For Questions That Don't Merit Their Own Thread

[magnemoe]

8 hours ago, Shiki404 said:

Does the amount of colonist needed different between planetary-based colony and orbital-based space colony? Assuming the necessities such as food, life support, basic services and healthcare etc. is already fulfilled, what's the minimum amount of colonist needed in order to create a stable and growing population?

Now biological  @monophonic answered that well. So it would be true on an remote island. 
But if you think about an totally independent space station or base it would need to repair and replace all the systems needed for maintenance and life support long term. So space suits or remote operated robots for working in vacuum and the machines for creating this, and the machines for creating them and so on, all the way down to mining the resources. 

[JoeSchmuckatelli]

9 hours ago, Shiki404 said:

Does the amount of colonist needed different between planetary-based colony and orbital-based space colony? Assuming the necessities such as food, life support, basic services and healthcare etc. is already fulfilled, what's the minimum amount of colonist needed in order to create a stable and growing population?

Monophonic's answer is solid:

7 hours ago, monophonic said:

The long term threats are major catastrophies and inbreeding

The other search term is genetic drift. 

https://www.pbs.org/wgbh/evolution/library/06/3/l_063_03.html

https://www.cam.ac.uk/research/news/direct-genetic-evidence-of-founding-population-reveals-story-of-first-native-americans

Finally, there is the risk of being separate from the rest of humanity for too long (c.f. Native American population collapse).  

 

Side fact - all Native American population had Type O blood 

Edited November 23, 2023 by JoeSchmuckatelli

[SunlitZelkova]

On 11/22/2023 at 8:57 PM, Shiki404 said:

Does the amount of colonist needed different between planetary-based colony and orbital-based space colony? Assuming the necessities such as food, life support, basic services and healthcare etc. is already fulfilled, what's the minimum amount of colonist needed in order to create a stable and growing population?

It would be the same regardless of if it is surface or orbital.

Different studies have been undertaken but no one knows. The estimates range from 14 to 15,000.

[SunlitZelkova]

Do direct descent trajectories to the Moon cost more delta v at landing than stopping in orbit?

I have been thinking about the Constellation program, and realized the Ares V would probably need to launch a “doggy” lander that sits on its butt during launch to land a big rover. Like this.

(This thing made sense with Shuttle-C or Energia loads slung over the side, but with Ares V it would be odd to mount) Also I couldn’t find info on if the particular lander below was a direct descent or not but it is possible it was.

But it doesn’t seem like this thing would have the delta v to stop in orbit and then deorbit, especially considering normally the Altair was responsible for doing these things and there would be no room for an Altair derived upper stage below the Ares V Earth Departure stage. So the doggy lander would be on its own.

Obviously, the Altair was not really a good vehicle to convert into a vehicle transport lander. It was pretty darn tall.

[Terwin]

2 hours ago, SunlitZelkova said:

Do direct descent trajectories to the Moon cost more delta v at landing than stopping in orbit?

By direct descent, I assume you are referring to reducing your pe until it intersects the surface then doing a suicide burn to land.

This costs dv for your orbital velocity plus increasing gravity losses as you slow down to land.

Stopping in orbit s much the same, you spend dv to cancel your orbital velocity, then you need to pay increasing gravity losses as you slow to a stop.  But then you get to pay dv to cancel the acceleration due to gravity between the time you stop your orbit and the time you land.

In theory, these can be very similar amounts of dv if you are orbiting just above the surface, but generally speaking paying gravity losses for longer than you need to is bad for your dv budget.  As such, 'stopping in orbit' is only viable if gravity losses are trivial, such as when landing on Gilly.

[SunlitZelkova]

2 hours ago, Terwin said:

By direct descent, I assume you are referring to reducing your pe until it intersects the surface then doing a suicide burn to land.

This costs dv for your orbital velocity plus increasing gravity losses as you slow down to land.

Stopping in orbit s much the same, you spend dv to cancel your orbital velocity, then you need to pay increasing gravity losses as you slow to a stop.  But then you get to pay dv to cancel the acceleration due to gravity between the time you stop your orbit and the time you land.

In theory, these can be very similar amounts of dv if you are orbiting just above the surface, but generally speaking paying gravity losses for longer than you need to is bad for your dv budget.  As such, 'stopping in orbit' is only viable if gravity losses are trivial, such as when landing on Gilly.

By direct descent, I mean a one way version of a direct ascent profile. For example, the original monolithic Apollo spacecraft and Chelomei’s LK-700 Moon lander were not intended to brake into lunar orbit after coasting to the Moon. They would perform course correction maneuvers along the way and aim directly for their landing site, so instead of braking into lunar orbit, they basically fly the same trajectory a lunar impact or (like Ranger 7) would fly and then soft land on the surface.

