For Questions That Don't Merit Their Own Thread

[JoeSchmuckatelli]

1 hour ago, Terwin said:

All biologically generated proteins on earth are right handed proteins, some inorganic processes create both right and left hand proteins, and left hand proteins are highly toxic. 

If the new planet uses left handed proteins, then even if they are otherwise identical to us(which I suspect may not be possible), they will be 100% toxic to us and we will be 100% toxic to them.

(might have the right and left swapped, but the principal is the same regardless)

Ah yes - Chirality... Something I forgot about. 

 

According to this, however, I think it is Left Handed Proteins 

"Life on Earth is made of left handed amino acids, almost exlusively.'

https://www.vanderbilt.edu/AnS/physics/astrocourses/ast201/aastruct.html#:~:text=Amino Acid Structures&text=Anything that has both is an amino acid.&text=An interesting aspect of most,these molecules formed in space.

Interesting to note that they think that the handedness of the amino acids and proteins may originate in space... Thus the extent to which Pan Spermia is a real thing - and if so, whether it is universal or local should be determinative. 

 

Interesting to think about - were we to discover a right handed (protein) alien civ... We might be able to get along with them as we would be competing for mutually exclusive resources... But any left handed civs better watch out! 

[kerbiloid]

6 hours ago, Terwin said:

All biologically generated proteins on earth are right handed proteins, some inorganic processes create both right and left hand proteins, and left hand proteins are highly toxic. 

And all of them can be turned into ammonia and methane in a compost vat to build the proper ones out of this fertilizer.

The question should be more clear: "can we eat them directly" or "can we consume them as food"..

  

5 hours ago, JoeSchmuckatelli said:

Interesting to note that they think that the handedness of the amino acids and proteins may originate in space...

The world made of usual matter is L-R asymmetrical, at least because neutrinos and antineutrinos have opposite spins, and a neutron decay creates antineutrinos, so their amount is not equal.

So, this is a question of "where is all that antimatter?"

Edited February 1, 2021 by kerbiloid

[ARS]

Why the design for reentry vehicle is always smooth-curved (like the underside of space shuttle or the design of Apollo/ Soyuz capsule). What if the reentry capsule/ vehicle design itself is viable for reentry but with highly angular design? (aka, same design, but all smooth and curved part is turned into blocky angular), compare Apollo/ Soyuz capsule with WH40k space marine drop pods

[JoeSchmuckatelli]

1 hour ago, ARS said:

Why the design for reentry vehicle is always smooth-curved (like the underside of space shuttle or the design of Apollo/ Soyuz capsule). What if the reentry capsule/ vehicle design itself is viable for reentry but with highly angular design? (aka, same design, but all smooth and curved part is turned into blocky angular), compare Apollo/ Soyuz capsule with WH40k space marine drop pods

Probably for the same reason that plane wings have a smooth leading edge.  Blocky shaped wing surfaces sound like a recipe for unexpected vortices / drag and lift characteristics 

 

 

 

 

... 

 

 

 

Edit - here is a fun (non sequitur) tidbit I ran across in Smithsonian "The first modern antidepressants were originally tuberculosis medications, created from leftover World War II rocket fuel. " 

 

--now we know why the Kerbils are so happy... They're sampling the fuel! 

Edited February 1, 2021 by JoeSchmuckatelli

[kerbiloid]

The edges and corners will overheat.

[RyanRising]

2 hours ago, ARS said:

Why the design for reentry vehicle is always smooth-curved (like the underside of space shuttle or the design of Apollo/ Soyuz capsule). What if the reentry capsule/ vehicle design itself is viable for reentry but with highly angular design? (aka, same design, but all smooth and curved part is turned into blocky angular), compare Apollo/ Soyuz capsule with WH40k space marine drop pods

To expand on that “the edges will overheat” thing, in this video Scott Manley mentions that the shock wave generated by a curved body maintains a distance roughly proportional to the radius of the curve. The shock wave is where the highest temperatures and pressures occur, so you want to keep it as far away from your spacecraft as you can. If you make the curve tighter (eventually leading to sharp edges like you mention) you decrease the radius of that curve, which brings the shock wave closer in to the body, exposing it to more heat. 

