Ground Based Interceptor (GBI)

Trident said:
I was certainly NOT suggesting that it did! And as BGRV itself is unpowered, I'm not sure how you'd effect release before the Atlas has burned out...
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Throttle back and let drag slow you down while you release the vehicle.
 
Forest Green said:
sferrin said:
ALL HGVs have boosters. They don't just teleport themselves to flight conditions. And yes, it flew 8,000 km in 45 minutes, and while it did slow down from weapon release to impact 8000km later, it was still traveling at high hypersonic speeds at impact.
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Wasn't there also a booster (i.e. propulsion) integrated on the BGRV itself though? That was my understanding anyway.

sferrin said:
The thing did not remain attached to Atlas the entire flight. "Burnout" velocity of Atlas is irrelevant. Release velocity (Mach 15) is what matters.
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This paper (page 9) states a maximum range of 4,000km gliding at a much high altitude with an entry speed of 5km/s, which is approximately Mach 15.

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You're mixing up vehicles. BGRV demonstrated a range of 5000 miles.
 
sferrin said:
Thrusters for directional control. The thing was no more powered than a KKV axially.

View attachment 691283
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Were the nozzles pointing rearward though? It may have helped slightly. I don't understand how it managed 5000 miles (8000km) with a Mach 15 injection speed otherwise.


1673976522580.png

sferrin said:
You're mixing up vehicles. BGRV demonstrated a range of 5000 miles.
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But how? That's twice the distance in the study for a Mach 15 (5km/s) start. And the BGRV is clearly a cone, rather than some advanced lifting body, and it did an 'S' manoeuvre, and started at only 40km altitude. Something is amiss.
 
Forest Green said:
But how? That's twice the distance in the study for a Mach 15 (5km/s) start. And the BGRV is clearly a cone, rather than some advanced lifting body, and it did an 'S' manoeuvre, and started at only 40km altitude. Something is amiss.
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Mach 15 is 15,9km/sec. Way off your table. And every unique design will have a different set of curves.
 
sferrin said:
Trident said:
I was certainly NOT suggesting that it did! And as BGRV itself is unpowered, I'm not sure how you'd effect release before the Atlas has burned out...
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Throttle back and let drag slow you down while you release the vehicle.
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The Atlas-F's engines couldn't be throttled, the only way to reduce the thrust of the MA-3 rocket-motor assembly would be to shutdown the two booster engines and seperate the thrust structure leaving just the sustainer rocket-motor and vernier thrusters burning.
 
sferrin said:
Throttle back and let drag slow you down while you release the vehicle.
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Why would you though? You're not trying to do a precision orbital insertion where a couple m/s one way or the other affects the orbit, arguably you want to impart the HGV with all the kinetic energy you can. Any inaccuracies in release parameters can be later compensated for by aerodynamic maneuvering.

sferrin said:
Mach 15 is 15,9km/sec. Way off your table. And every unique design will have a different set of curves.
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No it isn't - 5.5km/s is actually about right, give or take depending on whether you use the speed of sound at sea level or 40km and how warm a day you assume, as well as how much "more than Mach 15" really is. And that does call into question what's happening here, I'd suggest it's another indication BGRV did in fact leave the atmosphere and only reenter about 2000km downrange. That fits well with the 5.5km/s HGV trajectory in the HGV paper that hits almost 6000km *glide* range (not total flight range).

Forest Green said:
This seems to mention control jets behind the flare (page 167)??

Page 168:

Control was provided by a 12-piece, segmented, variabletrim
flare and small rocket thrusters mounted on a spherical
aft end behind the flare. Individual control flaps, as depicted in
the NACA glide vehicle concept in figure 9, could not withstand
the severe heating, so the flare/thruster system was designed.
The flare changed the vehicle trim angle of attack, and the
thrusters provided angle-of-attack transient control. Like the
122B Alpha Draco, the 122E was slowly rolled to provide uniform
heat distribution. Guidance was provided by an inertial
navigation system and digital computer.
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Well, you've answered your own question there, right? The thrusters were for control only, not propulsion.

Forest Green said:
A single Avangard uses an SS-19 which is 2.5m diameter and 27.5m length and weighs 106t, which is larger and heavier than a Minotaur V, which can send half a ton to the moon.
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SS-19 is a two-stage vehicle, while Minotaur V has no less than 5 stages! This is admittedly also a flaw in my FOBS comparison though, as R-36O is also two-stage (as opposed to three-stage like Trident) negating the liquid propellant advantage. The LADEE lunar probe also weighed only 380kg and had to expend some of its own propellant to complete the TLI burn (arguably making it a 5.5-stage vehicle), so actual Minotaur V payload to the moon is considerably less than 500kg - more like a third of a ton.

Forest Green said:
A Minotaur IV can put 1735kg into a LEO orbit, but weighs only 86t (presumable minus payload), and is only ~2m taller than an LGM-118, same width. Figure 9 seems to show an injection speed of ~7.5km/s for 8600km on a depressed trajectory, orbital speed is ~7.8km/s at 185km altitude. So a Minotaur IV sized ICBM should be able to complete an 8,600km throw with about half an LGM-118's full load (3580kg), and since we're limited to 4 warheads these days, that's not a problem anyway.
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Again, stage numbers. A three-stage missile isn't going to match that performance.

