Weirdest space fact that you know

[kerbiloid]

Venusian descent helmet
 

Spoiler

Decreases the terminal velocity down to 5 m/s by proper shape.

Pointed down, protects you on reentry.

 

Edited November 23, 2020 by kerbiloid

[starcaptain]

The main limiting factor of why we can't reproduce in space is that a lack of gravity [very likely] hampers the development of a proper cardiovascular structure for a human being. Without the pressure and resistance caused by gravity stresses, an infant's heart would be only strong enough to survive nominal and low-stress microgravity conditions. The physical stresses of being born would [very likely] be fatal.

[K^2]

6 hours ago, starcaptain said:

why we can't reproduce in space is that a lack of gravity

Well, that's what artificial gravity's for, among other things. Just one more reason not to waste time trying to figure out habitation in microgravity.

[magnemoe]

5 hours ago, K^2 said:

Well, that's what artificial gravity's for, among other things. Just one more reason not to waste time trying to figure out habitation in microgravity.

This, its not that its even hard if you build an space station so large you would raise kids on. 
Mars might be more of an problem here if 1/3 gravity is not enough. 
Yes its possible with an spinning bowl construction but this is far harder to build and maintain than spinning up an large space station. 
 

[Spacescifi]

6 hours ago, magnemoe said:

This, its not that its even hard if you build an space station so large you would raise kids on. 
Mars might be more of an problem here if 1/3 gravity is not enough. 
Yes its possible with an spinning bowl construction but this is far harder to build and maintain than spinning up an large space station. 
 

 

The interesting data is the required radius or length of a spaceship or tether pods to do 1g rotation at 1  RPM  (one revolution per min).

100 meter disc spaceship radius OR 100 meter long tether pods or 100 meter long spaceship with crew only living on the ends.

Take your pick out of three.

Elon's spaceship is slightly over 100 meters long, so he has the option of rotating tge entire ship and putting tge crew at the ends or extending 100 meter tether pods before spin. The first option is arguably less complex.

 

This ONLY works if his spaceship is over 100 meters long AFTER staging detachment.

 

If not he can't.

Edited November 26, 2020 by Spacescifi

[magnemoe]

25 minutes ago, Spacescifi said:

 

The interesting data is the required radius or length of a spaceship or tether pods to do 1g rotation at 1  RPM  (one revolution per min).

100 meter disc spaceship radius OR 100 meter long tether pods or 100 meter long spaceship with crew only living on the ends.

Take your pick out of three.

Elon's spaceship is slightly over 100 meters long, so he has the option of rotating tge entire ship and putting tge crew at the ends or extending 100 meter tether pods before spin. The first option is arguably less complex.

 

This ONLY works if his spaceship is over 100 meters long BEFORE staging detachment.

 

If not he can't.

Problem with docking two starships like the refueling docking and spinning is that gravity will be upside down from landed configuration. 
Don't think spin gravity is really needed going to Mars with the speed run spaceX plan on. 

If so another idea is to use an cable or if that is unstable an long grinder between the two this require an nose docking port above the header tank. The grinder would still have cables for the weight the grinder is for stability. 
This might be relevant for longer missions like to the asteroids where you want to starships anyway. 
 

[RealKerbal3x]

13 hours ago, Spacescifi said:

This ONLY works if his spaceship is over 100 meters long AFTER staging detachment.

The Starship upper stage is only 50m long after stage separation. It is 120m tall at launch but the booster stage separates soon after and never actually reaches orbit.

[kerbiloid]

They should attach 50 m long arms along the Starships, rotate them by 90° and connect Starships paralelly with handshakings. Then rotate the whole thing.