[DDE]

On 2/1/2021 at 4:27 PM, RyanRising said:

To expand on that “the edges will overheat” thing, in this video Scott Manley mentions that the shock wave generated by a curved body maintains a distance roughly proportional to the radius of the curve. The shock wave is where the highest temperatures and pressures occur, so you want to keep it as far away from your spacecraft as you can. If you make the curve tighter (eventually leading to sharp edges like you mention) you decrease the radius of that curve, which brings the shock wave closer in to the body, exposing it to more heat. 

Yes, it's a good thing to remember that this is compression heating, not friction heating.

Edited February 2, 2021 by DDE
A letter

[magnemoe]

On 2/1/2021 at 1:28 AM, JoeSchmuckatelli said:

Ah yes - Chirality... Something I forgot about. 

 

According to this, however, I think it is Left Handed Proteins 

"Life on Earth is made of left handed amino acids, almost exlusively.'

https://www.vanderbilt.edu/AnS/physics/astrocourses/ast201/aastruct.html#:~:text=Amino Acid Structures&text=Anything that has both is an amino acid.&text=An interesting aspect of most,these molecules formed in space.

Interesting to note that they think that the handedness of the amino acids and proteins may originate in space... Thus the extent to which Pan Spermia is a real thing - and if so, whether it is universal or local should be determinative. 

 

Interesting to think about - were we to discover a right handed (protein) alien civ... We might be able to get along with them as we would be competing for mutually exclusive resources... But any left handed civs better watch out! 

And ninjaed an long time ago.
http://freefall.purrsia.com/ff800/fv00710.htm

Edited February 2, 2021 by magnemoe

[The Blazer]

What do you guys think it is the best way to get out of Venus (in real life)? I’m thinking some sort of multi-stage rocket powered spaceplane, that it uses the atmosphere to climb until a point where the atmospheric pressure, temperature and drag is similar to Earth’s (maybe less) then detach the orbital vehicle. 

[K^2]

1 hour ago, The Blazer said:

What do you guys think it is the best way to get out of Venus (in real life)? I’m thinking some sort of multi-stage rocket powered spaceplane, that it uses the atmosphere to climb until a point where the atmospheric pressure, temperature and drag is similar to Earth’s (maybe less) then detach the orbital vehicle. 

That's a non-starter. First of all, in lower Venusian atmosphere, rockets are just a bad idea. If you want a plane to do initial climb, it will have to be propeller driven. And that can get you to altitudes with similar conditions to airliners, albeit, at lower speeds. And note that we don't launch rocket planes from these altitudes either. We go for regular old rockets. You just don't get much benefit from wings if your propulsion system is a rocket. Can you builds a prop plane that launches an orbit capable rocket on Venus? Maybe? But it seems like a very inefficient way to go about it.

If our goal is something like sample return, I would propose one of two solutions. First option, we land a rocket on parachutes, then lift it with balloons into as thin atmosphere as we can, then do conventional launch. The downside is landing a rocket on Venus. Building tanks that will survive the landing is going to be extremely difficult. So would building electronics that can manage all of that and survive the temperatures. So while the mission profile here is simple, I'm worried it will stretch our material science to the limit. Or past it.

The second option is rendezvous. You drop a dumb lander. It scoops up dirt and fires gas generator canisters that inflate balloons. This can all be done with zero circuitry if needed, using clockwork. Now the goal is to meet up with the rocket in upper atmosphere. You probably want to have a space plane re-enter but keep going at hypersonic speeds in really thin atmosphere, so your sample return will have to match speeds. That can be achieved with a simple solid state motor and a simple guidance system, though, leaving the job of precise maneuvering for pickup to the space plane. Once the payload is picked up, the main rocket is fired and the rest continues similar to launch from high altitude aircraft. This kind of mission will require good timing and very precise maneuvering, but it's something we know how to do. So I think it's the more plausible of the two.

The only good news in all of this is that unlike Eve, Venus has a slightly lower gravity, so at least the orbital velocity you need to achieve isn't as high. But it's still something you have to get exceptionally creative with to have a chance to pull it off.

