For Questions That Don't Merit Their Own Thread

[StrandedonEarth]

 

2 hours ago, ARS said:

Wait, if it jump higher with only 1/6 gravity, should it fall slower than on earth? Meaning less force when crashing when compared if it jumps on earth?

No matter what planet or moon you jump on, you hit the ground with the same force you jumped off with.  Less only if you have air drag to slow you down

[ARS]

Ah I see

[kerbiloid]

11 hours ago, Racescort666 said:

Also, there would be no atmosphere for the engine to run on.

How could it be no atmosphere on the Moon when it has seas?!
Also if so what are the selenites breathing with?

P.S.
For sure, lubricants should quickly freeze and/or vaporize, so it would stop very soon.

[magnemoe]

5 hours ago, ARS said:

Wait, if it jump higher with only 1/6 gravity, should it fall slower than on earth? Meaning less force when crashing when compared if it jumps on earth?

No, if you jump up with an speed you will come down with the same speed, you just get more airtime and reach an higher attitude. 
More airtime increase chance that you come down bad, also driving fast toward a steep drop can easy give serious airtime and you also risk an bad landing, most who have driven fast rovers on mun or other low gravity places know about this
 

[kerbiloid]

Also any tank shot on the Moon is suborbital.
So, on the Moon you should attack from the direction of another opponent's site, maybe even in 500 km from the battlefield.
Then his missed anti-tank shots will be bombing his another facility.

P.S.
Are US (or somebody else's) tanks equipped with underwater driving equipment like Soviet ones?

Edited July 19, 2018 by kerbiloid

[monophonic]

31 minutes ago, kerbiloid said:

Are US (or somebody else's) tanks equipped with underwater driving equipment like Soviet ones?

Deep wading equipment is available for at least Abrams and Leopard 2 tanks. So yes. But the operation itself is not nearly as useful as it is often depicted. You don't normally have concrete entry and exit ramps and smooth solid bottom in rivers, like e.g. soviets liked to use in their demonstrations. Nor is the equipment itself armoured to any degree, so using it under fire is not a good idea. Therefore few armies practise with nor even acquire this equipment for their tanks.

[kerbiloid]

Spoiler

(So, "deep wading" - that's how it's called.)

No, I mean not this equipment usage itself, but that >1960s tanks are in fact ready pressurized space rovers which can run for several kilometers on the Moon or Mars without spacesuits.

Of course if attach an oxygen source.
Though, not very big one.
As a tank eats 3 kg of fuel/km, and the fuel is (CH2)n, so it requires 3 O / CH2 = 48/14 (* 3 kg/km)~= 10 kg of oxygen per kilometer.
Or ~20 kg of ammonium perchlorate / km.
A 500 kg pack of the perchlorate and a fumigator = 20 km tank raid.
Tanks and Mars. Created for each other.

Edited July 19, 2018 by kerbiloid

[p1t1o]

You can go one step further, if you bury a nuclear submarine on the Moon/Mars, it would make a perfect long term base. Make it a boomer and you have a ready made nuclear arsenal as well (and potentially a space-launch capability).

***

It should be noted that modern tanks are pressurised but do not contain large air supplies, rather they filter outside air.

It should also be noted that the Maus and other pre-50's/60's tanks are not pressurised and whilst may be capable of wading through water, may not be airtight in a near-vacuum.

 

[kerbiloid]

24 minutes ago, p1t1o said:

It should be noted that modern tanks are pressurised but do not contain large air supplies, rather they filter outside air.

You have a perchlorate pack on the tank back.
10 kg of oxygen per kilometer, while a crew of 3-4 requires just 3-4 kg/day.

24 minutes ago, p1t1o said:

It should also be noted that the Maus and other pre-50's/60's tanks are not pressurised and whilst may be capable of wading through water, may not be airtight in a near-vacuum.

Indeed, and I tried to show that Maus is not the best choice.

