Beyond GPS for JDAM

The Joint Direct Attack Munition, the GPS/Inertial guidance kit that transforms a dumb bomb into a smart bomb has been a smashing success. And it is only one of many GPS guided weapons in the inventory today. The problem is, GPS guidance relies on an external source of information, that is, the constellation of GPS satellites.  GPS is jam-resistant, but not jam proof. Since the early days of the GPS program, the fear has been that sooner or later, someone would be able to consistently jam the signal. 

Not surprisingly, DARPA, the Defense Advanced Research Projects Agency, would like to develop an alternative to the reliance on GPS that current technology provides

I’m not exactly bright enough to delve into the technical aspects of “Chip-Scale Combinatorial Atomic Navigator (C-SCAN)” but I do understand the basics of inertial navigation. Originally using gyroscopes and precession to measure the movement of a platform, most Inertial Navigation Systems today use ring-laser gyros today that use doppler shift in the laser light to measure displacement. And if you know how much a platform is displaced from its starting point, that is, the sum of all accelerations (and decelerations, which are just accelerations in a different direction), you can compute the current location (and velocity) of the platform. 

But INS systems tend to have significant drift errors accumulating over time. Today, most INS systems update from time to time with GPS. That means that even if the GPS is unavailable, the INS platform provides at least some level of navigation capability.  For instance, the JDAM is always labeled as GPS guided, but in actuality, it has an INS guidance system with GPS updates.

If DARPA can work with industry to build a small, reliable system that is completely free of external input, the potential vulnerability of our current generation of GPS assisted weapons would be erased. Other applications on the battlefield, such as Blue Force Tracker systems would also be enhanced.

8 thoughts on “Beyond GPS for JDAM”

    1. I don’t know what’s up with that. Last I heard, it was paid through July. Also ATAC had said they would ensure there was an archive somewhere.

    2. Thanks, man. Maybe just a glitch. Came across via CDR M, at Ace’s place, had about two months with him. Have been going through the archive, digging deep. Quite a loss. 19K, 1st ID, Clinton era. Props to a TC.

    3. There’s speculation over at the facebook group (and I’m sure eventually at the Lexicans) about what’s going on. We’ll see. I hope.

      And technically, despite my online moniker, I was a BC rather than a TC. I like to make fun of tankers, but I also remember they were the nice people who brought 1500hp gas turbine heaters/clothes dryers to the field for me.

  1. Any assist on the FB thing? I am missing the search/link, etc. I am on, and that’s my real name. Battery Commander? Bring some pee to bear on the heathen that we may yet fight another day. I was never cold. Had hot water to wash with.

    1. I was a Bradley Commander. I was an 11M. Started out 11B, transitioned a few years later. Just a lowly SGT.

      There’s several Scutt Ruch’s on FB. Does your profile pic have you and a kid standing on a dock?

    2. Nah, should be me by a Jeep, up in CO. Brad Commander. Bravo Zulu. I took the M-1 cause my bro had. He clued me (gave me the ‘gouge) on the heater, etc. He’s an O-5, J-3 Air @ Bagram now.

  2. Sorry for ‘jacking the comments for the mission. It is a damn good post. When I started picking up on displacement/creep in INS, made me think of the #’s posted on the revetments for alignment. Didn’t do that in the -A1. We were always nearly too far from fuel.

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