[kerbiloid]

4 hours ago, The Blazer said:

What do you guys think it is the best way to get out of Venus (in real life)? I’m thinking some sort of multi-stage rocket powered spaceplane, that it uses the atmosphere to climb until a point where the atmospheric pressure, temperature and drag is similar to Earth’s (maybe less) then detach the orbital vehicle. 

Quote

As of January Raptor also produces the highest combustion chamber pressure ever reached by an operational rocket engine, at 330 bar (33,000 kilopascals), surpassing the record held by the RD-701 rocket engine at 300 bars.

The Venus pressure is ~90 bar.

So, by using an engine with highest possible exhaust pressurem of course, you still can use rockets to start from Venus.
Just first 20 km of altitude they will be twice less efficient, so you nee large tanks.

The tanks can be made of thin aluminium, no problem with pressure at all.
You just should use a valve with freely moving piston to keep the internal pressure equal to the external one,
As aluminium (and other typical construction metals) usually have ~200 MPa (2 000 bar) strength limit, you don't need to care about the 90 bar stress at all.

(On the Earth they don't need this because it's easier to just make thicker walls, which are anyway required to withstand the static pressure of fuel inside.
Say, the tank height is ~20 m, fuel density ~1 t/m³, initial overload 2 g, so the static pressure ~20 * 1 000 * 9.81 * 2 / 100 000 ~= 4 bar).

The larger are the fuel tanks, the slower they are warming (because of total heat capacity, and lower surface-to-volume ratio).
So, enough large landed rocket (and you need a large one to reach the orbit) should withstand several hours on surface without active cooling.
Though, if you use cryogenic components (and probably, so), use a turboexpander to heat the carbon dioxide from 480°C to 800°C and exhaust it with the heat waste.

Of course, the tank should have a rotating skimmer inside (like Buran had), to prevent local fuel heating.

Put your command pod and upper stage with simple tanks into a strong shell to withstand the external pressure, keeping low pressure inside.
Jettison the shell halves  once you reach several tens km altitude to drop excessive mass.

***

Of course don't use mechanical parts like propellers just because you need a heavy rocket to launch the orbit, so the propellers should be of enormous diameter and the blades would suffer from enormous drag in the dense atmosphere.

Of course don't use balloons just because you need a heavy rocket to launch the orbit, so the balloon envelopes should be of enormous diameter and mass).

Edited February 5, 2021 by kerbiloid

[DDE]

1 hour ago, K^2 said:

If you want a plane to do initial climb, it will have to be propeller driven.

Why propellers, though? A thermal jet could probably be more efficient.

[kerbiloid]

11 minutes ago, DDE said:

A thermal jet could probably be more efficient.

Of course, you are aware that Venus doesn't have an oxidizer for free, so any jet there is a bad rocket in sense of fuel efficiency.

Edited February 5, 2021 by kerbiloid

[K^2]

19 minutes ago, DDE said:

Why propellers, though? A thermal jet could probably be more efficient.

Not even close. I'm not sure what gave you that idea. The only kind that might be even remotely viable is nuclear thermal, but you'll have a heck of a problem with waste heat. And you'll still get better TWR out of running a turbine to a prop.

Jet propulsion makes sense if you are moving fast relative to the working fluid, and that's the last thing you want on Venus. You want slow turning props that generate high thrust to pull you out of that soup. The density you're dealing with is a lot closer to that of water than that of air. And high temperature actually makes gasses more viscous. You do not want anything moving rapidly relative to the atmosphere in these conditions or that's where all the energy will end up.

Honestly, at just the intuitive level, if you are trying to come up with a plan for leaving Venusian surface, try to imagine leaving Earth, but you start inside of a vent of a volcano at the bottom of an ocean. That's a lot closer to the kinds of challenges you'll be dealing with in terms of hydrodynamics, temperature, and probably even chemical composition. The biggest difference is that there isn't a clean liquid/gas interface like you do get with the ocean, so any techniques you come up with for early ascent are going to start struggling before the techniques you'd use for late ascent become efficient. And that makes Venusian ascent extra, extra challenging.