Such a flight profile allows travel to anywhere on the near side of the Moon, whereas the Apollo spacecraft we got was limited to the equatorial regions due to having to have the CSM always be in a position so that the LM could liftoff and rendezvous at any stage of the mission in the event of an abort.

I’m actually now realizing any rover carrier lander probably would need to brake into lunar orbit, because the Constellation lunar base was supposed to be on the South Pole of the Moon.

So here is another question (for anyone)- do you have to enter a lunar orbit to get to the South Pole (like Shackleton Crater) or could you do a direct descent/direct ascent style mission to it?

[JoeSchmuckatelli]

23 minutes ago, SunlitZelkova said:

for anyone

My 'used to play KSP' answer is... sure?  

Given enough deltaV I'm pretty sure you could do a mid-course correction on an intercept to get a craft aimed at the pole and then suicide burn to a halt wherever you wanted.  (I was never good enough to hit anything other than 'an orbit')

Which - now that I think about it - might be the same amount of fuel you would need to do an inefficient orbital capture, followed by changing inclination to polar followed by lowering PE to intercept.  (Someone will, of course, point out that I have no idea what I'm talking about via fuel needs... but then again, I am the resident knuckle dragger!)

[kerbiloid]

You may need a standby orbit to wait for a good lunar weather for landing.

Stormy lunar seas, clouds, solar winds, sometimes tornados.

[magnemoe]

On 11/24/2023 at 11:23 AM, SunlitZelkova said:

It would be the same regardless of if it is surface or orbital.

Different studies have been undertaken but no one knows. The estimates range from 14 to 15,000.

Note that this is true for all isolated populations so an island or simply being cut of from rest of species count. 15000 is way to high yes it give an good buffer. 500 is probably enough but it put you on the threatened list of species. 14 and you have serious problems. 

[JoeSchmuckatelli]

4 hours ago, magnemoe said:

Note that this is true for all isolated populations so an island or simply being cut of from rest of species count. 15000 is way to high yes it give an good buffer. 500 is probably enough but it put you on the threatened list of species. 14 and you have serious problems. 

Yeah - I've seen reports that the primary population of the indigenous people who first settled the Americas (N&S) was possibly as low as 3500 individuals (genetic extrapolation). 

Certainly the next several thousand years proved them to be resilient and sufficient for the various environments - but being cut off from the rest of humanity, very very few domestic animals and no understanding of infection /  germ theory in the world did not help. 

Possible that future colonists could be OK even if cut off for thousands of years - presuming no major loss of technology / information about disease management upon reconnecting with disparate populations, etc. 

Edited November 30, 2023 by JoeSchmuckatelli

[darthgently]

3 hours ago, JoeSchmuckatelli said:

Yeah - I've seen reports that the primary population of the indigenous people who first settled the Americas (N&S) was possibly as low as 3500 individuals (genetic extrapolation). 

Certainly the next several thousand years proved them to be resilient and sufficient for the various environments - but being cut off from the rest of humanity, very very few domestic animals and no understanding of infection /  germ theory in the world did not help. 

Possible that future colonists could be OK even if cut off for thousands of years - presuming no major loss of technology / information about disease management upon reconnecting with disparate populations, etc. 

There has been discussion for awhile that a distant colony might need periodic introduction of the latest strains of the common cold, flu, etc to keep immunity in sync

[Shiki404]

In a lot of medias, whenever there's a planetary-based colony, there's a high probability that asteroid strikes is mentioned as a major hazard for the colony (especially if the colony's celestial body has little to no atmosphere). In a lot of them the solution is either have a network of guns to destroy the object or in more softer sci-fi, an bubble of energy shield

But in real life, what'll be a realistic measure to handle such a threat? Assuming there's an asteroid big enough to threaten a colony by causing major damage to infrastructure, what solution that's most likely being implemented in real life? Shoot it with ground-based gun? Launch a missile to divert it's trajectory? Attach probes on it with thrusters to divert it? Or what? (energy shield is obviously not in the option)

[kerbiloid]

To not found colonies on the airless bodies.

Also, "airless" == "low gravity", what is also not healthy.

[DDE]

1 hour ago, Shiki404 said:

Launch a missile to divert it's trajectory?

This one's probably closest to the grasp of current technology, although asteroids are a far, far faster target than other missiles.

[Shiki404]

1 hour ago, kerbiloid said:

To not found colonies on the airless bodies.

Also, "airless" == "low gravity", what is also not healthy.

