About when did a US/CCCP war become suicidal?

"Tom Adams" wrote
(Peter Stickney) wrote

Size and Weight. Nobody was capable of putting a 30-40 ton warhead of
that size at those heights. Well, that, and atmospheric attenuation -
all the prompt stuff, and the heat, gets absobed pretty quickly by the
Atmosphere,

Less than half the radiant energy of the sun is absorbed.

From Glassstone (10.29), "stopping altitude" is the altitude below which
there is no significant ionizing effect for radiation sourced from above.
From table 10.29, the most penetrating prompt ionizing radiation (gamma and
neutrons) stop at 15 miles altitude.

For the thermal pulse, most of the thermal effects from a thermonuclear
weapon are sourced from X-ray heated air. For an exo-atmospheric detonation,
the thermal source region will be at approximately 270Kfeet altitude
(7.91-92). Again from Glassstone "In fact for bursts at altitudes exceeding
some 330,000 feet (63 minles) the thermal radiation from a nuclear explosion
even in the megaton range is essentially ineffective so far as skin burns,
ignitition etc..."