[KerikBalm]

On 11/23/2020 at 9:52 AM, K^2 said:

The only place other than Earth where you can go outside briefly without a protective suit and survive is upper atmosphere of Venus, about 60km above surface. Depending on exact elevation, both temperature and pressure are comparable to what you'll find on Earth, either a bit above or a bit bellow comfortable. You will want to hold your breath and take a shower immediately after, because you'll get some sulfuric acid on you, but it's still far better than anywhere else in the Solar System. If you wanted to establish a habitat, you'll just need a thin plastic film between you and the environment to keep you safe. If there's a tear, you'll have time to locate it and fix it with some tape. And if you need to go outside to do repairs, a light hazmat suit with a rebreather and oxygen tank can have you set for hours. The only serious problems are lack of firmament to build on and difficulty in obtaining any resources you can't extract from atmosphere. That still leaves it more hospitable than surface of any body except Earth.

I was wondering if any of the gas giants would be suitable, knowing the atmosphere gets hot as you go deeper... nope:

 

Also note that Venus is quite hot at 1 Bar. At the top of Mt Everest, air pressure is 0.3 Bar, and that is quite survivable... sure going up there without O2 will lead to low level brain damage... but... thats the lack of oxygen. Venus at 0.3 Bar is not too warm at all, and inside the habitat, you can pump up the percentage of O2, so that thehab is at ambient pressure, but the residents don't suffer hypoxia.

[Hannu2]

7 hours ago, KerikBalm said:

I was wondering if any of the gas giants would be suitable, knowing the atmosphere gets hot as you go deeper... nope:

 

Also note that Venus is quite hot at 1 Bar. At the top of Mt Everest, air pressure is 0.3 Bar, and that is quite survivable... sure going up there without O2 will lead to low level brain damage... but... thats the lack of oxygen. Venus at 0.3 Bar is not too warm at all, and inside the habitat, you can pump up the percentage of O2, so that thehab is at ambient pressure, but the residents don't suffer hypoxia.

As far as I know humans can handle some level of overpressure long times if partial pressure of oxygen is corrected to about 0.2 bar. There seems to be nice temperature on Jupiter at about 5 bar level. I do not know how long it would be tolerable and there may also be toxic compounds at deep Jupiter's atmosphere so protective suit would probably be necessary.

[K^2]

8 hours ago, KerikBalm said:

I was wondering if any of the gas giants would be suitable, knowing the atmosphere gets hot as you go deeper.

Every atmosphere is a little different due to composition, but the general trends are similar, and you can see it on the graph you posted. If anything survivable would produce enough temperature difference to give you habitable climate in atmospheres of gas giants, you'd get cooked on Earth at 1 bar.

That said, keeping a large habitat warm isn't that hard, so we can still, theoretically, have cloud stations on Saturn, Uranus, and Neptune. Jupiter's "surface" gravity is a bit too high, so that one's out, I'm afraid. The main difference with Venus is that as stated earlier, you can briefly survive outside on Venus without protective gear, greatly increasing safety of any colony there, and there are ways of making Venus colony self-sufficient in the long run, because as hellish as surface conditions are, robotic mining isn't completely out of question, and you only need a balloon to lift cargo from surface to the colony. There's also plenty of sulfuric acid at lower altitudes, which can be reprocessed into water. In contrast, gas/ice giants are unlikely to be good for anything other than satisfying our scientific curiosity.

[KerikBalm]

13 hours ago, K^2 said:

There's also plenty of sulfuric acid at lower altitudes, which can be reprocessed into water. In contrast, gas/ice giants are unlikely to be good for anything other than satisfying our scientific curiosity.

That sufuric acid has very very very low water content. Venus is severely water deficient (see the thread about possible life/phosphine in the Venusian clouds), I doubt it.

As for the gas giants, well, if you had a super-duper fusion reactor, you could fuse the hydrogen and helium into heavier elements. A CNO fusion cycle perhaps, you can make a lot of structures with various carbon polymers... but even fusing to Iron, much less heavier elements, assumes a very very powerful fusion reactor.

Gas giants are most useful as hydrogen and helium sources, best taken by an orbiting spacecraft skimming hydrogen/helium off the top.

