Is a satellite-launch rocket just an ICBM w/o a warhead with different aiming? (Iran's first...)

See “Iran Launch Forthcoming” (

Closely related, and you *can *use one for the other, but they have different design considerations so in practice tend to be different. Such as ICBMs being designed for instant all-weather launch, and satellite launchers not being designed that way.

…and many of the first satellite launchers from the 1950s and early 60s were basically modified first-generation ICBM or IRBM boosters with an orbital stage or two on top. But as Der Trihs indicates the designs have become each optimized for their particular task.

For that matter, the Soyuz launcher is a direct descendant of the R-7 Semyorka ICBM. And the Atlas rocket family descends from the SM-65 Atlas missile. (It’s a bit ironic that American astronauts now ride the Soyuz, and the current generation Atlas rocket uses a Russian engine in its first stage.)

The Gemini astronauts were fired into orbit on a Titan-II. A derivative of the earlier Titan ICBM. Of which further derivatives were still in use through 2005:

The other consideration - first-generation nuclear weapons tended to be quite large Google pictures of Little Boy and Fat Man). It may be several years even with out-in-the-open development before Iran or North Korea could build a reliable atomic bomb tht fits on one o their (reliable?) rockets. The original sputnik, for example, was pretty light.

Large ballistic missiles are frequently used as the basis for satellite launch vehicles; in fact, most of the launch vehicles that have been flown started life as ballistic missiles or components therefrom, e.g. the PGM-11 ‘Redstone’ (Mercury-Redstone), PGM-17 ‘Thor’ (Long Tank Thor, Thorad, Thor-Delta, and Delta II), LGM-25 ‘Titan II’ (Titan II GLV, Titan II SLV, Titan IIIA/B/C/D/E, Titan-34D, Titan IV) , SM-65 ‘Atlas’ (Mercury-Atlas, Atlas SLV-3), LGM-30F ‘Minuteman II’ (Conestoga I, Minotaur I), and LGM-118A ‘Peacekeeper’ (Minotaur IV/V). Similarly, the Soyuz and Proton rockets are derived from incident heavy ICBMs, and the SS-9 ‘Scarp’ (Tsyklon) SS-18 ‘Satan’ (Dnepr) and SS-19 ‘Stiletto’ (Rokot) are adapted directly form ICBM systems. A nation or entity capable of producing one can make the other. However, ICBMs are designed for high launch availably and robustness against threats, and generally fly a highly elliptical suborbital trajectory (though the SS-18 was specifically designed to fly a fractional orbit) whereas satellite launch vehicles (SLV) generally fly a trajectory approximating a logarithmic spiral into an orbital insertion and are optimized for the greatest payload mass ratio.

In terms of guidance, navigation, and control (GN&C) a accurate ICBM requires a much more precise guidance system than the typical LEO and MEO insertion, which was a major part of the development for modern ICBMs and SLBMs like Minuteman II/III, Peacekeeper, and the Trident C4 and Trident D5. The precision of a high accuracy ICBM guidance system is roughly comparable to that required for geosynchronous orbit insertion. So a nation capable of building an LEO launcher has the propulsion capability but probably not the precision required for a high accuracy intercontinental weapon delivery system.


Which raises an interesting point about the political value of accuracy. And brings the tech back to Leo’s underlying question: what does this mean for politics?

We built very high accuracy systems because we were interested in counterforce targeting. e.g. Blowing up a sub base with a direct hit. Or digging enemy ICBMs out of their silo fields.

If you’re happy landing someplace nearby (say Iran to Tel Aviv county) the accuracy requirements are not so great.

And if you’re happy simply landing anywhere in a large country (say NK to USA or Iran to Britain) the accuracy requirements are even further reduced.

The political utility of being able to threaten the other side’s homeland at large is really all the benefit a smaller power needs. They can’t rationally think of their missile weapons as being effective counterforce combat tools. Their opponents are so much bigger and more capable that an overwhelming response is all but assured.

My point being that perhaps LEO-levels of GN&C may be plenty sufficient for their strategic goals for their weapon systems. I don’t know actual typical LEO nav precision and what influence that precision would have on a sub-orbital mission’s CEP*.

That’s a politico-military observation, not strictly a technological one. Nuclear calculus is a vile business.


  • Why do we call it CEP when the error pattern is actually a very eccentric ellipse? Mostly joking here but it’s always struck me as funny.

To Leo.

You asked a similar question years ago, and Stranger
gave lenghty answers as to why BM can be made into SLVs, but the converse is not true.

Was’nt it rumoured that several US and Russian ICBM’s carried satellites rather than watheads which would launch into orbit and give launch orders to strategic forces?

