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Author Topic: Army Wants 'Air Droppable' Light Tank & Ultra-Light Vehicles  (Read 50430 times)

Offline marauder2048

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Re: Army Wants 'Air Droppable' Light Tank & Ultra-Light Vehicles
« Reply #180 on: August 27, 2017, 02:57:26 pm »
It is quite a popular option outside the US. The Israeli Spike series, except the Spike NLOS which uses a wireless link, are all FOG missiles. The new Spike II is especially impressive looking.

Much shorter range than FOG-M and most of the newer Spike II LR versions use an RF datalink.

this was the last completely new tactical missile to enter US Army service.

That would be Griffin.

Offline Void

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Re: Army Wants 'Air Droppable' Light Tank & Ultra-Light Vehicles
« Reply #181 on: September 09, 2017, 07:02:41 pm »
Whether the guidance signal travels over fibre or over wireless does not change the nature of the guidance system. A better term would probably be TV-guided. "Fiber optic guidance" is a misnomer in that sense, just like "wire-guided". The US experimented with the same kind of wireless "FOG" guidance with the FMTI missile.

And as for the Griffin, it was sold on very the premise that it wasn't a completely new missile, but one that reused components from existing missiles as much as possible.

Offline Mach42

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Re: Army Wants 'Air Droppable' Light Tank & Ultra-Light Vehicles
« Reply #182 on: September 09, 2017, 10:29:40 pm »
As an aside, there are rumours of Hanwha Defense Systems teaming up with Lockheed or Raytheon to modify the K21-105 for the MPF program. Hanwha will have a presence at AUSA this year so addition information may be forthcoming then. Seems like a less capable, but low cost and low risk design.

Offline bobbymike

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"I love those who can smile in trouble, who can gather strength from distress, and grow brave by reflection. 'Tis the business of little minds to shrink, but they whose heart is firm, and whose conscience approves their conduct, will pursue their principles unto death." - Leonardo da Vinci

Offline marauder2048

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Re: Army Wants 'Air Droppable' Light Tank & Ultra-Light Vehicles
« Reply #184 on: September 12, 2017, 11:29:47 pm »
Whether the guidance signal travels over fibre or over wireless does not change the nature of the guidance system.

Sure it does; fiber permits much higher bi-directional data rates and much lower latency
which in turn makes things like performing automatic tracking and aimpoint selection on the
launcher-side readily doable.

FMTI was shorter range and fire-and-forget; the 2-way RF datalink had a much lower data rate and, AFIAK,
was mostly for LOAL fratricide avoidance.



And as for the Griffin, it was sold on very the premise that it wasn't a completely new missile, but one that reused components from existing missiles as much as possible.

It was sold on that premise but it really is a new missile particularly the more recent blocks.

Offline Void

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Re: Army Wants 'Air Droppable' Light Tank & Ultra-Light Vehicles
« Reply #185 on: September 13, 2017, 04:02:15 am »
Wireless has a lower minimum latency than fibre. EM waves simply travel faster through air than glass. The bandwidth available is higher in fibre true, but the bandwidth available in microwave or MMW links like the Spike-NLOS and FMTI use(d) is far in excess of what is actually needed for the relatively low-resolution video and missile data. The FMTI wasn't especially short range for its size either, it was tested to 8km (not trivial for a TOW-sized missile with a rocket motor) and had the potential for significantly greater range. And of course, the wireless Spike NLOS has a range of ~25km and seems to work quite well.

The attraction of fibre is the same as the attraction of wire in older missiles: The link is more reliable, especially at long distances, and it is largely immune to hostile interference. The principles of TV guidance did not change when it occurred to someone to link the weapon to the launcher by a fibre optic cable; TV guidance was already well established when optical fibre entered the picture as a potential alternative to radio links.

As for the Griffin, it is not alone in that regard. The Javelin has also been mostly rebuilt, there is a nice picture I don't have right now showing all the components that have been replaced since it entered service and it is almost the entire missile. As has the TOW. And the Hellfire. But they are still not completely new missiles. This isn't even my own observation. US tactical missiles which are not derived from existing missiles have been pretty consistently axed.

