To see more of my posts on Launch Pad, click here.
Note: The schedule had Kevin’s lecture today swapped with his lecture yesterday. Today is really space environment. Yesterday was actually gravity, newton, kepler, orbits.
Mass in space:
There is no mas sin space, outside of planets and stars, etcetera. That’s why it’s called space.
Though strictly speaking, that’s not true; there are about 16 atoms per cubic inch, on average. This is much less than in the vacuums we create in laboratories.
The solar system is immersed within a local maximum (local fluff) which is, itself, immersed with in a larger, though still “local”, minimum. A local bubble. When we talk about local fluff, we’re talking about small changes in a very, very, very large vacuum. This mattes when we’re looking through light years of it. Even though there’s not much of it, it shows up.
Our sun puts out a constant stream of particles. Among them are alpha particles, helium nuclei. There’s a constant stream of material streaming off stars.
But space is pretty empty.
Sound in space:
None. The medium is not dense enough.
Strictly speaking, you could have sound in space if you had a really, really, really big explosion. In your stories, though? Not happening.
Magnetic fields:
Magnetic fields are created by moving, charged particles. Whenever you have a current, you have a magnetic fields. Magnetic fields are in the core of planets and in suns because you have a lot of moving, hot material.
Moving, charged particles are deflected by magnetic fields. Once you have an existing magnetic field, a charged particle that enters into that field is deflected.
Earth’s magnetic field, approximated, looks like a cored apple. A magnet within the field will align itself with force lines. That’s how compasses work.
Venus has remanent magnetization. Imagine you have melted material, magma. In that magma, different rocks and minerals will crystallize at different temperatures.
These magnetic fields are life-sustaining. There’s plenty of healthy= risks i space. Magnetic fied reject charged materials, so when the sun spits charged materials at us, they can’t get that far.
Temperature of space:
27 kelvins (not degrees kelvin, but kelvins. that’s the proper use. so you could write about it as if scientists said kelvins, and non-scientists said degrees kelvin.)
That’s somewhat misleading–if you’re illuminated by the sun, for instance, then that’s going to warm you up.
It’s also misleading due to mass density. Heat is energy transferred between bodies, orbetween a body and its surroundings, as a result of temperature differences only. 1) Conduction, like sitting in a bath, or touching a stove. 2) Convection occurs when and only when you have a fluid heated from below; fluid, to a scientist, is a state of matter that will flow, a liquid, plasma, gas, or sometimes a rock. 3) Radiation, when it comes to heat in a star environment, radiation is pretty much it. That’s electromagnetic radiation, not particle radiation.
What if you, as a human, was exposed to space? Would you freeze?Yes, eventually you would freeze. It would take several thousand years … because there’s nothing to carry away the heat, since there’s so little density in the vacuum. There is no medium to carry away the temperature. There’s only radiation to create an equilibrium in temperature, and that’s a slow process.
So what would happen to you? Would you pop? Not if you didn’t hold your breath. The bends are pretty nasty, though. If you don’t hold your breath, the air will go out your mouth, and out your nose, taking the path of least resistance, instead of going through your chest. The air in your blood though will bleed out, bursting blood vessels in eye, ear, nose, skin. Also, when you inhale, your body absorbs oxygen, but also nitrogen. When you undergo sudden depressurization, nitrogen bubbles into your bloodstream, causing “the bends”–or decompression sickness–which has a lot of symptoms, and particularly makes the joints very painful.
So in space, you would survive… you’d have about 20 seconds of useful consciousness before your brain faded. You could probably survive about 2 minutes of exposure, if you were rescued by someone else.
Jane Espenson, intro to the science of battlestar gallactica–“When I needed to describe the effects of death in a vacuum, I needed to resist rumor (“Your lungs pop out of your nose!”) and find out what really happens. (Your lungs don’t pop out your nose or anywhere else interesting.)'”
Single event upsets–when a charged particle like solar wind, a cosmic ray, which can hit a bit in your compute rand change the value from zero to one, which could cause you to “jump” in a science fiction show to a place that was completely unintended. People wondered if this could really happen when Kevin recommended it as a plot point to BSG, but a few days later, a real event happened that proved it could.
Monte Cook asks Say you’ve got an oxygen tank and a mask and you’re blown into space. How does that change things? Kevin says, pain–you’d have a spreading, creeping pain as your blood vessels break, and the alveoli in your lungs break, and the fluid in your ear canals start to boil and eeeeep.
Sex in space–conception, birth, etc. Kevin says they’ve done experiments with animals breeding in space. Zero g turns out to be bad for fetal development. He doesn’t know details, but rodents that conceive in space give birth to deformed progeny.
NASA’s not about science, says Kevin. It’s about engineering. Putting stuff into space. Building, designing, operating stuff. There are science people in academia that work with NASA, but he’s a rare scientist who does.
Bud Sparhawk, I’ve written a bunch of Sam Boone stories that center on intestinal gas. Humans have about 4.5 meters of intestinal gas. You’re a balloon. What happens when you expose that to space? Kevin says, via colorful anecdote, that the air gets expelled.
Van Allen belts between us and the moon. You pass through them so quickly that it just doesn’t matter, even though it’s high radiation. People argue about how to shield spacecraft from radiation, and there are discussions about shielding craft from radiation. Kevin says that he thinks the same factors that make space vessels prone to radiation could affect small planets; if you colonize a small planet, it might not be able to generate enough of a protective radiation shielding.
There are issues in getting into and getting out of space that have to do with accelerations, and the human tolerance for acceleration, says Mike. Kevin says you can handle about 9Gs. Mike says one of the books (listed below) has tables about what you can survive, when you pass out, and so on.
