4 ms·

There is some truth to this account: https://books.google.co.uk/books?id=6t-wCwAAQBAJ&pg=PA131&lpg=PA131 https://books.google.co.uk/books?id=6t-wCwAAQBAJ&pg=PA1

There is some truth to this account: https://books.google.co.uk/books?id=6t-wCwAAQBAJ&pg=PA131&lpg=PA131 https://books.google.co.uk/books?id=6t-wCwAAQBAJ&pg=PA131&lp... It's called CORRTEX. And I think you could probably set up a PDP-11 to sample roughly every millisecond so this could work.

walshemj 6y ago
The smaller PDP systems 11/03's where often used in Labs - DEC did a Realtime operating system RT11 for this use case and there where some exotic expansion cards for experimental use. Back in my first job we had a custom built 12 bit ADC used for analysing mixing about £3k per channel in early 1980's £
beamatronic 6y ago
That doesn’t seem fast enough to be useful...
- hwillis 6y ago
  The initial fireball of a nuke is caused by xrays absorbed by air and develops in microseconds. Basically all at once, since the xrays move at the speed of light. A spherical region of air just ionizes. The expanding fireball moves quite a bit slower and increases 10s of meters (from an initial ~10-100 m) over several milliseconds[1]. After that it slows down even more, and if you measure every millisecond you'll see the fireball expanding by meters. [1]: https://pbs.twimg.com/media/Dbf8IK9V0AA38po.jpg https://pbs.twimg.com/media/Dbf8IK9V0AA38po.jpg
  - Tehchops 6y ago
    This phenomenon is referred to as a "double flash": http://wordpress.mrreid.org/2015/04/18/the-nuclear-double-flash/ http://wordpress.mrreid.org/2015/04/18/the-nuclear-double-fl...
- barbegal 6y ago
  A DEQNA ethernet controller card can measure to an accuracy of 100ns which is around 20m at the speed of light. Shockwave velocities in the ground are in the order of 1000 to 10000 m/s or 1 to 10 m/ms so sampling at 1ms intervals should be precise enough. In fact here is a graph produced by CORRTEX https://digital.library.unt.edu/ark:/67531/metadc1200655/m1/6/ https://digital.library.unt.edu/ark:/67531/metadc1200655/m1/... which shows a velocity of ~3 m/ms or 3000 m/s. The sepcialised equipment has much better resolution and samples much faster than every millisecond.
acqq 6y ago
And we have now the easily accessible documents that describe the context: Statement by Deputy Press Secretary Roussel on the Soviet Nuclear Test Ban Proposal, March 29, 1986 https://www.reaganlibrary.gov/research/speeches/32986b https://www.reaganlibrary.gov/research/speeches/32986b "In this initiative the President invited Mr. Gorbachev to send Soviet experts to the United States to examine our new CORRTEX verification system and to observe a U.S. nuclear test in mid-April at our Nevada test site. The President made it clear that if this meeting leads to an agreement on verification -- incorporating CORRTEX -- which meets our concerns, he is prepared to move forward toward ratification of these two treaties." White House Statement on the Soviet-United States Nuclear Testing Talks, December 15, 1988 https://www.reaganlibrary.gov/research/speeches/121588c https://www.reaganlibrary.gov/research/speeches/121588c "Under the terms of a U.S.-Soviet agreement negotiated in the previous round of the NTT and signed at the Moscow summit, underground nuclear explosions were conducted at the U.S. test site in Nevada in August and at the Soviet test site at Semipalatinsk in September, with observers from both sides present. The purpose of the JVE was to allow each side to demonstrate its preferred verification method for the TTBT and PNET. The results of the test were discussed during this round. We believe the experiments demonstrated the effectiveness and nonintrusive nature of CORRTEX, our preferred method of on-site measurement."
kens 6y ago
"CORRTEX" is the magic word for finding details; thank you for that reply. (CORRTEX = COntinuous Reflectometry for Radius vs Time EXperiment.) I found an article explaining CORRTEX at https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-80-3382 https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lar... It's based on a portable Motorola 6800 microprocessor, so the PDP-11 connection is unclear. A coaxial cable is placed up to the detonation point, and as the shock front progresses the cable is crushed, reflecting the TDR pulse back from that point. They call it "Radar on a wire". The interval between pulses is between 20 and 90 microseconds, so this is much faster than the alleged PDP-11 network card. The original system was developed in 1975 and evolved to the 6800-based system. More information in the paper http://dx.doi.org/10.1063/1.1136283 http://dx.doi.org/10.1063/1.1136283
- kens 6y ago
  An earlier system was SLIFER (Shorted Location Indicator by Frequency of Electrical Resonance). It used the same idea of a coaxial cable progressively shorted by the blast wave. However, instead of using reflectometry, it used a resonant Colpitts oscillator whose frequency was 1/4 wavelength. So as the cable was crushed, the frequency increased. Plotting the frequency vs time showed the progression of the blast wave. The oscillator itself was a small circuit board in the blast hole, while data was recorded in a separate trailer. To quote the paper: "In the event the recording facility must be located near surface zero, shock mitigation may be required to assure survival of equipment." The paper includes PCB layouts in case you want to make your own SLIFER system :-) Thanks to kps for the SLIFER link: https://www.osti.gov/biblio/7352892 https://www.osti.gov/biblio/7352892

walshemj 6y ago

The smaller PDP systems 11/03's where often used in Labs - DEC did a Realtime operating system RT11 for this use case and there where some exotic expansion cards for experimental use. Back in my first job we had a custom built 12 bit ADC used for analysing mixing about £3k per channel in early 1980's £

beamatronic 6y ago

That doesn’t seem fast enough to be useful...