Offline Kadija_Man

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Re: Army Wants 'Air Droppable' Light Tank & Ultra-Light Vehicles
« Reply #186 on: September 13, 2017, 05:14:23 am »
All this is very interesting.  However, what it does not explain is why the US Army has been so resistant over the years to the use of optical fibre guided weapons.   FOG-M was quite capable but it was abandoned after the US Army didn't want it.  EFOGM was also abandoned.  Either would have allowed a light armoured vehicle which was quite capable of killing any MBT to be in service decades ago.   

Offline marauder2048

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Re: Army Wants 'Air Droppable' Light Tank & Ultra-Light Vehicles
« Reply #187 on: September 13, 2017, 02:52:15 pm »
Wireless has a lower minimum latency than fibre. EM waves simply travel faster through air than glass. The bandwidth available is higher in fibre true, but the bandwidth available in microwave or MMW links like the Spike-NLOS and FMTI use(d) is far in excess of what is actually needed for the relatively low-resolution video and missile data. The FMTI wasn't especially short range for its size either, it was tested to 8km (not trivial for a TOW-sized missile with a rocket motor) and had the potential for significantly greater range. And of course, the wireless Spike NLOS has a range of ~25km and seems to work quite well.

Propagation delay through the medium is not the major driver for the latency difference.
It's the protocol overhead of making RF datalinks reliable, full-duplex, LPI/LPD/jam-resistant etc.

FOG-M and its derivatives were not low-resolution which was the whole point.
Spike NLOS RF and FMTI are both predominantly F&F missiles with a MITL datalink
for LOAL.

The principles of TV guidance did not change when it occurred to someone to link the weapon to the launcher by a fibre optic cable; TV guidance was already well established when optical fibre entered the picture as a potential alternative to radio links.

Auto-tracking and automatic target handoff correlation (along with CCDs) revolutionized TV guidance in the late 70's.
But it was impractical (certainly at cost) to realize those gains over RF.

But they are still not completely new missiles. This isn't even my own observation. US tactical missiles which are not derived from existing missiles have been pretty consistently axed.

The slide-deck predates Griffin. And by the definition above FOG-M wouldn't have been
considered new because it used TOW's motor.

Offline marauder2048

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Re: Army Wants 'Air Droppable' Light Tank & Ultra-Light Vehicles
« Reply #188 on: September 13, 2017, 06:38:08 pm »
All this is very interesting.  However, what it does not explain is why the US Army has been so resistant over the years to the use of optical fibre guided weapons.   FOG-M was quite capable but it was abandoned after the US Army didn't want it.  EFOGM was also abandoned.  Either would have allowed a light armoured vehicle which was quite capable of killing any MBT to be in service decades ago.

My view is that the theme has been:

Fire-and-Forget approaches (especially with IFTU) tend to kill or relegate FOG even in the non-US offerings.

In the 80's, only Army Air Defense had the budget for FOG-M  and primarily as an anti-terrain masked helicopter weapon. 
Even then, a surface-launched AMRAAM was considered for that role.

In the 90's, Longbow Hellfire consistently outperformed EFOGM.

I could see FOG making a comeback in the ISR role though.

Offline Void

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Re: Army Wants 'Air Droppable' Light Tank & Ultra-Light Vehicles
« Reply #189 on: September 14, 2017, 05:50:35 am »
Propagation delay through the medium is not the major driver for the latency difference.
It's the protocol overhead of making RF datalinks reliable, full-duplex, LPI/LPD/jam-resistant etc.

But this is not a fundamental characteristic of a wireless link. The amount of interference it would be expected to encounter, intentional and unintentional, and the degree of covertness required would be application specific. For a given set of requirements, fibre may well prove to offer no meaningful advantage.

FOG-M and its derivatives were not low-resolution which was the whole point.
Spike NLOS RF and FMTI are both predominantly F&F missiles with a MITL datalink
for LOAL.

The video format of the FOG-M was RS170. Calling it high resolution is a bit of a stretch. The current Spike-NLOS provides CCD, IIR and SAL feeds simultaneously, which was beyond any hardware that existed in the FOG-Ms time.



The Spike-NLOS can function autonomously, semi-autonomously with man-in-the-loop lock-on of the automatic tracked or under full manual control. This is the same set of guidance options as the FOG-M.