[magnemoe]

4 hours ago, K^2 said:

That's a non-starter. First of all, in lower Venusian atmosphere, rockets are just a bad idea. If you want a plane to do initial climb, it will have to be propeller driven. And that can get you to altitudes with similar conditions to airliners, albeit, at lower speeds. And note that we don't launch rocket planes from these altitudes either. We go for regular old rockets. You just don't get much benefit from wings if your propulsion system is a rocket. Can you builds a prop plane that launches an orbit capable rocket on Venus? Maybe? But it seems like a very inefficient way to go about it.

If our goal is something like sample return, I would propose one of two solutions. First option, we land a rocket on parachutes, then lift it with balloons into as thin atmosphere as we can, then do conventional launch. The downside is landing a rocket on Venus. Building tanks that will survive the landing is going to be extremely difficult. So would building electronics that can manage all of that and survive the temperatures. So while the mission profile here is simple, I'm worried it will stretch our material science to the limit. Or past it.

The second option is rendezvous. You drop a dumb lander. It scoops up dirt and fires gas generator canisters that inflate balloons. This can all be done with zero circuitry if needed, using clockwork. Now the goal is to meet up with the rocket in upper atmosphere. You probably want to have a space plane re-enter but keep going at hypersonic speeds in really thin atmosphere, so your sample return will have to match speeds. That can be achieved with a simple solid state motor and a simple guidance system, though, leaving the job of precise maneuvering for pickup to the space plane. Once the payload is picked up, the main rocket is fired and the rest continues similar to launch from high altitude aircraft. This kind of mission will require good timing and very precise maneuvering, but it's something we know how to do. So I think it's the more plausible of the two.

The only good news in all of this is that unlike Eve, Venus has a slightly lower gravity, so at least the orbital velocity you need to achieve isn't as high. But it's still something you have to get exceptionally creative with to have a chance to pull it off.

Yes landing an rocket to the surface and then take it up with balloons is possible but as you say its will have to be an large construction. 

Another option is too drop an blimp with an rocket down into the atmosphere.  Have it drop an lander who lands do samples then use an balloon to get the samples up again. 
You can have electronic and stuff on the lander as it only need to survive an limited time. Then you need to get the blimp close to the balloon and grab the sample. 
Benefit is that here you have time. You might even use multiple landers, then done take the blimp as high as it get, fire the rocket and get it into orbit there the sample can be moved to an return module. 

[DDE]

3 hours ago, kerbiloid said:

Of course, you are aware that Venus doesn't have an oxidizer for free, so any jet there is a bad rocket in sense of fuel efficiency.

Thermal jet.

[kerbiloid]

10 minutes ago, DDE said:

Thermal jet.

Ah, i.e. nuclear.

But rocket with chemistry looks enough (though I'm totally for the atompunk, of course).

56 minutes ago, magnemoe said:

Another option is too drop an blimp with an rocket down into the atmosphere.  Have it drop an lander who lands do samples then use an balloon to get the samples up again. 
You can have electronic and stuff on the lander as it only need to survive an limited time. Then you need to get the blimp close to the balloon and grab the sample. 
Benefit is that here you have time. You might even use multiple landers, then done take the blimp as high as it get, fire the rocket and get it into orbit there the sample can be moved to an return module. 

The Venusian air is thick, so the small landers use a small disk of metal instead of a chute.

So, as you anyway have to encase the landable return vessel for aerobraking, just make the wall of the case make of sectors/petals and expand them after aerobraking for landing.

On touchdown either jettison them, or use as a part of cooling system.

Edited February 5, 2021 by kerbiloid

[K^2]

56 minutes ago, magnemoe said:

Another option is too drop an blimp with an rocket down into the atmosphere.  Have it drop an lander who lands do samples then use an balloon to get the samples up again. 
You can have electronic and stuff on the lander as it only need to survive an limited time. Then you need to get the blimp close to the balloon and grab the sample. 
Benefit is that here you have time. You might even use multiple landers, then done take the blimp as high as it get, fire the rocket and get it into orbit there the sample can be moved to an return module. 

There's definitely room for discussion here, and above is what popped into my head first, but I would still argue that sending a lander first by itself, and after the sample return portion ascends with balloon, do a fly-by to pick it up with a recovery vehicle is a better plan.