14 hours ago, Hannu2 said:

As far as I know humans can handle some level of overpressure long times if partial pressure of oxygen is corrected to about 0.2 bar. There seems to be nice temperature on Jupiter at about 5 bar level. I do not know how long it would be tolerable and there may also be toxic compounds at deep Jupiter's atmosphere so protective suit would probably be necessary.

Indeed, but that would be a similar issue with Venus. As long as its not too toxic, then a facemask with a decent seal is all you'd need.

As for Jupiter,You'd also have to worry about decompression sickness if your habitat ascends, or you ever want to leave jupiter (or your spacecraft needs to be pressurized to 5 bar, requiring more dry mass, making getting away from jupiter even harder). I'm pretty sure hydrogen gas is not toxic, like N2, Helium certainly isn't. I don't know about the other traces, I think Ammonia is in there too though, which isn't great...

You'd have to adjust the gas composition that you breathe, but it shouldn't be too different from scuba diving. At 40 meters below the ocean's surface, the pressure is already roughly 5 bar. 

https://space.stackexchange.com/questions/10895/maximum-survivable-atmospheric-pressure#:~:text=The maximum pressure for long,therefore is about 2.5 bar.

Quote

... long term survival in an atmosphere of 79 % nitrogen and 21 % oxygen is limited by oxygen toxicity. [...] the maximum pressure therefore is about 2.5 bar. For only some hours the pressure may be 4 to 5 bar, but nitrogen narcosis might be a problem. [...] For higher pressures the amount of oxygen and nitrogen in the mix must be reduced and replaced by helium. For a total pressure of 5 bar, the amount of oxygen should be not more than 4.2 % but not less 3.2 %. The partial pressure of oxygen is then again 0.21 bar like that of normal air.
For deep sea saturation diving, a pressure of about 60 bar was survived for weeks in an atmosphere of oxygen and helium.

Plenty of Helium available on Jupiter... so yea, a hab at 5 Bar, with a breathing gas composition of mainly helium with about 4% O₂ would let you go outside... but....

Buoyancy of the hab would be a big problem though... trying to float in an atmosphere of mainly hydrogen and 10% helium? You'd need to float not by having a lower average molecular weight gas, but by having a warmer gas. If you've got a fusion reactor, there's plenty of fuel for it, and you can heat it indefnitely.

The question then is how much would you need to heat the habitat's gas envelope? would you have a seperate heated envelope for buoyancy, such that the hab is at an altitude where you can go outside comfortably, or do you heat the atmosphere and internal volume of the habitat to produce buoyancy... what sort of temperature differential would you need, could you keep the hab at a relatively comfortable 27C (300K), and be able to float in a region of the atmosphere that still alows you to go outside and not freeze/have the problems of being on Titan? The denser the atmosphere, the more that cold temperature is going to freeze you faster.

I guess I'd put the limit for an acceptable outside temperature as a first guess at -20 C. Bundle up... 

So, next question, how much buoyancy would you get from  each m³ of a 96.5% H₂, 3.5% O₂ atmosphere at 300K and 5 Bar, vs a 90% H₂, 10% He atmosphere at 253K and 5 bar? I could do the math, but don't want to right now :p

 

On 11/17/2020 at 1:50 AM, Spacescifi said:

For example, if we had1g constant acceleration spacecraft

Oh geez, you must mention such a spacecraft in like 75% of your posts in this subforum

On 11/17/2020 at 1:50 AM, Spacescifi said:

flying from orbital velocity onwards at 1g for 20 min and then stalled acceleration, it's top speed will be I am betting higher than orbiting craft, but it will no longer be in a stable orbit eitherand likely will fly off into deep space unless it retroburn to slow for orbit again.

What? that sentence seems incomprehensible to me. Could you rephrase it?

On 11/17/2020 at 1:50 AM, Spacescifi said:

Orbit is only faster in that one can go in a circle faster, yet at higher orbits it takes much longer to fly in a circle.

What? that sentence seems incomprehensible to me. Could you rephrase it?

On 11/17/2020 at 1:50 AM, Spacescifi said:

Go too fast and you shoot off like a rock from slingshot in a straight line.