Forest Green said:
Well that is the nature of a fast delivery, yes, but you could probably do the same with an ICBM MaRV but the warning time would obviously increase, and I guess you would have to program it with some way of knowing when to manoeuvre, so as not to waste fuel.
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We're not interested in fast delivery though - what advantage there is over a MET is merely a side-effect of outflanking exo-atmospheric mid-course BMD.
 
sferrin said:
Mach 15 is 15,9km/sec. Way off your table. And every unique design will have a different set of curves.
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Woah, your maths is out there. Speed of sound is 340m/s at ground level and about 295m/s at 20km. At 40km (130,000ft) it's 316m/s. So around 4.74km/s.

1920px-Comparison_US_standard_atmosphere_1962.svg.png
 
Trident said:
Forest Green said:
This seems to mention control jets behind the flare (page 167)??

Page 168:

Control was provided by a 12-piece, segmented, variabletrim
flare and small rocket thrusters mounted on a spherical
aft end behind the flare. Individual control flaps, as depicted in
the NACA glide vehicle concept in figure 9, could not withstand
the severe heating, so the flare/thruster system was designed.
The flare changed the vehicle trim angle of attack, and the
thrusters provided angle-of-attack transient control. Like the
122B Alpha Draco, the 122E was slowly rolled to provide uniform
heat distribution. Guidance was provided by an inertial
navigation system and digital computer.
Click to expand...
Click to expand...

Well, you've answered your own question there, right? The thrusters were for control only, not propulsion.
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Perhaps, but they would still provide some thrust and reduce manoeuvring-induced drag. I was trying to reconcile how it managed 8000km with an injection speed of <5km/s, when the article you posted earlier estimates only 4000km with a proper glide body at higher altitude.
Trident said:
Forest Green said:
A single Avangard uses an SS-19 which is 2.5m diameter and 27.5m length and weighs 106t, which is larger and heavier than a Minotaur V, which can send half a ton to the moon.
Click to expand...

SS-19 is a two-stage vehicle, while Minotaur V has no less than 5 stages! This is admittedly also a flaw in my FOBS comparison though, as R-36O is also two-stage (as opposed to three-stage like Trident) negating the liquid propellant advantage. The LADEE lunar probe also weighed only 380kg and had to expend some of its own propellant to complete the TLI burn (arguably making it a 5.5-stage vehicle), so actual Minotaur V payload to the moon is considerably less than 500kg - more like a third of a ton.
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The quote is 342kg for a Minotaur V according to wiki (I was approximating).

en.wikipedia.org

Minotaur V - Wikipedia

en.wikipedia.org en.wikipedia.org
Trident said:
Forest Green said:
A Minotaur IV can put 1735kg into a LEO orbit, but weighs only 86t (presumable minus payload), and is only ~2m taller than an LGM-118, same width. Figure 9 seems to show an injection speed of ~7.5km/s for 8600km on a depressed trajectory, orbital speed is ~7.8km/s at 185km altitude. So a Minotaur IV sized ICBM should be able to complete an 8,600km throw with about half an LGM-118's full load (3580kg), and since we're limited to 4 warheads these days, that's not a problem anyway.
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Again, stage numbers. A three-stage missile isn't going to match that performance.
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Fair enough, but size-wise the missile is well within the bounds of an ICBM design. And no reason not to use 4 stages. Even a Minotaur I can put nearly 600kg into a LEO. 4 stages but way, way smaller than a Peacekeeper.

en.wikipedia.org

Minotaur I - Wikipedia

en.wikipedia.org en.wikipedia.org

Trident said:
We're not interested in fast delivery though - what advantage there is over a MET is merely a side-effect of outflanking exo-atmospheric mid-course BMD.
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I don't know, a fast delivery has its advantages. If you catch the enemy leader on the toilet, mid-dump, it may prove crucial. :D
 
Range and payload for an HGV are a function of the L/D ratio, injection speed, and injection altitude. Speed and altitude are easy to get from the booster used, but L/D depends on the HGV's configuration, so if you don't know that you are merely guessing.

Space launch vehicles and ICBMs have very different flight profiles and requirements, yes a booster can do both, but there are substantial changes involved.
 
I would not be surprised if they want to reach all the way to GEO. (Assuming GBI can't do that already.)
 
Josh_TN said:
I can’t imagine either having anything like GEO kinetics.
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Depends how heavy the KKVs are, and how many it carries on a given launch.

bobbymike said:
What are the dimensions of the GBI & NGI?
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GBI is 16.61m x 1.28m. So I get 19.9m x 1.9m for NGI by way of ruler. Oddly this would make it the largest US missile in current service.
 
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What a groundbased KKV is thinking in flight:

“That’s the nosecone….that’s a decoy…that’s the MIRV bus…here’s the warhead-whoops! Done passed it!”

Space-based boost phase or bust.

It’s not as if it can deploy Tex Avery toon-brakes and turn around, you know.
 
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publiusr said:
Space-based boost phase or bust.
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;)

breakingdefense.com

Beyond 'bullet on bullet': NORTHCOM's new defense plan looks to kill missiles before they launch - Breaking Defense

"The best missile strategy is to destroy the missiles prior to launch. A focus on missile defeat could enable distributed non-kinetic systems with larger magazines and the ability to engage missiles before they can deploy complex decoys, countermeasures, maneuvers or multiple reentry vehicles,"...
breakingdefense.com breakingdefense.com

The commands’ focus “going forward relies less on kinetic engagement, instead emphasizing non-kinetic means … such as directed energy, electronic attack, high power microwaves, to complement our direct kinetic active defenses.”
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