The plan you outline has two main advantages. You can, potentially, send multiple probes down, as you've said, and you also don't need to do any high speed maneuvering to collect the samples before returning. Note that in your plan, the sample return will still have to chase the main rocket. Venus has very strong winds at high altitudes and basically none at ground level. Anything that goes down and then back up is going to fall very far behind. Near equator, it might even make sense to wait for a full revolution, as it takes upper atmosphere only 96 hours to revolve around the planet. Naturally, whether you wait for a round trip or try to catch up, making way back to the main ship is going to be a huge challenge for landers.

In addition to that, you are still dealing with a giant zeppelin supporting the main rocket, which you need to deploy while descending through atmosphere within a very short window of atmospheric entry. It's far from the greatest challenge of the mission, but it's a non-trivial one, and will further reduce maneuverability of the main ship, requiring the sample return vehicles to do all the maneuvering for rendezvous.

This is precisely why I recommended sending a recovery vehicle from orbit only after sample return has ascended to high atmosphere. You can be fairly precise when coming in from orbit on where you'll meet up with the sample return, and recovery vehicle can be effectively gliding at several times the speed of sound in its vicinity without requiring much in terms of additional hardware compared to what you'd need to enter the atmosphere. So all the sample return vehicle needs is a small rocket to get up to the same speed. And since now the recovery vehicle already has a decent starting speed in relatively thin atmosphere and in lighter gravity, you are very likely to be able to get away with a relatively simple SSTO.

The downsides, of course, are that you'll very unlikely be able to collect more than a single sample return vehicle in a single pass, which almost certainly means that's the limit for the mission, and you do need to dock two vehicles traveling several times the speed of sound completely autonomously. On the plus side, the later sounds like a pure engineering challenge. So overall, this seems like the most doable thing with technology as is.

10 minutes ago, DDE said:

Thermal jet.

Any practical jet used in propulsion is a thermal jet. But yes, I've addressed nuclear thermal.

[cubinator]

16 hours ago, The Blazer said:

What do you guys think it is the best way to get out of Venus (in real life)? I’m thinking some sort of multi-stage rocket powered spaceplane, that it uses the atmosphere to climb until a point where the atmospheric pressure, temperature and drag is similar to Earth’s (maybe less) then detach the orbital vehicle. 

Send the lander up to 40-60 km with a balloon, then send it to orbit with a rocket. Don't even bother with any kind of engine below the clouds.

Edited February 5, 2021 by cubinator

[RealKerbal3x]

3 minutes ago, cubinator said:

Send the lander up to 40-60 km with a balloon, then send it to orbit with a rocket. Don't even bother with any kind of engine below the clouds.

This was actually a study NASA did for a crewed Venus mission. 

I don't think it got beyond pretty pictures and I have no idea how practical it would have been, but it's pretty cool nonetheless.

[kerbiloid]

It's an absolutely must-have  for KSP, and I hope already for several releases the next one will be "KSP 1.xx: Buoyancy" for airships and submersibles.

[cubinator]

3 minutes ago, RealKerbal3x said:

I don't think it got beyond pretty pictures and I have no idea how practical it would have been, but it's pretty cool nonetheless.

Definitely. That's a pretty small habitat though - for a little tradeoff in buoyancy, you could fill the balloon with breathing air, which floats in Venus' atmosphere, and live inside the balloon.

[The Blazer]

8 hours ago, K^2 said:

There's definitely room for discussion here, and above is what popped into my head first, but I would still argue that sending a lander first by itself, and after the sample return portion ascends with balloon, do a fly-by to pick it up with a recovery vehicle is a better plan.

The plan you outline has two main advantages. You can, potentially, send multiple probes down, as you've said, and you also don't need to do any high speed maneuvering to collect the samples before returning. Note that in your plan, the sample return will still have to chase the main rocket. Venus has very strong winds at high altitudes and basically none at ground level. Anything that goes down and then back up is going to fall very far behind. Near equator, it might even make sense to wait for a full revolution, as it takes upper atmosphere only 96 hours to revolve around the planet. Naturally, whether you wait for a round trip or try to catch up, making way back to the main ship is going to be a huge challenge for landers.