Yes, I agree with that analogy

On 11/17/2020 at 1:50 AM, Spacescifi said:

Orbiting is not unlike how a fast plane makes a wide circle and a slow one makes a tight one.

I don't think that's a good analogy, because with orbits the spacecraft doing the tighter circle is also the one moving faster. The spacecraft doing the wide circle (high SMA, low eccentricity orbit) is moving slower.

You temporarily speed up (+ delta V) to go to a higher orbit, but end up going slower. A one time increase in speed raises apoapsis (raises SMA, raiss eccentricity), resulting in your craft sometimes moving faster than before (at Pe) and sometimes moving slower (at Ap), and always taking longer to complete an orbit (because SMA is higher).

I don't think that translates well into an analogy of a plane turning.

Edited December 4, 2020 by KerikBalm

[K^2]

3 minutes ago, KerikBalm said:

That sufuric acid has very very very low water content.

Sulfuric acid IS water. It's SO3 + H20, and all it takes to separate them out is a bit of heat. Sulfuric acid is unstable at temperatures above 300°C.

7 minutes ago, KerikBalm said:

Plenty of Helium available on Jupiter... so yea, a hab at 5 Bar, with a breathing gas composition of mainly helium with about 4% O₂ would let you go outside... but....

At 24.8m/s², though? It's survivable short term for sure, and a healthy human will be able to walk around with effort, but I kind of suspect long-term health will be a problem. And launching from that altitude? Even how? You need something like 90km/s to make low orbit from 5bar altitude. I don't think we have a theoretical proposal for a type of engine that can achieve this ascent. Yeah, you can have a high altitude way-station, but that's probably where most of your facilities will end up, then.

If you really want to stick around gas giants, you want to stay high in atmosphere, where you still have a chance of reaching orbit, and then there is just no reason to go with Jupiter, as Saturn gives you all the same things at comfortable gravity and much cheaper ascent to orbit. From upper atmosphere it's about 43-ish km/s for Jupiter and 25-ish for Saturn. The later is still excessive, but I can at least picture some ways to achieve it without going total sci-fi.

[KerikBalm]

2 hours ago, K^2 said:

Sulfuric acid IS water. It's SO3 + H20, and all it takes to separate them out is a bit of heat. Sulfuric acid is unstable at temperatures above 300°C.

Yes, you can't have acid without water, this gives the details that I was referring to: https://www.liebertpub.com/doi/full/10.1089/ast.2020.2244

Quote

The droplets are mostly H₂SO₄ (85% by volume, on average) with a much smaller component of liquid water (15%). The droplets in the clouds of Venus do have a varying composition from ∼75% H₂SO₄ at high altitudes to ∼110% (i.e., H₂SO₄ with 10% SO₃) at the cloud base (Titov et al., 2018) after (Hoffman et al., 1980; James et al., 1997). This is in equilibrium with the water vapor in the atmosphere. The activity of water in the droplets is very low, however, because the water is tightly bound to sulfuric acid molecules. The abundance of water as a function of altitude is poorly constrained by kinetic models, but it is in the low ppm range

 

2 hours ago, K^2 said:

At 24.8m/s², though?

Yea, I meant to end my post with: "dat gravity tho..." but I forgot by the time I was done with the gas discussion :p

[kerbiloid]

4 hours ago, KerikBalm said:

I'm pretty sure hydrogen gas is not toxic

I'm not. It's a strong reducing agent and will probably cause issues in wet and hollow parts of the body being exposed for a long time. Say, mouth & teeth.

