If you’re gliding from the peak height, with a constant, given glide ratio, then you’d want to “toss” straight upwards, since that’ll give you the greatest peak height.
Again, of course, nothing’s ever that simple. The glide ratio probably depends on, among other things, the horizontal component of the velocity. And also on things like the air currents between the launch point and the target: A skilled glider pilot can stay in the air all day, by finding thermals and other updrafts and climbing in them.
Pretty dang close to the claimed 80 km range and 32 degree launch angle I saw somewhere else. I’m impressed! And flying at high speed close to the ground, climbing to 6000’ and diving back down would make time the launching aircraft is exposed relatively short unless the AA systems are better than I think they are (entirely possible).
Thanks for working through this. It’s outstanding work. I like that its results line up well with real-world specifications.
This reinforces the point that the JDAM-ER can be super effective in allowing the Ukraninian Air Force join the fight without signing into a suicide pact.
The Russians still have counters, of course. I imagine that the inbound glide bomb is still a pretty good target for modern air defenses, and GPS guidance is vulnerable to jamming, both of which the Russians have plenty of. But not enough to cover every target worth attacking. I suspect with the Russians’ sketchy field logistics, medium-depth targets supporting the immediate battlefront will be good valuable targets. Stuff like artillery emplacements and field depots.
The energy may be the same, but the momentum is different - energy as scalar, momentum a vector.
Toss the unpowered bomb out low
and flat and the glide path will intersect the ground much sooner than if you toss out at altitude or pointed upward. Both is even better. Ideal ballistic angle is as Chronos said, 45 deg.
Glide bomb isn’t ballistic and real world problems affect the result. Still, higher and pointed generally up is better.
But with gliding, no forward power, you would slow quickly to an optimum glide speed which I suspect would be quite slow relative to the 600mph jet speed, since foward motion is created by gravity. Too fast and you drop fast also, too slow and you’re a sitting duck (just like a Cessna 150) It’s a trade-off, like always.
Updating the script to input the launch angle rather than having it calculate the optimal launch angle to see what happens when you launch the bomb nearly straight up (all other factors remaining the same):
Enter projectile mass (kg): 317
Enter initial height (m): 1828
Enter initial velocity (m/s): 330
Enter launch angle (degrees): 85
Part 1: Max height, horizontal distance traveled at max height, and forward velocity at max height
Max height: 6248.15 m
Horizontal distance at max height: 722.24 m
Forward velocity at max height: 23.16 m/s
Part 2: Total range
Total range: 15475.83 m
As you can see, the range is significantly reduced, even though the glide phase starts much higher. With a glide ratio of 8:1 (the wings are rather stubby), you need that speed to cover more ground.
Yes, but maximum time in the air isn’t the goal. Its maximum range
It could be on the winged version. The best ratio will be at a given speed and that speed could be controlled by using a controllable elevator on the tail of the bomb. High angle of attack until it slows to best glide speed and then adjust as necessary from there. That speed would likely be very low, making the bomb a sitting duck. Like md-2000 said, everything is a trade off. I’m no war monger but I’d like to see these JDAMs used to their maximum potential against the Russians.
Not to quibble (OK, I’m quibbling) but that is true only to a certain extent. My quite-slow glider has two different speeds for maximum range (57 kts) and slowest rate of sink/maximum flight time (46 kts.) So, from any given altitude I can choose to fly the furthest distance and meet the ground sooner or fly the longest time and meet the ground closer. For a draggy, stubby-winged bomb these two speeds might be so close that the difference is insignificant but flight time is not range unless speed is a constant. If the flying (as in wings) bomb has any elevator, control speed can be controlled to some degree. No wings? Then, like you said, altitude is the deciding factor.
The elevator. Pulling back on the stick increases the wing’s angle of attack and slows the airspeed. Too much back stick and the wings stall. Push forward and the nose drops, AoA decreases and the speed increases. Too much forward stick will increase the speed until bits start breaking. These are pretty subtle changes in the elevator position but can greatly impact performance. With the aid of trim, holding a particular speed is fairly easy.
Ok, i see what you’re saying. Thanks for explaining.
If I understand, if you pull back on the elevator and use angle of attack to decrease sink rate, the speed will drop and thereby the range as well. Don’t drag as much and you’ll go faster and thereby farther, but will also reach the ground sooner.