It bears consideration that nuclear weapons are really a political bargaining chits rather than battlefield weapons. This is true regardless of the size of the arsenal. The degree of precision is important in term of counterforce capability, but to be honest, counterforce has been a non-issue for strategic powers since the development of effective early warning systems. The ostensible accuracy of a system is less of a consideration than the overall impact that a nuclear exchange could have, both in terms of practical losses and the perception of vulnerability. This is why there is the rationale that it is acceptable to spend many tens of billions of dollars on a missile defense system with a questionable capability to intercept an attack by a “rogue nation” with a limited arsenal with very restricted range and accuracy.

Most of the error in ballistic missile systems is actually in the dynamics of the reentry vehicle. The error is modeled as a Gaussian distribution with single variable (radius), which is close enough to flight test results to be an accurate measure of accuracy.


Well yeah, rockets are rockets. Whether it’s military or civilian it’s still all about specific impulse, Delta V, payload weight etc. One difference you could point out is that ICBMs are always suborbital. Once you can hit the other side of the Earth you can pretty much hit anywhere. And the 60s treaty banned nuclear orbital launch platforms. Payload is still a big factor because making powerful nukes lightweight (particularly H-bombs) is still difficult for less-developed countries (even those that have nuclear bombs already).

But the manned, orbital Gemini capsule was much lighter than the multi-megaton warhead that the Titan was designed to launch (suborbital).

Agreed. My point, which you’ve corroborated, is that powers such as Iran or NK simply need reliable launchers & reliable warheads. Accuracy is nice-to-have, not need-to-have.

Which means Iran and NK are that much closer to politically useful anti-regime-change weapons. Which will reassure dear **Leo **no end.

Not a rumor, but not a satellite either:


Colour me surprised; how did it work? Just go up and transmit “Russia can go straight to hell”? while falling down?

(I thought the Minuteman II could easily place its payload into orbit and the PBV could act as an orbital insertion motor?)

ECRS basically flew in a retrograde trajectory transmitting launch authorization signals for the few minutes it took to fly across the continental United States. Placing the transmitter into a prograde (eastward) orbit would not be useful. In operation, Peacekeeper, Minuteman III, and the Poseidon and Trident SLBMs do not place the post-boost vehicle (PBV) into a stable orbit; it is lofted to a high elliptical orbit and then the reentry vehicles (RVs) are released individually to different targets to increase coverage and potential for avoiding interception. Most PBVs have pretty minimal impulse; they’re really designed to provide a final nudge to send individual RVs at independent targets. (MMII was a single RV launcher and did not have a PBV.)


[Note which should be posted every few years:

For the umpteen threads like these, where the hell would we be without Stranger On A Train?


Carry on.

Stranger, could you give some more detail on these trajectories? In particular:

  • Why is a highly elliptical trajectory suited to ICBMs?
  • What is a fractional orbit?
  • Why is a logarithmic spiral suited to orbital launch?

Thank you. Should’ve bumped that one.

That was a good thread. I’ll pretend I didn’t forget it or its contents, and thank you for that SD cite and the next one as well.

A high elliptical trajectory gives the fastest reentry speed and
most optimal throw weight per vehicle total impulse. The downside is that is spends more time above the horizon where it can be seen by early warning radar systems. (Since major strategic powers have satellite early warning systems that can detect a missile launch from ignition, this isn’t as much of a concern except in terms of vulnerability to a hypothetical mid-course missile interception system.) Some missiles–particularly SLBMs–fly depressed trajectories, where they trade reduced range or throw weight for less time above the horizon and faster overall response.

Land based ICBMs (and the Soviet SLBMs) typically launch in trajectories that cross the Arctic circle, hence the DEW line faced north. A Fractional Orbital Bombardment System (FOBS), however, can be launched into a different orbit coming from an unexpected direction such that it looks like a satellite until it gets into position to launch the RVs. With the expanded coverage of the BMEWS fence and DSP satellites detecting and tracking launches from essentially anywhere, FOBS became less attractive. (The Soviet Union developed a couple of FOBS capable systems but it is unclear as to whether they were ever deployed operationally.)

Most of the speed needed to achieve orbit isn’t up away from the Earth’s surface but tangent to it; hence, an orbital trajectory will have a vehicle that initially flies up (to get above the densest part of the atmosphere) and then pitches over (generally using a gravity turn) to gain orbital speed. The resulting trajectory looks approximately like a logarithmic spiral. In general, to go to a higher orbit, you thrust “forward” (in the direction of orbital travel) rather than “up” (normal to the Earth’s center of mass). For an ICBM, however, you mostly want to expend your energy going up (so you can come down as fast as possible) and only going forward as much as necessary to achieve the desired range. In more straightforward terms, for an orbital launch vehicle you want your trajectory at separation to fall above the horizon with enough tangential speed to maintain an orbit; for an ICBM, you want it to run back into the ground well below the horizon with as much radial speed as possible.