Kevin says 9G is G-lock, and you can see it coming, and you know, no ifs ands or buts, you will pass out. The only thing you can do is put your plane in such a position that when you wake up, you’ll be okay. You wear high-G pants, when you plane makes a high G maneuver, the pants squeeze the air, trying to force the air back into your head. Your tolerance will vary based on the orientation of the plane. If you’re in positive G, you can do 9, if you’re in negative, you can’t. How long do you pass out? Kevin says 20 seconds or so, which is a long time at those speeds. If you pass out, you can think about you’re about to pass out, then you go grey (your visuals doing poorly), then you go black. If you are traveling negative G when you pass out, you go red instead.
Air Combat USA in Los Angelos will train you how to dogfight, a bit, for about $1000. Kevin says he did it and flew to 5G.
Mike recommends books that he uses as references for topics that come up over and over in science fiction, like what happens when you’re exposed to vacuum:
Sex in Space by Laura S. Woodmansee
Teaching Science Fact with Science Fiction written and illustrated by Gary Raham
Spacefaring: The Human Dimension by Albert A. Harrison
The Giant Leap: Mankind Heads For the Stars by Adrian Berry
Do Your Ears Pop in Space? by R. Mike Mullane
Because that moving charged particle, on the basis that it is both a) moving and b) charged, has it’s own magnetic field. Its magnetic field and the magnetic field it’s moving towards (or through) interact, either attracting or repelling each other depending on their alignment with each other.
Not a good explanation. As I noted above, magnetic fields do not so much reject charged materials as they change their alignment. So when the charged particles streaming from the Sun (our primary star is capitalized, but when using the word to refer to another planet’s primary star do not) hit the Earth’s magnetosphere some are deflected around the Earth. But others are attracted, following the Earth’s magnetic field force lines down to either the North or South magnetic poles. At least they try to – but when they hit the atmosphere they interact with the oxygen and nitrogen molecules in the atmosphere. The particles lose energy in that interaction. Some of that is expressed in electrical discharges that can interfere greatly with radio, TV, etc. communications. Some other of that ionizes the atmospheric gases and drives them to higher molecular quantum states. As they relax down into lower states they give off photons to carry off the energy difference, giving us the sometimes spectacular displays of aurora borealis and aurora australis. Aurora of this nature have been observed from satellites on both Earth and IIRC other planets.
Note that there’s another useful related effect. When a conductor (i.e., something made out of metal or carbon fiber) moves through a magnetic field an electrical current is induced in it. Fly a metal ship rapidly through a strong magnetic field and interesting things can happen.
Amazed to see this here. Better: “…, but they are rare scientists who do”, or “he or she is the rare scientist who does.” I worked with far too many women in labs to let this pass.
When I learned the difference between the Celsius/Centrigrade, Fahrenheit, Kelvin and Rankine temperature scales in the Chemical Engineering courses I took at MIT our instructors used the term “degrees Kelvin”. I never heard anyone use the term “Kelvins”. BTW, so you know: 1 degree Kelvin = 1 degree Celsius, except that the zero point in Celsius is the freezing point of pure water under standard atmospheric pressure, whereas the zero point in Kelvin is absolute zero, or -273.15 deg. Celsius. So 27 deg. Kelvin = ~-246 deg. C, which will keep your beer cold for a while.
If you live near the San Diego area, go on Neptunus Lex’s blog and ask him who he flies for. He’ll give you and a friend lesson or two in dogfighting, too, and you can fight each other. Lex used to make his living flying fighter jets off of (and back onto!) aircraft carriers.
Which is why the Space Shuttle a) has 5 computers and b) does not use the most current Intel CPUs. The CPUs (8086’s, I think, quite old) were especially hardened to resist radiation and NASA didn’t fund hardening Pentiums, and it had 5 so that if one went haywire because of this (or other) phenomena, the other 4 could outvote it and tell you to ignore it.
The sweat on your body would sublimate away and carry off heat just as evaporation cools you off on land. I don’t know how much, though. Maybe enough to freeze the outer couple of millimeters, until it cracked from the internal pressure. That’s just a guess, though.
Engineering professors may use “degrees Kelvin,” but that is not the correct use. Kelvins work like any other SI unit that is measuring numbers of things (things that can’t be negative, unlike degrees Celsius or Fahrenheit.)
Correction: 4.5 liters of intestinal gas, not meters. h/t Bud Sparhawk
As well as losing heat from sublimation of sweat, you’ll also lose energy through black body radiation at a rate of around 600 to 1000 W. This will eventually cause you to die of hypothermia (if you were naked in space, but had an air supply, and if you were in shadow relative to the Sun, as the Sun is radiating with more power at Earth’s orbit than a human body radiates. In space, and not in shadow, you’d get hotter on one side and colder on the other). For comparison, shivering generates heat at a rate of about 200 W. It might take thousands of years for you to cool to the background temperature, since you would radiate less and less power as you got colder and colder, and it would take a long time even to get down to freezing, but hypothermia would kill you long before then.
Human blackbody radiation is in the infrared range and is what allows you to see a person using IR goggles. Probably obvious, but in one of your earlier summaries you wrote “In principle, every once in a while, humans zing off a few photons–not very many because we’re not *that* hot, but some because we are–but we can’t see them because they’re insignificant.” We can’t see them because they overwhelmingly aren’t in the visible range, but there are enough in the IR range that they form a continuous image rather than just a faint trace of sparkles. Maybe you meant in principle every once in a while we zing of a photon in the visible range?
I really appreciated the explanation of why there are no green stars. I assume the same explanation applies to why a clear sky goes from reddish to bluish at dawn and twilight without ever passing through green, which is a question I have puzzled over for at least 2 and a half decades!