24 minutes ago, p1t1o said:

if you bury a nuclear submarine on the Moon/Mars, it would make a perfect long term base. Make it a boomer and you have a ready made nuclear arsenal as well

Yes and no.
1. Earth subs carry Earth missiles, with delta-V twice greater than Martian orbital speed. Unless you are going to be bombing another celestial body, it's a mass overspeed.
2. Submarines can withstand, say, 600 m depth, i.e. 60 atm, 6 MPa ~900 psi. SILO limit is up to 25000 psi.
So, there is no reason to bury submarines, better build a normal armored concrete SILO.

Edited July 19, 2018 by kerbiloid

[magnemoe]

2 hours ago, monophonic said:

 Deep wading equipment is available for at least Abrams and Leopard 2 tanks. So yes. But the operation itself is not nearly as useful as it is often depicted. You don't normally have concrete entry and exit ramps and smooth solid bottom in rivers, like e.g. soviets liked to use in their demonstrations. Nor is the equipment itself armoured to any degree, so using it under fire is not a good idea. Therefore few armies practise with nor even acquire this equipment for their tanks.

Unrelated to the moon however, it lacks both air and water.
And you could not run an standard electrical car on moon either simply because it require air cooling. 

Now one thing I learned in KSP is that if you want an fast rover, make is as light as possible this let it take way more punishment, you just has two high speed wheels in KSP, if you needed something heavy who could move fast of road an tank setup is pretty good, however something with 4 axes like the stryker might be better. 

[p1t1o]

42 minutes ago, kerbiloid said:

You have a perchlorate pack on the tank back.
10 kg of oxygen per kilometer, while a crew of 3-4 requires just 3-4 kg/day.

 

Indeed, and I tried to show that Maus is not the best choice.

I may have lost track of what kind of fantasy we are building...

Yes and no.
1. Earth subs carry Earth missiles, with delta-V twice greater than Martian orbital speed. Unless you are going to be bombing another celestial body, it's a mass overspeed.
2. Submarines can withstand, say, 600 m depth, i.e. 60 atm, 6 MPa ~900 psi. SILO limit is up to 25000 psi.
So, there is no reason to bury submarines, better build a normal armored concrete SILO.#

1. No problem, can do depressed trajectory, energy management manouvre or booster blowout to manage delta-V.

2. The missiles were an added bonus really, I was thinking more of self-contained/self-sufficient living space. Mostly want to bury it as it would look silly just sitting on the surface....it might tip over.

 

[kerbiloid]

39 minutes ago, p1t1o said:

1. No problem, can do depressed trajectory, energy management manouvre or booster blowout to manage delta-V.

You don't really need a depressed trajectory on Mars.
An SLBM booster is designed to release its delta-V as fast as possible, you can't manage it.
So, even if you don't ignite the third stage/PBV (like in Trident II or R-29RM) immediately after the booster (i.e. the two lower stages) have burnt out, your PBV already exceeds the Martian orbital speed (just ~3.5 km/s), and probably is getting to the Martian escape speed (~5 km/s).
As you don't have much air on Mars, but have to fly high to avoid terrain collisions, so air drag won't take out a lot of speed excess.

So, the Earth ICBM/SLBM are significantly overpowered on Mars. You should remove one stage or make them shorter.
But that in turn means that all lower half of your submarsine rocket compartment will be not used.

(On another hand, you can place your nukes on Martian orbit, as 3.5 km/s means spending much less fuel to rotate your plane of trajectory than on Earth,)

P.S.
Btw, BMD-1 is equipped with space seats Kazbek-D.
A Martian rover.
Chutes are included, but a heatshield should be added.
 

http://lemur59.ru/node/8963

Spoiler

 

Edited July 19, 2018 by kerbiloid

[p1t1o]

2 hours ago, kerbiloid said:

You don't really need a depressed trajectory on Mars.
An SLBM booster is designed to release its delta-V as fast as possible, you can't manage it.
So, even if you don't ignite the third stage/PBV (like in Trident II or R-29RM) immediately after the booster (i.e. the two lower stages) have burnt out, your PBV already exceeds the Martian orbital speed (just ~3.5 km/s), and probably is getting to the Martian escape speed (~5 km/s).
As you don't have much air on Mars, but have to fly high to avoid terrain collisions, so air drag won't take out a lot of speed excess.