hwillis 6y ago
The initial fireball of a nuke is caused by xrays absorbed by air and develops in microseconds. Basically all at once, since the xrays move at the speed of light. A spherical region of air just ionizes. The expanding fireball moves quite a bit slower and increases 10s of meters (from an initial ~10-100 m) over several milliseconds[1]. After that it slows down even more, and if you measure every millisecond you'll see the fireball expanding by meters. [1]: https://pbs.twimg.com/media/Dbf8IK9V0AA38po.jpg https://pbs.twimg.com/media/Dbf8IK9V0AA38po.jpg
- Tehchops 6y ago
  This phenomenon is referred to as a "double flash": http://wordpress.mrreid.org/2015/04/18/the-nuclear-double-flash/ http://wordpress.mrreid.org/2015/04/18/the-nuclear-double-fl...
barbegal 6y ago
A DEQNA ethernet controller card can measure to an accuracy of 100ns which is around 20m at the speed of light. Shockwave velocities in the ground are in the order of 1000 to 10000 m/s or 1 to 10 m/ms so sampling at 1ms intervals should be precise enough. In fact here is a graph produced by CORRTEX https://digital.library.unt.edu/ark:/67531/metadc1200655/m1/6/ https://digital.library.unt.edu/ark:/67531/metadc1200655/m1/... which shows a velocity of ~3 m/ms or 3000 m/s. The sepcialised equipment has much better resolution and samples much faster than every millisecond.

acqq 6y ago

And we have now the easily accessible documents that describe the context: Statement by Deputy Press Secretary Roussel on the Soviet Nuclear Test Ban Proposal, March 29, 1986 https://www.reaganlibrary.gov/research/speeches/32986b https://www.reaganlibrary.gov/research/speeches/32986b "In this initiative the President invited Mr. Gorbachev to send Soviet experts to the United States to examine our new CORRTEX verification system and to observe a U.S. nuclear test in mid-April at our Nevada test site. The President made it clear that if this meeting leads to an agreement on verification -- incorporating CORRTEX -- which meets our concerns, he is prepared to move forward toward ratification of these two treaties." White House Statement on the Soviet-United States Nuclear Testing Talks, December 15, 1988 https://www.reaganlibrary.gov/research/speeches/121588c https://www.reaganlibrary.gov/research/speeches/121588c "Under the terms of a U.S.-Soviet agreement negotiated in the previous round of the NTT and signed at the Moscow summit, underground nuclear explosions were conducted at the U.S. test site in Nevada in August and at the Soviet test site at Semipalatinsk in September, with observers from both sides present. The purpose of the JVE was to allow each side to demonstrate its preferred verification method for the TTBT and PNET. The results of the test were discussed during this round. We believe the experiments demonstrated the effectiveness and nonintrusive nature of CORRTEX, our preferred method of on-site measurement."

kens 6y ago

"CORRTEX" is the magic word for finding details; thank you for that reply. (CORRTEX = COntinuous Reflectometry for Radius vs Time EXperiment.) I found an article explaining CORRTEX at https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-80-3382 https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lar... It's based on a portable Motorola 6800 microprocessor, so the PDP-11 connection is unclear. A coaxial cable is placed up to the detonation point, and as the shock front progresses the cable is crushed, reflecting the TDR pulse back from that point. They call it "Radar on a wire". The interval between pulses is between 20 and 90 microseconds, so this is much faster than the alleged PDP-11 network card. The original system was developed in 1975 and evolved to the 6800-based system. More information in the paper http://dx.doi.org/10.1063/1.1136283 http://dx.doi.org/10.1063/1.1136283

kens 6y ago
An earlier system was SLIFER (Shorted Location Indicator by Frequency of Electrical Resonance). It used the same idea of a coaxial cable progressively shorted by the blast wave. However, instead of using reflectometry, it used a resonant Colpitts oscillator whose frequency was 1/4 wavelength. So as the cable was crushed, the frequency increased. Plotting the frequency vs time showed the progression of the blast wave. The oscillator itself was a small circuit board in the blast hole, while data was recorded in a separate trailer. To quote the paper: "In the event the recording facility must be located near surface zero, shock mitigation may be required to assure survival of equipment." The paper includes PCB layouts in case you want to make your own SLIFER system :-) Thanks to kps for the SLIFER link: https://www.osti.gov/biblio/7352892 https://www.osti.gov/biblio/7352892