I recently went on a tour of a decommissioned Titan II ICBM missile facility (this one, which which was very a very interesting and well done tour, and I’d very much recommend it to anyone interested in this subject). During the tour, it was mentioned that the ICBM trajectory went as high as 800 miles above the ground. This seems like an awfully high parabola to reach a target in (presumably) the USSR from the U.S./Arizona, considering the ISS orbits at ~200 miles.
My question: was 800 miles the necessary trajectory to economically reach a target around the world, or was it decided for some strategic reason to ‘throw’ the missile high, perhaps for attack angle or some other reason?
Well, here’s my WAG: the ISS is not expected to evade detection nor obliterate Moscow. ICBMs are supposed to do these things, if they work as advertised.
So presumably they take the shortest tactically safe 3D path, which might well involve avoiding things like satellites that are there to figure out if an ICBM is attempting to evade detection in its quest to obliterate Moscow. Since rockets don’t need an atmosphere, I’d imagine that if the safest and fastest path involved reaching 800 miles altitude, there isn’t much to prevent such devices from utilising that path.
PaulParkHead: I was surmising something like that as well – they wanted to ‘throw’ the missile high to avoid detection, or confuse trajectory analysis or… something. perhaps from 800 miles up they could reach half the globe w/o telegraphing where the missile would ultimately land?
. . . note, the key point is “as high”. I don’t have my orbital mechanics book with me right now, but I don’t see it out of the realm of possibility that flinging a nuke from Arizona to Siberia might take that kind of height.
Now, with most of the missiles in Montana, North Dakota, and Wyoming, that height may not be as high, but they are ‘ballistic’. The boosters kick 'em up so high, then they essentially fall back down to earth. Sounds to me like they were taking a little license with the actual apogee of the flight. . .
Tripler
. . . a little free license for ‘dramatic effect’–as if nuclear war needed more drama. :dubious:
“The world as we know it could end in a nuclear holocaust. The human survivors will live as troglodytes and eat cockroaches. But just to make it a little less tedious…”
That was my basic thinking. I started from my inexpert airplane geek perspective. A jet can go faster if it can go higher, to a point, but eventually it, um, runs out of air. Now presumably one could attach a couple of turbofans to a warhead, file a flight plan and get full IFR clearance at 40,000ft from runway 9L at Philadelphia. But someone just might notice. It could take an hour or two.
Attach these things to rockets, and this is no longer a problem. Now the ISS is expected to remain pretty much in the orbit in which it was placed, and also be reasonably accessible from Earth using spacecraft capable of transporting more than a nuclear warhead. But if all we want the thing to do is go up and then come back down where we tell it to, and ideally giving as little warning as possible of its arrival, well…
A follow-up for Tripler or anyone else - take a Shuttle orbiter. My understanding is that it reaches orbit using rockety things, stays there for a few days while the crew do their spacey stuff, and then returns. On return it requires a small amount of engine power, but that is to slow down the orbiter on re-entry. After that part is safely accomplished, the orbiter essentially acts as a glider, drifting towards some long airstrip in Arizona where they have time to deal with frivolous nonsense like expanding the frontiers of human knowledge - everyone else being too busy getting ERJs out to Fresno and Memphis.
OK, actual question: what stops these ICBMs from burning up? Do they pull similar maneouvres?
The re-entry vehicles are covered in an ablative material, like carbon-carbon composites. They re-enter the atmosphere at hypersonic speeds. Unlike the Shuttle, there is no need to slow down to subsonic speed for a safe landing. I’ve seen some ICBM tests and the incoming re-entry vehicles look much like meteors. They are moving very quickly.
Nope, so long as “the device functions”* that’s all that matters. I believe the shape of the RV has a lot do do with shedding the heat from reentry. As mks57, said, the shuttle has to brake. RVs, you don’t exactly want dallying about.
Tripler
*Note: These are the exact words the missileer used. Pretty cold, but hey, that’s war.
I’ve done quite a bit of energetic materials testing, and worked with a lot of weapons design engineers. 99.9% of the time, the fact that you’re designing, building, and testing something that has the sole purpose of killing people and destroying property doesn’t even enter the thought process. “How can I make the flight more stable,” “Is this casing thick enough to penetrate x feet of concrete, and are the right sensitivity of accelerometers in the timing package to ensure detonation at the expected time,” and the like are things the designer is thinking. I wouldn’t consider it being cold hearted, it’s just another day at the office.
Sometimes I get a moral pang, thinking what I do is wrong. But, two thoughts immediately enter my mind to appease them. First, if I wasn’t doing it, somebody else would be. Second, seeing things go boom is really effin cool! I’ve done a lot of work setting up training exercises for first responders, and quite a bit testing retrofits of structures to withstand terrorist blasts.