In addition to that, you are still dealing with a giant zeppelin supporting the main rocket, which you need to deploy while descending through atmosphere within a very short window of atmospheric entry. It's far from the greatest challenge of the mission, but it's a non-trivial one, and will further reduce maneuverability of the main ship, requiring the sample return vehicles to do all the maneuvering for rendezvous.

This is precisely why I recommended sending a recovery vehicle from orbit only after sample return has ascended to high atmosphere. You can be fairly precise when coming in from orbit on where you'll meet up with the sample return, and recovery vehicle can be effectively gliding at several times the speed of sound in its vicinity without requiring much in terms of additional hardware compared to what you'd need to enter the atmosphere. So all the sample return vehicle needs is a small rocket to get up to the same speed. And since now the recovery vehicle already has a decent starting speed in relatively thin atmosphere and in lighter gravity, you are very likely to be able to get away with a relatively simple SSTO.

The downsides, of course, are that you'll very unlikely be able to collect more than a single sample return vehicle in a single pass, which almost certainly means that's the limit for the mission, and you do need to dock two vehicles traveling several times the speed of sound completely autonomously. On the plus side, the later sounds like a pure engineering challenge. So overall, this seems like the most doable thing with technology as is.

Any practical jet used in propulsion is a thermal jet. But yes, I've addressed nuclear thermal.

This seems like an interesting solution. So basically you propose three vehicles: the lander that can take surface samples, the “SSTO” that meets it in the upper Venus atmospheric and the Earth return vehicle aka Apollo CSM or something like that. The only problem I see is that, as you said, there are very strong winds in the upper atmosphere, so I’m not even sure that atmospheric docking is possible.

[K^2]

24 minutes ago, The Blazer said:

The only problem I see is that, as you said, there are very strong winds in the upper atmosphere, so I’m not even sure that atmospheric docking is possible.

Earth's atmosphere is rotating significantly faster than Venus'. We just don't call that wind, because ground rotates at the same speed.

Venus' atmosphere super-rotates, but due to high density and viscosity of lower layers, any effect from difference in rotation speed between ground and atmosphere is completely nullified a few kilometers off the surface. The ground might as well not be there as far as upper atmosphere is concerned, and so the absolute wind speed is completely irrelevant.

On Earth, we're used to high turbulence, shear, and wind gusts to come with high wind speeds, because there is interaction with static terrain as well as temperature variations across it. Even on global weather scale, mountains and shapes of continents make an impact on how weather systems develop. You don't have any of that on Venus. The atmosphere is opaque, so the heat energy received by atmosphere is exceptionally uniform, and mountains are all lost in that thick, viscous part of the atmosphere, so they make absolutely no impact. The "weather" in upper Venusian atmosphere is exceptionally "calm". There is very little shear, turbulence, or gusts. Movement of atmosphere tends to be very uniform over large distances.

There's still a huge challenge in docking at hypersonic speeds. And I don't know enough about hypersonic aerodynamics to say how doable that is. Naively, I want to say that if you're catching up from behind, you should be inside the shock cones, and so it shouldn't be fundamentally different from same maneuver at subsonic speeds, but I'm not certain.

If that's not feasible, you'd have to drop speeds to subsonic and do docking the same way the in-air refueling is done. A slower start will mean extra fuel requirements, and then this might not work as an SSTO. I still think recovery vehicle should be a space plane even if it has to be staged, but it would certainly mean your recovery vehicle is larger and payload you can retrieve is smaller, which is a shame. But in any case, the absolute speed of wind with respect to terrain isn't going to matter. Conditions are going to be much better than they would have been on Earth at similar pressure altitude. The only thing that matters is how fast you're moving through local atmosphere during the docking.

[JoeSchmuckatelli]

If they were able to get a blimp into the atmosphere and just let it fly around for a while - the science could be astounding. 

 

And why bother with a lander / rover.  Just drop a weighted bucket on a cable and scrape up the top layer.  On board equipment in the gondola does the work and then it's dumped.  If you felt like you need to try to drill, then you can drop off another unit on a cable, fill the sample bucket and recover or abandon the drill unit as necessary