For Questions That Don't Merit Their Own Thread

[K^2]

3 hours ago, magnemoe said:

None for long term high g trust and pointless to even think about before somebody make an touchship. 

Even then, it's hard for me to imagine scenario where you'd need acceleration greater than 1g desperately enough to sacrifice mobility around the ship for the duration. A 1g torch gets you to Neptune in just over two weeks. At 100g, it'd still be almost a day. Two weeks on a cruise ship or a day in a vat of fluid? I don't think I'd opt for later, unless this is a time-critical mission. And on more common inner system routes, high acceleration would make even less sense.

Likewise, if we go interstellar, relativity kicks in. A quirk in how proper acceleration works at relativistic speeds means that both the Earth time and ship time aren't impacted all that greatly by acceleration. A 1g tocrch is perfectly capable of running to the center of the galaxy and back within lifetime of the crew. Increasing acceleration by factors of 10 buys you back a few years from that. Exponential increases in acceleration give you linear improvements. Even by the time you get to 1000g, it doesn't make a huge difference. And in terms of time in Earth frame it doesn't make a difference at all. The round trip will be 50k years of Earth time no matter what.

So I don't think sustained high g is practical unless we can make it work like in sci-fi, where you still get a comfortable deck to walk around the ship.

[Space Nerd]

21 hours ago, JoeSchmuckatelli said:

Info on 18 Sco? 

 

I remember reading years ago that this is one of the closet Sol analog stars - getting even Margaret Turnbull excited - but I can't find much more about it. 

There was an article about its metalicity and speculation that it is too dusty for it to likely have a rocky planet in the habitable zone... But then I remember talk about excitement to see what the Webb spotted (back when it was on schedule)...

 

So I'm surprised I don't see much about it - but wouldn't it be one of the most studied stars in the recent years?  Shouldn't there be rich information from Kepler and TESS studies that are published/available to the average Joe?

 

All I see is 'no planets have been discovered' - but I haven't seen why 

I'll just drop this here, hope that's enough.

https://en.m.wikipedia.org/wiki/18_Scorpii

18 Sco isn't in the field of view of Kepler original mission, and I don't know if it's observed by K2 or TESS.

Anyway, my question :

I'm making some space themed art featuring proxima b and trappist-1 e, and I drew purple and red plants on them for aesthetics (black doesn't look that good), is that scientifically plausible?

[p1t1o]

FunFact^TM: In the movie "The Abyss" they feature liquid breathing for deep diving and they immerse a rat in the liquid and remove it again. They used actually real perfluorocarbon, which the rat really did breathe and really did survive.

 

On 4/29/2020 at 5:05 AM, kerbiloid said:

The only thing confusing me in the sci-fi anti-g liquid beds is that the internal organs keep pressing the back from inside with same force.

Thats just so that the pressure is equal over the whole contact area, it doesnt increase G-tolerance, only reduces bruising. Which i suppose does increase tolerance in a way. Especially if you have to endure repeated periods of high-G.

Edited May 1, 2020 by p1t1o

[kerbiloid]

15 minutes ago, p1t1o said:

FunFact^TM: In the movie "The Abyss" they feature liquid breathing for deep diving and they immerse a rat in the liquid and remove it again. They used actually real perfluorocarbon, which the rat really did breathe and really did survive.

Yes, but it was for omnidirectional counter-pressure, not against acceleration along one axis when kidneys are pressed into the ribs, eyeballs into the sockets, and vertebrae are trying to slide on each other.
Also blood vessels are not clamped with the neighboring tissues.

So, maybe I'm wrong, but that looks like different conditions.

This makes me guess that this way can be effective just for enough low overloads, againt lungs collapse or so, not against mechanical damages and vessel clamping.

I mean, not any pressure is hydrostatic.

Edited May 1, 2020 by kerbiloid

[Spacescifi]

Most of softer science scifi varieties have this:

Glowing engine ports with no apparent rocket nozzle at all, leading me to wonder if there is, or ever will be a legit reason to embed the nozzle into the ship's hull?

