In Roman mytnology, Venus was the goddess of sex. So talking about Venusian entry always makes smile.

Jacob Samorodin appealed to my vanity and asked:

"A question I have on the Venera-3 spacecraft entry into the Venusian atmosphere; I think Gary would have the expertise to answer the question."

I don't know anything about Venera-3 but I know a little bit about Pioneer Venus.

The entry vector for the Pioneer Venus large probe was:

Inertial velocity = 11.538984 km/sec
Inertial entry angle = -32.370586 deg.
Inertial azimuth angle = -124.765303 deg
Altitude at entry = 200.00 km

The peak deceleration for the large probe was 284.69 G.
The peak heating was 4625.34 W/cm^2 [damned hot]

The Pioneer Venus large probe was a successful mission under those entry conditions. So let's play with the numbers. Keep all other conditions the same and vary entry angle:

Entry Angle Peak G Load Peak Heating
deg. W/cm^2
-32.370586 284.69 4625.34
-35.0 305.03 4924.37
-40.0 341.75 5448.10
-45.0 375.63 5941.40
-50.0 405.72 6399.02
-55.0 432.70 6808.24
-60.0 456.49 7167.98

So now we ask. What are maximum reasonable values? The toughest entry in the history of aerospace was the Galileo Probe which entered the atmosphere of Jupiter. It's peaked "blocked" total heat flux was around 15 kilowatts/cm^2. A Pioneer Venus Large Probe with a Galileo Probe heatshield thickness (carbon-phenolic) could easily survive Venusian entry with a 28 deg. miss in entry angle. However the peak deceleration for the Galileo Probe was 207.54 G which is in the same ballpark as the Venus large probe. This makes me suspect that 300 Gs may be near the upper limit for a probe with working electronics.

So now we get back to Venera-3. If the Soviets only wanted to get a nickel coin onto the surface of Venus and they slathered lots of carbon-phenolic on Venera-3's heat shield then they could have hit the atmosphere nilly-willy and probably survived entry. Nickel was a good choice for the coin because nickel won't dissolve in sulfuric acid. I suspect that coin is intact on the Venusian surface and yes, it was a stupid thing to send to Venus.

Gary