Korean Missile Trajectory

[rogerinnh]

The North Koreans are about to launch a missile. Several US officials are making statements like "This missile will either place a payload into orbit, as the North Koreans are claiming, or fall into the Pacific Ocean. It does not have the capability of reaching Hawaii or the East Coast." How can that be? How can it be capable of reaching orbit but not be capable of reaching Hawaii or the East Coast?

 

[MeteorWayne]

I agree that makes no sense. Can you tell us where you heard US officials are making those statements?

 

[rogerinnh]

I agree that makes no sense. Can you tell us where you heard US officials are making those statements?

On CNN and on Fox news. I sent an email to cnn.com about this, hoping they might pickup on it and address it in some upcoming news item. I wasn't able to find an email address for Fox. Maybe if they get enough inquiries about this they'll ask these US officials to explain.

 

[MeteorWayne]

Thanx, I'll check out their stories...

 

[aphh]

There may be some science background to such claimes.

Let's take Shuttle, forexample. If for some reason Shuttle is not capable of accelerating to orbital velocity, the ballistic trajectory makes it land in Europe, not half way around the world.

Either Shuttle reaches orbital velocity and stays on orbit or flies on a ballistic trajectory a few thousand miles downrange at best. Without knowing the missile and it's performance and calculating the possible orbits and trajectories, it is hard to say for certain, so I'm thinking somebody might have the info and has done the math.

 

[rogerinnh]

There may be some science background to such claimes.

Let's take Shuttle, forexample. If for some reason Shuttle is not capable of accelerating to orbital velocity, the ballistic trajectory makes it land in Europe, not half way around the world.

Either Shuttle reaches orbital velocity and stays on orbit or flies on a ballistic trajectory a few thousand miles downrange at best. Without knowing the missile and it's performance and calculating the possible orbits and trajectories, it is hard to say for certain, so I'm thinking somebody might have the info and has done the math.

It appeared, however, that what the officials were attempting to do was to assuage any fears that the North Koreans might have the capability of hitting the US by way of their rocket capabilities. But, if their rocket can actually put something in orbit, as they're claiming, then the orbiting object, whatever it is, could also be made to come down from orbit anywhere they want along the orbital path. It only takes a little bit of retr-rocket thrust to break out of orbit. If that path takes it over the US then of course it could be made to hit the US. And it seems to me there are darn few orbital paths that do not at some point pass over some part of the US.

 

[bobw]

Either Shuttle reaches orbital velocity and stays on orbit or flies on a ballistic trajectory a few thousand miles downrange at best.

I thought without a second burn to circularize the orbit all such launches would smack back into the earth where they started. If the NK rocket is going to make a second burn it should be able to come down anywhere in its orbital plane shouldn't it?

 

[MeteorWayne]

I don't believe that's correct. It is in orbit before the second burn, but in an eccentric orbit with a low (but not ground intersecting) perigee. The second burn circularlizes the orbit near the apogee (high) point.

 

[aphh]

I thought without a second burn to circularize the orbit all such launches would smack back into the earth where they started. If the NK rocket is going to make a second burn it should be able to come down anywhere in its orbital plane shouldn't it?

Few objects that are launched to space have the capacity to do a controlled de-orbit. You need fuel, thrusters, navigation and guidance, software, etc. All this adds costs and reduces payload capacity and is thus most of the time omitted. This is why we have space junk accumulating on orbit.

An ICBM is launched to a high apogee orbit during powered section of the flight. The perigee of the orbit resides inside the earth so the missile intersects with ground where it is supposed to land.

I agree that authorities may have tried to prevent people from thinking they are being targeted by NK, but without knowing the missile and it's capabilities it is impossible to say what is correct.