Like I know why we do not IRL.

1. Saves room on disposable staged boosters.

2. Dumps nozzle heat into the air during launch, otherwise the ship itself absorbs that heat, which unless it can be converted to do any work really does the ship no favors.

Any legit reason why one would do embedded nozzles besides doing it because scifi does it?

Possible reason? If you have a heat rejection or absorbtion system system much better than the dumping radiant energy or conducting it to the air, then I suppose it would make plenty of sense.

What would be definitely fiction for our current abilities is any unibtanium that could actually provide that capabilty.

Which would probably make most thermal damage the toughest resistance buff such a ship would have.

Just layer the hull with unobtanium.

[kerbiloid]

Easy access for maintenance without EVA.

[DDE]

Broke:

6 hours ago, Spacescifi said:

 

Woke:

[wumpus]

4 hours ago, DDE said:

Broke:

Woke:

 

Not to mention all the issues trying to create a counter moment to deal with the issue that your thrust/direction/center of mass aren't all in one line.  NCC1701 was even worse, although a bigger problem was how flimsy the main structure was. 

[Nightside]

12 hours ago, Spacescifi said:

Most of softer science scifi varieties have this:

Glowing engine ports with no apparent rocket nozzle at all, leading me to wonder if there is, or ever will be a legit reason to embed the nozzle into the ship's hull?

Like I know why we do not IRL.

1. Saves room on disposable staged boosters.

2. Dumps nozzle heat into the air during launch, otherwise the ship itself absorbs that heat, which unless it can be converted to do any work really does the ship no favors.

Any legit reason why one would do embedded nozzles besides doing it because scifi does it?

Possible reason? If you have a heat rejection or absorbtion system system much better than the dumping radiant energy or conducting it to the air, then I suppose it would make plenty of sense.

What would be definitely fiction for our current abilities is any unibtanium that could actually provide that capabilty.

Which would probably make most thermal damage the toughest resistance buff such a ship would have.

Just layer the hull with unobtanium.

Those are just turn signals and brake lights mandated by the over regulated feds. 

[Shpaget]

16 hours ago, Spacescifi said:

leading me to wonder if there is, or ever will be a legit reason to embed the nozzle into the ship's hull?

Like I know why we do not IRL.

We actually do embed them.

 

[Flying dutchman]

North/south america splits at the border between Panama and Colombia, if i launch a firework (small gunpowder rocket) over the border....

 

 

I will have launched am icbm?

[kerbiloid]

By definition an ICBM should have min range 3 000 nm / 5 500 km.

[p1t1o]

On 5/1/2020 at 4:36 PM, kerbiloid said:

Yes, but it was for omnidirectional counter-pressure, not against acceleration along one axis when kidneys are pressed into the ribs, eyeballs into the sockets, and vertebrae are trying to slide on each other.
Also blood vessels are not clamped with the neighboring tissues.

So, maybe I'm wrong, but that looks like different conditions.

This makes me guess that this way can be effective just for enough low overloads, againt lungs collapse or so, not against mechanical damages and vessel clamping.

I mean, not any pressure is hydrostatic.

No I know all that, it was just for interest and to show that the fluid does actually work and has been tested on live animals. Pretty good proof of concept even if the specific fluid is not suitable for high-G applications.

***

It does make me think though - when exactly would humans want to be subjected to high-G in space?

Not for travel, as you can get anywhere realistic in quick-smart time using a fraction of a G. You can get to other stars in a fraction of a human lifespan with only 1G. Heck, with a torch drive, you can travel to the other side of the universe in less than 1 subjective century, with only 1G.

For combat? Well you will be beaten by unmanned craft accelerating at 400G every single time (we had missiles on the books with this capability in the 1960's, it is fully plausible that more complex craft could replicate or improve on this), not least because they wont be carrying a cubic metre of extra fluid mass (mostly because there are limits to the Gforce a human can withstand even with fluid support). Space fighters (a-la XWings and Starfuries) are an obsolete idea.