***

About Saturn

 

 

[KerikBalm]

https://www.nature.com/articles/s41598-018-38180-4

I can't find anything about long term effects of large amounts of hydrogen gas, its clearly not noxic in small quantities... 

but I missed one really obvious thing.... and a large reason why you'd never be living in a dense hydrogen atmosphere for long periods of time:

https://www.nap.edu/read/12032/chapter/9#152

Quote

At very high concentrations in air, hydrogen is a simple asphyxiant gas because of its ability to displace oxygen and cause hypoxia (ACGIH 1991). Hydrogen has no other known toxic activity. This profile considers only hydrogen gas and excludes health effects associated with other isotopic forms (deuterium or tritium) and hydrogen-containing chemicals (Windholz et al. 1976). Hydrogen-induced asphyxiation may occur at lower hydrogen concentrations when oxygen concentrations are also reduced as onboard a submarine. However, hydrogen concentrations needed to induce hypoxia even in a low-oxygen environment would far exceed the explosive limit of the gas. Thus, occupational exposure standards are set on the basis of the explosivity of hydrogen rather than its toxicity.

Mixing hydrogen and oxygen in your habitat is a bad idea, even at just 4% oxygen (and 5 Bar!).

So that leaves Helium... which means that you will need a very big temperature differential to float.

Saturn is a similar situation.

Yea, you're not going outside while floating in gas gianst, I guess.

Edited December 4, 2020 by KerikBalm

[cubinator]

I wouldn't even want to go near Jupiter because of the radiation. 

[adsii1970]

3 minutes ago, cubinator said:

I wouldn't even want to go near Jupiter because of the radiation. 

Heh... yeah.

Saturn is the flattest planet. Its polar diameter is 90% of its equatorial diameter, this is due to its low density and fast rotation. Saturn turns on its axis once every 10 hours and 34 minutes giving it the second-shortest day of any of the solar system’s planets.

[KerikBalm]

1 hour ago, cubinator said:

I wouldn't even want to go near Jupiter because of the radiation. 

The clouds would be quite safe, from radiation anyway

[KerikBalm]

*edit* oops, forgot what the thread title was: its not science and spaceflight facts, its just space facts

Anyway, back to the main topic:

Earth's life used to be mainly purple

Our cold blooded semi-aquatic Crocodiles come from warm blooded fast terrestrial ancestors with a 4 chamber heart.

There was probably pre- cellular life without DNA.

We can't really construct any good phylogenetic trees for most of the viruses, and we don't know how they came about likely multiple independent events- but there is a good chance that some come from lineages that predate cellular life

 

 

 

 

 

 

Edited December 4, 2020 by KerikBalm

[K^2]

6 hours ago, KerikBalm said:

Yes, you can't have acid without water, this gives the details that I was referring

That is completely irrelevant. We aren't talking about watering plants wit sulfuric acid mist. Activity of water in that state doesn't matter.

We are talking about collecting sulfuric acid from clouds, heating it up to high temperature, until all sulfuric acid breaks down, and separating H2O vapor from SO3. Then condencing water vapor to clean water.

Again, having sulfuric acid is as good as having water, because chemically, it is water with some junk you don't want. Just a few hoops to jump through. And there is enough sulfuric acid to make clouds.

[DerkyJerkyWreaksHavoc]

Fat earth isn't Flat

[KerikBalm]

11 hours ago, K^2 said:

That is completely irrelevant. We aren't talking about watering plants wit sulfuric acid mist. Activity of water in that state doesn't matter.

...

Again, having sulfuric acid is as good as having water, because chemically, it is water with some junk you don't want. Just a few hoops to jump through. And there is enough sulfuric acid to make clouds.

Well, my point is that while there is water there, you will need to process a lot of atmosphere to get a small amount of it.

I am not saying that it is inaccessible, just that there is not that much per unit volume

[Ikkjot]

I don't know if this is either weird or shocking but the fact is: Space is completely silent 

Its weird for me because here there is almost no silence even at night. Also for you people who know this and think its not really weird it is for me. for some reason

Edited December 5, 2020 by Ikkjot

[sir rocket]

10 hours ago, Ikkjot said:

Its weird for me because here there is almost no silence even at night. Also for you people who know this and think its not really weird it is for me. for some reason

I don't think it would feel completely silent. Your brain would try to fill in sounds for the deprivation, causing a ringing. Note that this is from personal experience, not any scientific studies