How ICBM Calculate its trajectory?

[p1t1o]

11 minutes ago, DerekL1963 said:

Nope, the AIRS reference sphere was developed for MX (which was later named Peacekeeper), and has now been installed on Minuteman-III.   Poseidon uses a more conventional gimbal based system.

arg, I thought peacekeep and poseidon were essentially the same, doh!

[hugix]

I cannot believe this hasn't been posted

 

 

[Thomas, a Kerbonaut]

On 1/11/2018 at 8:37 AM, GoSlash27 said:

Interesting video The bus is liquid fueled, and fine- tunes the trajectory to the desired impact point.

Usually ICBMs are stored for a long time, and should be launched as quickly as possible after the comand. It might be some kind if cold gas powered RCS. 

[p1t1o]

3 hours ago, Thomas, a Kerbonaut said:

Usually ICBMs are stored for a long time, and should be launched as quickly as possible after the comand. It might be some kind if cold gas powered RCS. 

Looking at the "Chevaline" bus, it appears to have a hydrazine-fuelled RCS:

"The red tank is labled "Hydrazine Tank" and the things under it are labled "Thermal Batteries."

 

[Cheif Operations Director]

This only applies to ICBMs not SLBMs and Cruise Missiles

Most likely their targeting system is less sophisticated that thought. I mean if you launch a rocket in KSP in KSP and keep it on a track just to space and then cut the engine you can easily target an area. I've gotten bored before and KSP and launched ICBMs and hit very close to KSC. The Guidance system would most likely by an altimeter along with gyroscope to create a computerised 3D map of its surroundings and then just keep itself on course. Then at the end during MIRV separation most likely a small "RCS" system align each ICBM with its target. 

 

My understanding is that MIRVs target a general area with separate warheads and not a radical distance. For example if the US Launched a minuteman with 3 Warheads at Russia 3 Warheads would hit Moscow in 3 areas around moscow in a triangle formation most likely it's not like 1 Warhead is going for red square 1 for st Petersburg and 1 for Vladivostok that when taking into account orbital mechanics is obsurd.

In conclusion

Im sure the new missiles such are sophistaced but the legacy missiles such as Minuteman are most likely pretty basic.

Note: These are just my thoughts I honestly do not know for sure. 

When we talk about guidance systems it is important to note SLBMs and especially cruise missiles are entirely differant. I know cruise missile use a radar "signature/ ID" system but ICBMs move to fast for it. The SLAM program was the first to use it but it was more of a nuclear armed intercontinental cruise missile (unofficial name) than an ICBM. 

They have tried star navigation too and it failed.

My statements do not apply to precision strike ICBMs

[magnemoe]

1 hour ago, Cheif Operations Director said:

This only applies to ICBMs not SLBMs and Cruise Missiles

Most likely their targeting system is less sophisticated that thought. I mean if you launch a rocket in KSP in KSP and keep it on a track just to space and then cut the engine you can easily target an area. I've gotten bored before and KSP and launched ICBMs and hit very close to KSC. The Guidance system would most likely by an altimeter along with gyroscope to create a computerised 3D map of its surroundings and then just keep itself on course. Then at the end during MIRV separation most likely a small "RCS" system align each ICBM with its target. 

 

My understanding is that MIRVs target a general area with separate warheads and not a radical distance. For example if the US Launched a minuteman with 3 Warheads at Russia 3 Warheads would hit Moscow in 3 areas around moscow in a triangle formation most likely it's not like 1 Warhead is going for red square 1 for st Petersburg and 1 for Vladivostok that when taking into account orbital mechanics is obsurd.

In conclusion

Im sure the new missiles such are sophistaced but the legacy missiles such as Minuteman are most likely pretty basic.

Note: These are just my thoughts I honestly do not know for sure. 

When we talk about guidance systems it is important to note SLBMs and especially cruise missiles are entirely differant. I know cruise missile use a radar "signature/ ID" system but ICBMs move to fast for it. The SLAM program was the first to use it but it was more of a nuclear armed intercontinental cruise missile (unofficial name) than an ICBM. 