 

 

***

On 5/3/2020 at 3:43 AM, Spacescifi said:

Most of softer science scifi varieties have this:

<snip>

FunFact^TM: According to the Star Trek: The Next Generation Technical Manual, impulse engines are fully fledged, open-core fusion rockets. I was always disappointed that when they "went to one quarter impulse" that it was just a warm glow and not an actinic spear of blinding light.

Also, you can put the nozzle where you want because A) structural integrity field makes the entire ship infinitely rigid and B) the warp drive works by manipulating the mass of the ship, meaning that altering the centre of mass is trivial for them. (Meaning: we design it how we like, then make the magic work around it)

 

Long story short - star trek is not science fiction. It is what is called a "space opera" since it is essentially normal stories just set in space, none of the plots actually require it to be set in the future flying around in spaceships. Ok probably a few do, but it has never pretended to be realistic, it doesnt need to be.

[magnemoe]

On 5/3/2020 at 11:11 AM, DDE said:

Broke:

Woke:

The ports on an star trek ship is not an engine but an funnel or exhaust pipe to get rid of engine waste, typical helium if you use fusion. 
Same with the bells at the back of the star destroyers but Seeing them now I will always think of the bottom of Starship with the three vacuum and three surface engines. See if you can un-see it now  Tell Musk and the military version of Starship will get 4 surface engines.
Yes they went with the design because it looks cool, here the ports are not in flush but nozzles too but they have an skirt. 

[kerbiloid]

1 hour ago, p1t1o said:

when exactly would humans want to be subjected to high-G in space?

1. A high-speed escape pod.
Say, you're working in an antimatter storage and suddenly touch the wall and feel that it's nicely warm.
So, you have a minute to take the seat and inhale the liquid and a minute to get 1000 km away.

2. An escape pod of a high-speed interplanetary ship.
Say, it's equipped with a magnetic heatshield, so on aerobraking the heat is not a problem.
But the braking path is still 1000 km, while yur speed is 50 km/s. So, you should survive 100 g overloads.

3. p.2. The same but for the escape pod of a Martian base.
A shot from Mars, an aerobraking into Earth.

4. An escape pod of an orbital missile base.
You launch missiles, jump into the escape pod and two mintes later (when the base is inevitably hit by an antisat missile) you are already far away.

5. A cargo mass driver as an emergency option to evacuate the crew.

6. An orbital rotavator, catching a crewed capsule at 30..40 g overloads at the lowest point.

7. An escape pod of an interplanetary ship which is going to lithobrake, to eject back.

8. An anti-seismic vault to survive under GZ.

9. Extreme tourism. Fly through the Saturn rings and touch the clouds.

10. Some hi-tech drive which can't produce low TWR (say, it's not a rocket, so you can just increase the ship mass to decrease the acceleration).

11. Sun & Oberth maneuver.

12. Landing on the side surface of a rotating orbital station (in case if you can't match the speed, say it's chaotically dangling).

13. Dropships. Pass through the anti-aicraft defense quickly (see Heinlein).

14. Space pirate. Orbital boarding.

15. Emergency drop of heavy cargo with same thrust. So survive the ship jump.

16. Surviving in a 100 g centrifuge.

17. Surviving next to a potential explosion which throws the capsule away.

Edited May 4, 2020 by kerbiloid

[Flying dutchman]

5 hours ago, kerbiloid said:

By definition an ICBM should have min range 3 000 nm / 5 500 km.

so i did not launch an intercontinal ballistic missile but i launched a balistic missile intercontinentally?

[K^2]

5 hours ago, p1t1o said:

It does make me think though - when exactly would humans want to be subjected to high-G in space?

Unlike sustained high-G, the uses for spikes in high accelerations are going to be useful for absolutely everything. Without a limit, it even makes lithobraking a viable landing option. It's much easier to summarize when you don't need high-G, and that's pretty much covered by, "When it's sustained."

[Nightside]

2 hours ago, Flying dutchman said:

so i did not launch an intercontinal ballistic missile but i launched a balistic missile intercontinentally?

