ne : Number of habitable planets
- fl : fraction of planets where life actually appears
- fi : fraction of life bearing planets where intelligence appears
- fc : Fraction of those planets where a technology arises that can be detected
- L : Length of time a given technological civilization produces detectable signs.
We are only now getting a sense for some of these variables. R*, for example, depends on what kind of star we’re considering. If we’re only talking about G-type stars, like our sun, than that is one rate of formation. However, recently red dwarfs are also being considered since they are so long-lived. They have issues, too, like lethal solar flares. fp has some data, too, from the Kepler and TESS missions. We have an inkling of ne in that we’re getting an idea of how many rocky planets might be in the habitable zone but no real idea if they’re habitable. The rest are unknown. Thus, the Drake Equation is really a valuable mechanism for discussion and speculation.
Thanks, Frank. We’ll miss you.