Some place like our own moon is too good to pass up as a hub for further space missions

[monophonic]

2 hours ago, Shiki404 said:

In a lot of medias, whenever there's a planetary-based colony, there's a high probability that asteroid strikes is mentioned as a major hazard for the colony (especially if the colony's celestial body has little to no atmosphere). In a lot of them the solution is either have a network of guns to destroy the object or in more softer sci-fi, an bubble of energy shield

But in real life, what'll be a realistic measure to handle such a threat? Assuming there's an asteroid big enough to threaten a colony by causing major damage to infrastructure, what solution that's most likely being implemented in real life? Shoot it with ground-based gun? Launch a missile to divert it's trajectory? Attach probes on it with thrusters to divert it? Or what? (energy shield is obviously not in the option)

Sufficiently spaced out network of individual habitats and evacuations of threatened ones. I.e. how we manage predictable disasters here on Earth right now. Hurricane heading towards Florida? Evacuate. Volcano getting ready to erupt under Grindavik? Evacuate. Asteroid on course to hit Hellas City? Evacuate.

There has been a lot of talk about potential methods to deflect threatening asteroids. The problem is that all the feasible ones have to be implemented a long time before inevitability of impact becomes apparent. That means sufficient funding is unlikely to be allocated in time to be effective. Improving technology will eventually change that, but there is still a long way to go.

[JoeSchmuckatelli]

 

 

 

 

[kerbiloid]

Yes. Lasers.
 

Spoiler

Dieter Laser's.

 

 

 

 

[magnemoe]

On 11/29/2023 at 3:55 AM, SunlitZelkova said:

By direct descent, I mean a one way version of a direct ascent profile. For example, the original monolithic Apollo spacecraft and Chelomei’s LK-700 Moon lander were not intended to brake into lunar orbit after coasting to the Moon. They would perform course correction maneuvers along the way and aim directly for their landing site, so instead of braking into lunar orbit, they basically fly the same trajectory a lunar impact or (like Ranger 7) would fly and then soft land on the surface.

Such a flight profile allows travel to anywhere on the near side of the Moon, whereas the Apollo spacecraft we got was limited to the equatorial regions due to having to have the CSM always be in a position so that the LM could liftoff and rendezvous at any stage of the mission in the event of an abort.

I’m actually now realizing any rover carrier lander probably would need to brake into lunar orbit, because the Constellation lunar base was supposed to be on the South Pole of the Moon.

So here is another question (for anyone)- do you have to enter a lunar orbit to get to the South Pole (like Shackleton Crater) or could you do a direct descent/direct ascent style mission to it?

Who is correct but the mass penalty of landing  the heavy capsule you will reenter in adds  an serious mass penalty, you would need an larger rocket than Saturn 5 to pull that off. 

[SunlitZelkova]

7 hours ago, magnemoe said:

Who is correct but the mass penalty of landing  the heavy capsule you will reenter in adds  a serious mass penalty, you would need a larger rocket than Saturn 5 to pull that off. 

The lander design I am asking about for this trajectory is uncrewed and one way. It’s a cargo lander.

[Shiki404]

If humans have mastered capabilites to mine resources from space, what kind of resources in our solar system that's worth to be mined, especially on some planets/ moons that could serve as the primary source of such endeavor? (Assuming we're already advanced enough to do regular interplanetary travel with permanent colonies beyond Earth orbit)

[kerbiloid]

Hypothetical lantanoid and platinoid deposits in large impact craters on the Moon and Psyche.

Actually, almost everything useful and available Is stored here, on the Earth.

[darthgently]

25 minutes ago, kerbiloid said:

Actually, almost everything useful and available Is stored here, on the Earth.

True, but the earth-gravity-well cost figures in as does dv cost to location of use generally.  If the use is on Earth, then the case for space-mined resources diminishes.  If the use is dv-near the mining site that changes things.  So a lot depends on where we plan to use stuff

[JoeSchmuckatelli]

Got something for you Math Nerds:

Does the windshield of a car travelling at 60 mph hit more raindrops in one second than the windshield of the same model parked collects?

Spoiler

FWIW - I tried to figure this out; 

• at 60mph, the windshield travels at 88 feet per second.
• raindrop terminal velocity is about 32 feet per second
• 2 foot tall windshield at 45 degrees has a surface area...
• math something
• volume
• dis...
• ...
• ask the smart guys.

•  

[SunlitZelkova]

10 hours ago, Shiki404 said:

If humans have mastered capabilites to mine resources from space, what kind of resources in our solar system that's worth to be mined, especially on some planets/ moons that could serve as the primary source of such endeavor? (Assuming we're already advanced enough to do regular interplanetary travel with permanent colonies beyond Earth orbit)

Basically the stuff you find on Earth, except in higher quantities because of how many asteroids there are.

Things like lithium would be in high demand because of their rarity on Earth and how important they are in manufacturing semi-conductors.