If that is your case, it sounds like you should still hire a lawyer. 

[Shpaget]

10 hours ago, Flying dutchman said:

so i did not launch an intercontinal ballistic missile but i launched a balistic missile intercontinentally?

You're still one semantic short of alphabet people on your doorstep.

A missile is almost universally implied to be guided. You need to up your fireworks game.

[p1t1o]

18 hours ago, K^2 said:

Unlike sustained high-G, the uses for spikes in high accelerations are going to be useful for absolutely everything. 

Such as? Still cant accelerate hard enough to dodge an unmanned weapon, dont need high G at all for orbital manouvres or travel...?

And to add, fluid support or not, spikes are a lot harder to endure than sustained, slower-onset forces, whether it be acceleration or pressure. Lithobraking at least, certainly seems too far of a reach to me. I cant think of how a 10,000G-induced pressure spike would harm you, but I bet it wouldnt be healthy. And the ship would have to be built like a tank to stop the cabin from rupturing and the crew being ejected with extreme force through the gaps in the hull.

Even space marine drop pods have retro rockets

 

 

[wumpus]

2 hours ago, p1t1o said:

Such as? Still cant accelerate hard enough to dodge an unmanned weapon, dont need high G at all for orbital manouvres or travel...?

And to add, fluid support or not, spikes are a lot harder to endure than sustained, slower-onset forces, whether it be acceleration or pressure. Lithobraking at least, certainly seems too far of a reach to me. I cant think of how a 10,000G-induced pressure spike would harm you, but I bet it wouldnt be healthy. And the ship would have to be built like a tank to stop the cabin from rupturing and the crew being ejected with extreme force through the gaps in the hull.

Even space marine drop pods have retro rockets

 

 

I'd assume collisions.  Like air-bags, only capable of surviving much higher velocity collisions.

You know Jeb will be trying lithobraking the minute he has his mits on something like this...

[K^2]

5 hours ago, p1t1o said:

Such as? Still cant accelerate hard enough to dodge an unmanned weapon, dont need high G at all for orbital manouvres or travel...?

And to add, fluid support or not, spikes are a lot harder to endure than sustained, slower-onset forces, whether it be acceleration or pressure.

Every single orbital maneuver is more efficient if you perform it in less time. Landing and takeoff from airless body are prime examples, as their efficiency is directly governed by available TWR. It also opens up a lot of options in reentry. If your crew can survive a belly-fop against atmo, you don't need much of a heat shield, and the amount of time spent in reentry, where craft is particularly detectable, vulnerable, and often cut off from communications, is greatly reduced. But you shouldn't underestimate dodging a missile, either. Unless the kill vehicle heading for you is surrounded by thrusters, its ability to accelerate in transverse direction might be quite limited, allowing you to dodge. You also shouldn't underestimate the benefits of abandoning ship if you can't dodge. Being able to eject at really high accelerations in just a fraction of a second can make a difference between losing the ship and losing the ship with all hands.

We're also not limited to submerging crew in fluids when we're talking about short spikes. By far the largest difference in densities, once you fill cavities, is between tissues and bones. If you don't mind additional supports surgically added to your skeleton that get attached to the ship, you can significantly increase the high-g tolerance, possibly well into hundreds of gravities. It'd break every bone in your body and skewer your flesh with shards of bone if you tried to move during a maneuver, so it's definitely not good for sustained, but might be just what you need for some of the maneuvers discussed above.

We can also add mag fields to provide fairly uniform force across your body via diamagnetic levitation effect. What we can apply continuously will only give you a few Gs, and you couldn't move much because the field can only be made uniform for particular body configuration, but we have ways of generating spikes of magnetic fields that are much stronger, possibly giving you tens of Earth gravities with minimal setup. If you're prepared to make some surgical modifications, this can be greatly extended. Possibly also pushed into high double digits or low triple digits. Combining the two approaches above can push you into territories where structural integrity of the ship and equipment is starting to become as much of a problem.