So, the Earth ICBM/SLBM are significantly overpowered on Mars. You should remove one stage or make them shorter.
But that in turn means that all lower half of your submarsine rocket compartment will be not used.

(On another hand, you can place your nukes on Martian orbit, as 3.5 km/s means spending much less fuel to rotate your plane of trajectory than on Earth,)

P.S.
Btw, BMD-1 is equipped with space seats Kazbek-D.
A Martian rover.
Chutes are included, but a heatshield should be added.
 

http://lemur59.ru/node/8963

  Reveal hidden contents

 

Yes they are certainly overpowered, but you are slightly off about SLBMs. SLBMs are slightly dV-weak compared to your average ICBM, and are much better suited to depressed trajectory, they are not required to "release dV as fast as possible" - this would only result in making them less efficient. They fly through the same gravity well and atmosphere as larger rockets and thus their acceleration profile is similar.

In either case, a spiralling energy-management manouvre can turn a high-dV impulse into almost any trajectory you want. 

Unsuprisingly though, exact dV figures are very hard to come by for ICBMs/SLBMs.

Are we allowed to rebuild them in a differnt shape in this game? Because again it'd be better to build a bespoke Lunar/Martian weapon.

***

Question: how far could a nuke be thrown, on Mars or the Moon, with a Trebuchet?

 

EDIT: WAIT! Is that an ejection seat for a tank??

EDIT#2: Question #2: Using an Earth-Normal ICBM, a large one, could you hit the Moon from Mars? Or vice-versa? SPACEWAAAAAAAAAAR

Edited July 19, 2018 by p1t1o

[kerbiloid]

38 minutes ago, p1t1o said:

but you are slightly off about SLBMs. SLBMs are slightly dV-weak compared to your average ICBM

Trident II and R-29RM are ICBM (though maybe with reduced amount of reentry vehicles, but the same 11 000 km max).
Both of them have the 3rd stage combined with PBV, so you can choose either to spread warheads wider, or boost them farther.
(That's an SLBM feature, as unlike ICBM you never know will you launch them from 500 km or from 8000 km).

Their booster's 1st and 2nd stage in any case have the same, short, burn duration (about a minute for both) and is not presumed stop burning (though you can do this with some efforts).
So, when on Mars you get the first two stages exhausted, you find your PBV in orbit. While on Earth it would just achieve some minimal distance speed.

38 minutes ago, p1t1o said:

Are we allowed to rebuild them in a differnt shape in this game?

We can just have a single-stage booster made of original two stages, but it anyway will be shorter, and iirc idea was to use the Earth weapons on another body.
(Say, a rare old overmassed German tank which couldn't cross any bridge, as it was not on the Moon).

38 minutes ago, p1t1o said:

how far could a nuke be thrown, on Mars or the Moon, with a Trebuchet?

As its distance is very short, we can presume it's trajectory is parabolic.
And as its speed is low, probably we can omit the air drag.
So probably 6 times farther than on Earth, i.e. about a kilometer.

 pots of oil can't burn without air, so only with stones.

38 minutes ago, p1t1o said:

WAIT! Is that an ejection seat for a tank??

No, it just a shock absorption mechanism.
The same seat like on Soyuz and TKS VA, another modification. The upper end tilts up for 30 cm before the landing, then springs catch it on impact. And seat belts to fix the limbs and body.

38 minutes ago, p1t1o said:

Using an Earth-Normal ICBM, a large one, could you hit the Moon from Mars? Or vice-versa? SPACEWAAAAAAAAAAR

Afaik, R-36 family (aka Scarp/Satan) technically can deliver a single warhead from the Earth to Mars.
Its ballistic payload is 9 t, and its orbital warhead was 2.3 Mt (+ orbital block). When it's used as LV Dnepr, its orbital payload is 3.7 t.
So, probably a single not very big warhead technically can be delivered, though  should require something cubesat-like to activate it on reentry, as it doesn't have solar panels.