They have tried star navigation too and it failed.

My statements do not apply to precision strike ICBMs

You use inertial navigation systems, they have been around for a long time, yes you program the missile for an trajectory but missile uses the navigation system to keep that, the warhead bus compensates for errors and release warhead, it can then change trajectory and drop others, as you say you can not do very large trajectory changes so its limits but I think you can still hit targets many kilometers apart, some earlier missiles did not have that capability so multiple warheads was mostly to hit an large area. 

inertial navigation works well for ICBM since they only uses an few minutes before they are in space. On an cruise missile who can fly for hours the inaccuracy will grow to high to be practical. 

[kerbiloid]

SLBM needs astrocorrection because they don't know their coordinates (historically, let's remember when they were created). In case if radiocorrection is unavailable.
ICBM doesn't need it because it always knows.

Both have inertial (main) and radiocorrection (to adjust it precisely after ascending).

Since MX had a super-duper but a supercomplicated inertial one, it presumably doesn't need additional radiocorrection.

Edited July 20, 2018 by kerbiloid

[Cheif Operations Director]

2 hours ago, kerbiloid said:

SLBM needs astrocorrection because they don't know their coordinates (historically, let's remember when they were created). In case if radiocorrection is unavailable.
ICBM doesn't need it because it always knows.

Both have inertial (main) and radiocorrection (to adjust it precisely after ascending).

Since MX had a super-duper but a supercomplicated inertial one, it presumably doesn't need additional radiocorrection.

 

2 hours ago, magnemoe said:

You use inertial navigation systems, they have been around for a long time, yes you program the missile for an trajectory but missile uses the navigation system to keep that, the warhead bus compensates for errors and release warhead, it can then change trajectory and drop others, as you say you can not do very large trajectory changes so its limits but I think you can still hit targets many kilometers apart, some earlier missiles did not have that capability so multiple warheads was mostly to hit an large area. 

inertial navigation works well for ICBM since they only uses an few minutes before they are in space. On an cruise missile who can fly for hours the inaccuracy will grow to high to be practical. 

MX Peacemaker is a very recent ICBM. All I'm saying is that I'm sure precision strike ICBMs do have more complicated targets system but they we intentionally not developed because of concerns about the Balance of power.. We could have make them hit a pin on the ground we did not for a reason (the reasons to dumb I know) If you look at a Titan II (not the Gemini version) I do not think it would be that complicated. 

[p1t1o]

32 minutes ago, Cheif Operations Director said:

MX Peacemaker is a very recent ICBM. All I'm saying is that I'm sure precision strike ICBMs do have more complicated targets system but they we intentionally not developed because of concerns about the Balance of power.. We could have make them hit a pin on the ground we did not for a reason (the reasons to dumb I know) If you look at a Titan II (not the Gemini version) I do not think it would be that complicated. 

Hmm. This doesnt quite tally with history. Although it IS correct that many pieces of weapons technology were discarded, supressed or ifnored precisely to avoid escalation in the arms race, or increased political tension between East and West (the most obvious being project Pluto). But I have not heard - though that does not mean it didnt happen - of accuracy systems being treated this way.

Precise weapons were a *stabilising* factor, as it enabled militaries to target actual installations rather than dropping a 15megaton city killer in the exact region.

Though it was also de-stabilising in that if you can precisley targhet only military targets, you might be less discouraged from starting a war. This is balanced by the enemy also increasing accuracy, disinclining you from the same thing. All in all, I think the drift away from targeting regions with apocalyptically-sized weapons had the more calming effect.

They were also strategically very important as accurate systems do not require such large warheads, meaning that your strategic reserves of fissile materials can make more weapons, and are much cheaper.

The drive from the beginning of the cold war to its end was always more accurate weapons with a longer range.

It certainly would not help stability to de-accuratise your Titan only to put a monstrous city-killer warhead on top.