Finally, gravitomagnetics is not quite as sci-fi as it might sound once we get to sufficient scale. Brief spike of artificial gravity induced by a sudden change in gravitomagnetic flux, such as discharge of a capacitor in external magnetic field, can provide high force uniformly across every atom of crew and compartment with minimal tidal distortions. Now the key word here is brief, and the system needed to generate this will be rather large, as are energies involved. So I can't imagine this being useful for absolutely anything but an emergency escape, but that is a plausible way to generate accelerations that go way beyond ability of even structural materials of withstanding the stress.

[magnemoe]

3 hours ago, K^2 said:

Every single orbital maneuver is more efficient if you perform it in less time. Landing and takeoff from airless body are prime examples, as their efficiency is directly governed by available TWR. It also opens up a lot of options in reentry. If your crew can survive a belly-fop against atmo, you don't need much of a heat shield, and the amount of time spent in reentry, where craft is particularly detectable, vulnerable, and often cut off from communications, is greatly reduced. But you shouldn't underestimate dodging a missile, either. Unless the kill vehicle heading for you is surrounded by thrusters, its ability to accelerate in transverse direction might be quite limited, allowing you to dodge. You also shouldn't underestimate the benefits of abandoning ship if you can't dodge. Being able to eject at really high accelerations in just a fraction of a second can make a difference between losing the ship and losing the ship with all hands.

We're also not limited to submerging crew in fluids when we're talking about short spikes. By far the largest difference in densities, once you fill cavities, is between tissues and bones. If you don't mind additional supports surgically added to your skeleton that get attached to the ship, you can significantly increase the high-g tolerance, possibly well into hundreds of gravities. It'd break every bone in your body and skewer your flesh with shards of bone if you tried to move during a maneuver, so it's definitely not good for sustained, but might be just what you need for some of the maneuvers discussed above.

We can also add mag fields to provide fairly uniform force across your body via diamagnetic levitation effect. What we can apply continuously will only give you a few Gs, and you couldn't move much because the field can only be made uniform for particular body configuration, but we have ways of generating spikes of magnetic fields that are much stronger, possibly giving you tens of Earth gravities with minimal setup. If you're prepared to make some surgical modifications, this can be greatly extended. Possibly also pushed into high double digits or low triple digits. Combining the two approaches above can push you into territories where structural integrity of the ship and equipment is starting to become as much of a problem.

Finally, gravitomagnetics is not quite as sci-fi as it might sound once we get to sufficient scale. Brief spike of artificial gravity induced by a sudden change in gravitomagnetic flux, such as discharge of a capacitor in external magnetic field, can provide high force uniformly across every atom of crew and compartment with minimal tidal distortions. Now the key word here is brief, and the system needed to generate this will be rather large, as are energies involved. So I can't imagine this being useful for absolutely anything but an emergency escape, but that is a plausible way to generate accelerations that go way beyond ability of even structural materials of withstanding the stress.

This is true, however orbital mechanic kind of break with  fusion or similar technology who is required for this in the first place. 0.1 g with 100.000 s is better than 1 g at 10.000 s ISP. 
Exception is stuff like getting out of radiation fields and random walk in combat. 

[ARS]

Is there any reason why submarines almost always colored black? (Or at least the portion that'll be visible when it surfaces since the bottom portion that's underwater will also almost always red) If there's no particular reason, especially that impacts it's combat performance or stealth (as long as it stays underwater), does it mean it's fine to paint the submarine with dazzle camo or for the extreme, garish color like pink?

[magnemoe]

2 hours ago, ARS said:

Is there any reason why submarines almost always colored black? (Or at least the portion that'll be visible when it surfaces since the bottom portion that's underwater will also almost always red) If there's no particular reason, especially that impacts it's combat performance or stealth (as long as it stays underwater), does it mean it's fine to paint the submarine with dazzle camo or for the extreme, garish color like pink?

Good question, think WW 2 ones was gray like most warships but they spent most of their time on the surface anyway. 
my guess is to be less visible from the air then close to the surface.