Edited July 19, 2018 by kerbiloid

[monophonic]

5 hours ago, kerbiloid said:

No, I mean not this equipment usage itself, but that >1960s tanks are in fact ready pressurized space rovers which can run for several kilometers on the Moon or Mars without spacesuits.

Unfortunately no. The deep wading kit includes a giant pressurised rubber ring to seal the turret ring against water leak. Other openings including the muzzle of the cannon are likewise sealed shut. These preparations make moving the turret or shooting the cannon impossible, which in itself is only a problem if you plan to engage in combat of course. The engine air intake and exhaust are directed to and from the surface through a snorkel. There is also a bilge pump to remove any water that still manages to leak in. Many a military has decided this is too much of a hassle and risk to bother, compared to e.g. building pontoon bridges.

So the tanks are not completely airtight. The NBC protection system works by pulling in air from the outside through a filter system. It pulls in enough to keep a small overpressure inside the vehicle, which ensures any leaks flow from inside to outside therefore keeping any toxic and/or radioactive materials outside the vehicle. In a vacuum you would be hard pressed to store enough air in the vehicle to last any useful lenght of time.

Now those submarines are a better bet on that front. For a few days at least, I suspect the vacuum and abrasive dust would do a number on the seals. Harder to get them moving without liquid water on the surface though.

16 minutes ago, kerbiloid said:

So, when on Mars you get the first two stages exhausted, you find your PBV in orbit.

Workaround is to program the missile so the PE of that orbit is underground and the trajectory crosses the surface downwards at the target point. It's just math, even if it's hard math.

[kerbiloid]

9 minutes ago, monophonic said:

Workaround is to program the missile so the PE of that orbit is underground and the trajectory crosses the surface downwards at the target point. It's just math, even if it's hard math.

There is even simpler workaround widely used in historical rockets: when you have boosted enough, direct your rocket into a "neutral direction", when further acceleration doesn't effect the distance, and let the fuel burn out.
But anyway this means on Mars you will spend a half of your fuel without a useful effect.

Mars radius = 3390 km, so a semi-circumference = 10600 km.
As Martian gravity is just 0.4 of normal, that means a cruise missile from Earth is nearly a global rocket on Mars.

17 minutes ago, monophonic said:

These preparations make moving the turret or shooting the cannon impossible, which in itself is only a problem if you plan to engage in combat of course.

Well, yes... Alas, tank is not enough good because of cannon.
An armored vehicle with external gun (like that 23mm on Almaz) is required.
Or something like this (a laser pack + a 12.7 machine-gun)

And a lot of epoxy to plug the cracks and keep the air inside.

Absolutely not enough for  500 km march, but to suddenly drop in 20 km from a competitors' base and capture it with an armored assault.

Ah, btw, T-14 Armata seems to have a crew capsule separated from the cannon, so maybe T-14 can be a space tank.

[p1t1o]

1 hour ago, kerbiloid said:

Their booster's 1st and 2nd stage in any case have the same, short, burn duration (about a minute for both) and is not presumed stop burning (though you can do this with some efforts).
So, when on Mars you get the first two stages exhausted, you find your PBV in orbit. While on Earth it would just achieve some minimal distance speed.

3rd time lucky maybe : ENERGY MANAGEMENT MANOUVRE

Basically it drives around the block a few times before leaving

Thus a high-dV booster can be made to act like a lower dV one.

[kerbiloid]

6 minutes ago, p1t1o said:

ENERGY MANAGEMENT MANOUVRE

It's an anti-aircraft missile, it came from another tale.

ICBM/SLBM doesn't need to hit something fast and close in seconds after the launch, its T/W is much lower.

It just must cowardly get away before her colleague gets here.

(Also not sure if such manouvre is relevant in near-vacuum when fins don't work.)

Edited July 19, 2018 by kerbiloid

[p1t1o]

14 hours ago, kerbiloid said:

It's an anti-aircraft missile, it came from another tale.

Specifically an ABM, which has a wide engagement envelope, not for close-in engagement but for high-altitude anywhere from directly above to one or two hundred mile cross-range, so there's a lot of dV in it that may or may not be used.

