Yeah, not quite as high, but they still went into orbit. You’re not going to fly from the continental US to the USSR in 30 minutes in the atmosphere. The drag/friction and fuel required are engineering impossibilities until we get into Star Trek territory.
ShivaX
3165
Well, it doesn’t take quite as much if you’re fine with things falling back to Earth at a few thousand miles per hour, but extra altitude is just wasted energy at that point. Better to turn it into speed towards your target area.
That’s not how (sub)orbital mechanics work. Speed is altitude.
ShivaX
3167
Until terminal velocity kicks in.
And it’s not pure speed you’re after, it’s time to target.
If your rocket climbs for 10 minutes and then drops to it’s target and mine climbs for 5 and powers for 5 towards the target, mine is getting there a lot faster (thought it’s more like I fire at an angle, but whatever it’s late). Flying straight up takes a ton of energy. Flying sideways doesn’t. You fly high enough to clear the atmosphere and then towards the target till you’re in range to release the payload.
The warhead is free falling at terminal velocity anyway. No one cares what the rest of the rocket is doing at that point.
Edit: Of course NK isn’t actually trying to hit anything, they’re basically just testing engines, so up works for this.
CraigM
3168
I think you misunderstood @Grunden
When you are outside of atmosphere, even suborbital, going faster will necessarily increase apogee. So if you accelerate forward you are also increasing the maximum height you will reach.
Granted its a bit more complicated and it usually means raising the elevation on the opposite side of your orbital path, which for sub orbital flight mostly means altering the point at which you smack into the ground. So the overall impact on apogee height is greatly diminished versus altering travel distance.
Just to add - NK have the problem that they’re basically surrounded by other countries and their waters, so their only option to test to ICBM ranges is actually to go “up”. I don’t have a link handy but there’s a RAND article or similar which explains how to then translate the altitude of the test into a theoretical range.
Now if we can just convince them to test one of their warheads by launching it straight up and then down on to their own heads…
Right, it’s not like it’s rocket science… oh wait. Flippancy aside, orbital mechanics are weird and full of counterintuitive behavior for those who are thinking in terms of atmospheric flight.
This is the kind of system where if you’re in visual range from a space station in your rocket, and you point it at the station and light up your thruster you get no closer. In fact it starts to drift away faster. Science fiction movies lie!
This was essentially the whole thing with the space race in the late 40’s-50’s. It’s relatively simple to achieve orbital altitude; but getting enough velocity to widen the arc to achieve orbit (sideways movement) was the real challenge.
Right. What we call “suborbital” is still an ellipse, it’s just that a portion of the ellipse is inside the earth but the mechanics work the same outside the atmosphere.
Bottom line is that you can’t just draw a trajectory and say “do this, but faster”. Velocity is integral to the trajectory; every variable affects every other variable. For the same reason, everything in a circularized orbit at a particular altitude is moving the exact same speed; you can’t orbit faster without changing the orbit.
I believe I read the same article. And yes, that whole point of the “high lob” for these tests it to demonstrate the amount of delta-v available to the launch vehicle. We can extrapolate from there that the missile is capable of reaching San Francisco (or wherever).
CraigM
3172
My favorite quirk of orbital mechanics is: you accelerate to move to a higher orbit, where your average velocity is slower. If you want to be in a faster orbit, you need to decelerate to get there.
Every calculus class that doesn’t show the students this example is stupid.
Matt_W
3174
You can if you continuously thrust :)
And to make it even more confusing, your instantaneous velocity is actually higher, which is why when you’re nearby a target in closely matched orbit, you can do docking maneuvers by pointing and thrusting. The difference in instantaneous velocity overwhelms the difference in average orbital velocity for short time maneuvers in nearly flat space.
That’s changing the orbit.
Matt_W
3176
If you thrust prograde and radially downward, you can maintain a circular orbit at a higher velocity than without thrust. Also, orbital velocity at the EML points are exactly equal to the moon’s orbital velocity even though they’re at different altitudes than the moon’s.
But that’s pedantry. You’re right. For ballistic circular two-body orbits altitude completely determines the period.
CraigM
3177
Call me when you invent the Epstein drive then :)
But we all agree that orbital mechanics are weird and counter intuitive in many cases, and that normal aviation intuition is not only wrong, but often actively unhelpful.
Matt_W
3178
Lol. Well, you could do it with Dawn’s Xenon drive… it just wouldn’t be very much faster.
Agreed, and sorry for the thread derail. I can’t resist discussing orbital mechanics. I’ll note that the primary reason aviation intuition is wrong is because aircraft are continuously under thrust–hence my pedantry on the orbital stuff.
We could also equip our missiles with black hole generators, and have the orbit go through the planet. That would probably shave some time off.
That’s not really an orbit anymore, you are in powered flight and plotting your own course. We don’t say airplanes are in orbit.
Lots of room for pedantry in this discussion. You could say you’re in orbit making little suborbital hops every time you take a step. Of course you’re applying thrust to the earth as you do so.
Matt’s scenario is more akin to a continuously changing set of orbits that sum up to overlay the prior orbit.
Physics is fun!
It’s like none of you people have ever played KSP. wtf.
I’m going to reframe everything mundane into weird references to Qt3 topics.
“Did you see that unburied guy making suborbital hops down the street?”
