Question about Venus probes.

I'm researching our exploration of the planet Venus and there is something that doesn't make sense to me. Considering how hot NASA says Venus is, why didn't the parachutes that the probes used to land burn up when deployed? Thanks in advance.

en.m.wikipedia.org...

a reply to: Aristotelian1

Burning requires oxygen. Not much of that in the Venusian atmosphere.


solarsystem.nasa.gov...

a reply to: Aristotelian1
They wouldn't "burn" so much, but rather just melt. As Phage stated, oxygen is a trace gas on Venus, never found in amounts needed for combustion.

a reply to: Aristotelian1
Those are great answers. Thank you to both of you. The parachutes didn't burn up because there is little oxygen; got it. But this raises a new question. Why didn't the parachutes melt?

a reply to: Aristotelian1

In your research, have you discovered what they were made of? Do you know at what altitude they were deployed and thereafter jettisoned?

originally posted by: Aristotelian1
a reply to: Aristotelian1
Why didn't the parachutes melt?

High temperate material.

Same reason you can put on a set of gloves and pull a 500° pan out of the oven without feeling a thing.

originally posted by: Aristotelian1
I'm researching our exploration of the planet Venus and there is something that doesn't make sense to me. Considering how hot NASA says Venus is, why didn't the parachutes that the probes used to land burn up when deployed? Thanks in advance.

en.m.wikipedia.org...

It appears the only successful Venus landers have been the Russian Venera probes. Here is a Wiki List of Venus missions. A lot of failures, flybys or orbiters but few landers.

Here is a link to the Russian Venera missions with some of the only images of the surface of Venus.
Venera: The Soviet Exploration of Venus

Also keep in mind that Venus' atmosphere is much different than Earth's.

The pressure of Venus' atmosphere at the surface is 90 atmospheres (about the same as the pressure at a depth of 1 km in Earth's oceans). It is composed mostly of carbon dioxide. There are several layers of clouds many kilometers thick composed of sulphuric acid.

nineplanets.org
I don't know how CO2 compares with H2O in regards to free fall speeds but I would imagine it would slow any descent down quite a bit.

Here is more information about Venera 9 lander;

Above the pressure hull was the 2-meter aerodynamic brake, used to slow descent, and the semi-directional helical antenna. Inside the antenna were parachutes and some atmospheric sensors, not intended for long duty on the hot surface... The vehicle landed on shock absorbers and a hollow toroidal crush pad.
...
When deceleration forces reached a predetermined level, parachute deployment began at an altitude of about 65 kilometers. A series of pilot, drogue, braking and main parachutes slowed the vehicle in easy stages, and the two halves of the spherical reentry pod were jettisoned. The vehicle spent about 20 minutes passing through the cloud layer.
Once through the clouds, there was no point in spending unnecessary time in the hot atmosphere. At an altitude of 50 kilometers, the parachutes were jettisoned, and the lander fell for 55 minutes, slowed only by the aerobrake. In the thick atmosphere, terminal velocity was 7 meters/sec at touchdown, equivalent to the impact of being dropped from 10 feet.

Venera9

a reply to: Aristotelian1

For about 30 of the 35 years I worked at NASA as an aerospace engineer I worked in the Space Projects group at NASA Ames Research Center. My office was just down the hall from the Pioneer Venus team which had sent several spacecraft to orbit Venus and put probes into the atmosphere. Although I never worked directly for the Pioneer project, many who did were my friends and colleagues and shared much of their knowledge with me. Over the years, I also worked on a few studies for advanced Venus missions--studying what missions that might follow on to Pioneer might look like.

With that as background, let me comment on your question. The Soviet Venera program (to explore Venus with atmospheric entry probes) was the most extensive Venus program of any nation. The program proceeded in a very logical and systematic manner--starting with small simple probes and eventually going to large complex stations that were able to make it to the surface and interact with it (measuring its load bearing strength, bringing a sample of the surface sand inside the lander, etc). The particular probe that you referenced in the OP was Venera 6--still relatively early in the sequence. It was not intended to nor designed to survive to the surface. According to the Wikipedia article you referenced, it ceased operation about 10 to 12 km above Venus' surface. The Venus atmosphere model shows that the air temperature at that altitude would be about 370 C. At that temperature, in air, Nomex (a temperature resistant Nylon) would start to char. As has been pointed out, Venus' atmosphere doesn't have any free Oxygen, so I would expect that the first thing that would happen to a Nomex parachute at 370 C is that it would lose about 50% of its strength. Since parachutes are usually designed to withstand the peak load associated with initial deployment, loss of even 50% would probably still allow the parachute to function at that temperature for a while.

So, for the particular mission that you referenced (Venera 6) the parachute probably functioned to an altitude well below the design mission altitude (10km). It may even have survived to the surface. However, hot dense CO2 is a very good organic solvent, so I would expect that--over time--the parachute and all its Carbon-containing components would have slowly dissolved into Venus' atmosphere (like an Iron nail dissolving in Sulfuric acid).

Among other things, these early Venus missions measured the temperature and density profile of Venus' atmosphere quite accurately, which enabled later missions to be designed with great precision. Later Venus missions (of both the Soviet Union and the US) were intended to survive to the surface and on the surface for some period of time in order to do useful scientific work. They actually wanted to get down to the surface as quickly as possible and did not use parachutes for the terminal descent phase. (They did use parachutes higher in the atmosphere, however, to extract the descent probe from the entry aeroshell.)