ICBM/SLBM doesn't need to hit something fast and close in seconds after the launch, its T/W is much lower.

Sigh, well, they are capable of it, exactly for the reason discussed.

https://fas.org/nuke/guide/usa/slbm/c-4.htm

"Missile range is controlled by trajectory shaping with Generalized Energy Management Steering [GEMS)"

It just must cowardly get away before her colleague gets here.

(Also not sure if such manouvre is relevant in near-vacuum when fins don't work.)

Thrust Vectoring.

 

Edited July 20, 2018 by p1t1o

[monophonic]

15 hours ago, kerbiloid said:

Ah, btw, T-14 Armata seems to have a crew capsule separated from the cannon, so maybe T-14 can be a space tank.

Yes, Armata would be a better starting point. You wont even do extra work vacuum proofing the power train, since you have to fix that first anyway.  Some newer IFVs feature unmanned turrets too, if you need more space and/or don't need that extreme armor protection or big gun an MBT has.

Of course ground drones are a thing and there are armed ones too. So, maybe you can just do away with the meatbags and their cumbersome needs entirely.

[p1t1o]

Frankly Imma just stay up in space in whatever I arrived in, dropping rocks.

[kerbiloid]

1 hour ago, monophonic said:

Of course ground drones are a thing and there are armed ones too. So, maybe you can just do away with the meatbags and their cumbersome needs entirely.

The problem is: if we are undertaking a ground attack instead of just nuking the Martian base, we are probably going to capture it, not just destroy.
And thus we need humans.

So, probably a temporary Martian compromise would be orbital/suborbital dropping of a squad of unpressurized BMD-1 with troopers inside (that's by design) in 20..30 km from the Martian base.
Troops should be wearing lightweight rescue suits (that's enough for their in any case short assault).
BMD 1x73+3x7.62 probably would be OK in Martian atmosphere (like that 23mm on Almaz).
Anti-tank missile will fail, as it's stabilized with rotation. So, fins won't work, the missile is useless.

After reaching the aim close proximity, troops will get out and capture the Martian base.

When some kind of Armata or drones will be available, this will be an additional support.

1 hour ago, p1t1o said:

"Missile range is controlled by trajectory shaping with Generalized Energy Management Steering [GEMS)

In any case. But this doesn't mean a missile should be flying in weird trajectories to burn out excessive fuel.
C-4 have been replaced with D-5 long ago, haven't they? So, you would use D-5 on Mars, and it's much more overpowered for its gravity.

1 hour ago, p1t1o said:

Thrust Vectoring

It doesn't matter how, it matters - why?

Edited July 20, 2018 by kerbiloid

[p1t1o]

52 minutes ago, kerbiloid said:

In any case. But this doesn't mean a missile should be flying in weird trajectories to burn out excessive fuel.
C-4 have been replaced with D-5 long ago, haven't they? So, you would use D-5 on Mars, and it's much more overpowered for its gravity.

It doesn't matter how, it matters - why?

[monophonic]

3 hours ago, kerbiloid said:

In any case. But this doesn't mean a missile should be flying in weird trajectories to burn out excessive fuel.
C-4 have been replaced with D-5 long ago, haven't they? So, you would use D-5 on Mars, and it's much more overpowered for its gravity.

"Flying in weird trajectories to burn out excessive fuel" is exactly what GEMS is. You would use a D-5 (or Bulava) on Mars for exactly the same reason you would use a BDM-1 or Armata in place of a bespoke Mars optimized fighting vehicle.

[kerbiloid]

54 minutes ago, monophonic said:

You would use a D-5 (or Bulava) on Mars for exactly the same reason you would use a BDM-1 or Armata in place of a bespoke Mars optimized fighting vehicle.

No, I would use a cruise ballistic missile with 2000...5000 km, which on Mars gets intercontinental if not global.
Something Pershing-sized, or an early single-stage SLBM like R-27 or Polaris.
But they don't fit the existing submarines, and a submarine hull is less strong than a SILO.

I defintely wouldn't spend twice more energy than required.

Edited July 20, 2018 by kerbiloid