A large factor in the accuracy of ICBMs is the mapping of the gravitational potential of the Earth (that is, precisely mapping the strength of the gravity field and how it changes, it is not smooth), which could not happen until satellites were A) possible and B) much cheaper. This allows inertial systems to be much more accurate (as an inertial table cannot detect changes in acceleration due to changes in gravity).

There are no political action required to explain the innaccuracy of older-generation missiles.

The system used in the MX missile was a step change in the accuracy of inertial navigation, and for ICBMs was/is regarded as the pinnacle of inertial navigation, as a more accurate system would not increase the acuracy of the missile as other error sources were now dominant.

 

I would be very interested to know if you happen to have any information backing up the idea that more accurate systems were available but not used.

 

Pictured: a gravitational potential map of the Earth

 

4 hours ago, Cheif Operations Director said:

Most likely their targeting system is less sophisticated that thought. I mean if you launch a rocket in KSP in KSP and keep it on a track just to space and then cut the engine you can easily target an area. I've gotten bored before and KSP and launched ICBMs and hit very close to KSC.

Do not underestimate how much more complex the real world is than a simulation. For one thing, Kerbin is 10x smaller than Earth, that does not mean the error would be 10x larger, it will be significantly more than that because the missile flies MUCH further than 10x the distance. And related to the above map, the gravity field of kerbin is perfectly spherical. And many more factors beside such as wind, hypersonic aerodynamics (which are not simulated at all in KSP), etc. We also have perfect access to perfect sensor data in KSP, in reality you actually have to make measurements - which will have their own error bands - and extrapolate from that. In KSP you know your position, attitude and speed to what? 8 or 9 significant figures? This is not so in reality. Although now we have GPS, which helps a lot, military systems are always designed assuming this would not be available in time of war.

It is MUCH easier to do in KSP than real life.

Edited July 20, 2018 by p1t1o

[Cheif Operations Director]

MIRVs allow for this not targeting systems

[p1t1o]

Just now, Cheif Operations Director said:

MIRVs allow for this not targeting systems

MIRVs allow for what?

[Cheif Operations Director]

1 minute ago, p1t1o said:

MIRVs allow for what?

Targeting military installations, once a warhead begins re-entry their is no course correction. This means it's all in the RCS system and better trajectories. 

1 minute ago, p1t1o said:

MIRVs allow for what?

Targeting military installations, once a warhead begins re-entry their is no course correction. This means it's all in the RCS system and better trajectories. 

[p1t1o]

4 minutes ago, Cheif Operations Director said:

Targeting military installations, once a warhead begins re-entry their is no course correction. This means it's all in the RCS system and better trajectories. 

1. MIRV =/= MRV

2. ICBMs are more accurate than you think.

3. Getting an ICBM to be that accurate is more difficult than you think.

4. There is a type of reentry vehicle called aMARV, which entered public knowledge several decades ago. You will find next to nothing about it on the internet, care to guess why? It is *extremely* manouverable in the descent. There is sufficient science in the public domain to be fairly sure that this technology exists, works, and is highly classified. Whether or not it is actually deployed is anyones guess, but its a real thing - manouverable RVs are very possible.

Here is a picture of aMARV executing a pull-up manouvre during reentry:

[Cheif Operations Director]

Ok most mirvs are not 

[kerbiloid]

1 hour ago, Cheif Operations Director said:

MX Peacemaker is a very recent ICBM.

I was in school when it was recent. And this was long ago.

1 hour ago, Cheif Operations Director said:

If you look at a Titan II (not the Gemini version) I do not think it would be that complicated. 

Titan II had 9 Mt yield.
It doesn't care about +/- 2 km. It needs neither radio, no astro. It's perfect itself.

50 minutes ago, p1t1o said:

It certainly would not help stability to de-accuratise your Titan only to put a monstrous city-killer warhead on top.