The biggest test series I was ever involved with was during the design phase of the new ATF headquarters. From that site:
I thought this was funny, because the testing I was involved with assumed those barriers weren’t there. The specific test series was only for the glass curtain wall behind those “big ugly barrier walls”.
“May all our devices explode. Over the test ranges but not over cities”
The reason the balistic missiles are launched up so high is that you consume less fuel by going up fast, with the shortest path through the atmosphere. They don’t need to stay in orbit.
Have you noticed shuttles taking off and their trajectory is slowly bending back behind the horizon - they have to expend a huge amount of fuel to build an orbital momentum if they want to stay up there. But if they just went up and fell back down like burtans Airship One they could be much, much smaller.
Nitpick–first generation RVs, like the AVCO Mark IV, had a big metallic thermal mass (mostly alloyed copper) to absorb heat. The very tip of modern ICBM RVs is usually a reinforced carbon-carbon (RCC) material, but the main body of the RV is typically some kind of high temperature carbon phenolic tape lay-up. It is necessary to prevent ablation of the main body as much as possible because even slight geometic irregularities in the surface can result in undesirable spin or yaw impulses that will make a purely ballistic RV become inaccurate or unstable. The nosetip essentially sets up a shock wave which helps prevent ablation and convective thermal transfer to the main body. Older RVs like the Mark VI had a blunt body shape which helped to create a larger shock wave and allowed a larger payload (the Mark VI carried the 9MT W53 warhead on the Titan II, the largest ICBM nuclear package deployed by the United States) but was rather slow, making it vulnerable to interception, and tended to be less accurate. More modern RVs like the Mark 12A and Mark 21 used on Minuteman II/III and the now deactivated Peacekeeper have a more acute profile and a smaller tip, which allows much faster reentry (as mks57 says, they’re coming in faster than the eye can track) but requires careful design to prevent uneven tip erosion and loss of stability. There are also maneuverable RVs under development (and allegedly deployed by the Russians) which have articulating aerodynamic and lifting body surfaces, again presumable a RCC structure, that allow it to maneuver to avoid intercept or follow a non-ballistic terminal trajectory (useful for striking targets protected by ground features).
As for the OP’s question, the general scheme for a suborbital ballistic track is to get it to the target as quickly as possible. There may be other considerations, such as minimizing the probability of intercept or detection, which dictate other trajectories, like a fractional orbital trajectory used in FOBS or the depressed trajectories used by SLBMs, but in general you want to take the quickest–which is not necessarily the shortest–path, as well as making best use of your limited burn time on the rocket to acheive greatest range. You’d also prefer it to come as straight down and as fast as possible, minimizing time in the atmosphere (where aero loads will decrease the accuracy of the purely ballistic RV) and probability of terminal intercept, and the higher up it is during the mid-course flight, the harder it will be for a missile interceptor based in the target geography to reach. 800 miles isn’t really all that high when compared to the radius of the Earth; the problem with putting a payload into orbit at that altitude isn’t getting it up there, but generating enough orbital momentum to keep it in a stable orbit.
Orbital mechanics point of note: although the trajectory of the RV (once the rocket burns out and the RV is released) is strictly ballistic, it isn’t in the shape of a parabola unless you play some tricks with the geometry of the space it flies through. The shape of the orbit is actually an ellipse that intersects the surface of the planet. A parabolic orbit would actually have it in an escape trajectory, and it would never return.
There is a lot of creepily euphamistic terminology surrounding nuclear weapons and strategic weapons systems intended to conceal the fact that these are all weapons designed with the ostensible purpose of executing genocidal-scale death and destruction. Reducing the concepts to statistics and game theory concepts allows one to discuss them without sounding like General Turgidson, walking around with his arm protectively curled around binders entitled “World Deaths In Megatons” and making pronouncements like, “Mr. President, I’m not saying we wouldn’t get our hair mussed, but I do say that no more than ten to twenty million killed, tops…ur, depending on the breaks.”
Just to add on, if you shoot something straight up out of the atmosphere, it doesn’t come back down to where you launched it. It comes down some place to the west. Basically, instead of aiming to the West, you shoot it straight up and the Earth rotates undernearth it.
Not necessarily . . . we learned about this in my one orbital mechanics class. IIRC, almost all of the tracks are eastbound to take advantage of the already-present angular velocity inherent on being launched from a rotating sphere. The best locations for maximizing that inherent velocity–the equatorial regions where your velocity is at it’s greatest.
Now, you’re right in the sense that on launch and adjustment to compensate for the inherent velocity, the earth would in effect rotate 15 degrees each hour underneath a “stationary” satellite. In your example of “straight up”, the closest practical example you have is a polar orbit–instead of orbiting the earth in an east-west fashion, you orbit the poles. But then again, you get your 15-degree shift.
I have a couple of links that show good ground tracks. . . let me dig 'em up.
Tripler
I once studied rocket science. But that was in pursuit of my Doctorate of Cool degree.