Titan could be used as a counter-force against weak open pads of R-7 and other such things, and against some later SILOs which were being placed in close groups*, and which were having a weak command post.
But this was in late 60s.

*For reason. If you are trying to hit a close group with several warheads, the first exploded will kill all her sister warheads in air, but just one SILO. At least, that was the idea.

Spoiler

50 minutes ago, p1t1o said:

 

Hey! I can see bumps in our back street!

37 minutes ago, p1t1o said:

You will find next to nothing about it on the internet, care to guess why? It is *extremely* manouverable in the descent. There is sufficient science in the public domain to be fairly sure that this technology exists, works, and is highly classified. Whether or not it is actually deployed is anyones guess, but its a real thing - manouverable RVs are very possible.

Something like this is being tested since 1960s.
http://rvsn.ruzhany.info/ss_4_8_1.html

P.S.
(The 3rd attempt to post this. I'm sorry if this post will be triple.)

[magnemoe]

1 hour ago, p1t1o said:

1. MIRV =/= MRV

2. ICBMs are more accurate than you think.

3. Getting an ICBM to be that accurate is more difficult than you think.

4. There is a type of reentry vehicle called aMARV, which entered public knowledge several decades ago. You will find next to nothing about it on the internet, care to guess why? It is *extremely* manouverable in the descent. There is sufficient science in the public domain to be fairly sure that this technology exists, works, and is highly classified. Whether or not it is actually deployed is anyones guess, but its a real thing - manouverable RVs are very possible.

Here is a picture of aMARV executing a pull-up manouvre during reentry:

This, as you say, early missiles was inaccurate because of multiple reasons, control systems most of all.
More modern one are far more accurate, an accurate ICBM  warhead is capable of destroying an enemy missile in an hardened bunker while carrying multiple small warheads. 
Now the US put this on submarines, this scared the USSR a lot since the US could launch this from the arctic close to Russian coast giving them an short flight time. 
This scared USSR a lot as it would let US do an very devastating first strike. It did not matter if the US deployed this or not as it was no way for USSR to check. 

Today accuracy is way higher, China has non nuclear IRBM for targeting warships. US has discusses ICBM as rods from god or deep penetrating bombs. 
You don't need 5 meter accuracy with an 100Kt nuke. 

[kerbiloid]

2 minutes ago, magnemoe said:

China has non nuclear IRBM for targeting warships.

Or claims that has.

[p1t1o]

Reports are mixed. It is definitely possible. There are also mixed opinion about how tactically usefully they would be in reality, shooting a ship in the middle of the ocean, from land, is not a trivial ask. On the other hand, sinking an aircraft carrier would go a very long way towards ending the war in your favour in very short order.

Its risk/reward. Do you sail your high-value assets into their range if you only *think* they cant shoot you? Those missile might fulfil their objective without ever leaving the ground.

What is certainly true, is that China has a very large arsenal of conventionally tipped ballistic weapons, which nobody on Earth is particularly happy about. Some of them, so-called "Guam-Killers", are specifically designed to reach US bases. And they are *all* capable of being retrofitted with a nuclear weapon (Or a chemical/biological weapon but that is sooo 1980)

[kerbiloid]

21 minutes ago, p1t1o said:

It is definitely possible.

It was possible before it became mainstream (R-27K, 1975).
http://bastion-karpenko.ru/d-5-r-27k-brpl/

Spoiler

The thing under warhead is a radar antenna. Extends aside.

[magnemoe]

5 hours ago, kerbiloid said:

It was possible before it became mainstream (R-27K, 1975).
http://bastion-karpenko.ru/d-5-r-27k-brpl/

  Hide contents

The thing under warhead is a radar antenna. Extends aside.

Interesting. 
https://en.wikipedia.org/wiki/Pershing_II had an integrated radar.
Now hitting an moving target is far harder add that you can jam radars and that US ABM systems prefer to engage outside the atmosphere. 
However we have moved past traditional ICBM and all stuff is classified. 

[Cheif Operations Director]