Re: (Mercury) Atlas Rocket question

Greg Smith

The Internet is your friend.


The main cylindrical portion of the Atlas tanks was alloy 301 stainless steel, 0.040” (just about exactly 1 mm) thick. The taper at the top and boattail at the rear (which also forms part of the engine mount system) were much thicker, between 0.100” and 0.400”.


Compare this to our blast deflector plates, which are alloy 304 stainless (more corrosion resistant but not quite as strong as 301, but from the same general family), 0.125” (11 gauge) thick.


The rule of thumb was that every 0.001” variance in the thickness of the tank walls added or subtracted 100 pounds from the rocket’s total weight, and inversely, 100 miles in range.


The sheet metal used to form the tanks was 36” wide, so there is a welded seam every three feet all the way up and down the missile. That’s one of the other details that makes the Atlas so devilishly hard to model convincingly.


They originally designed the Atlas out of aluminum, but the steel came out about 20% lighter for the same strength. More important, aluminum would lose 85% of its strength at the expected re-entry temperature of 700°F, while the stainless was barely affected at all. Remember that this was an ICBM without a separating warhead, so it had to survive all the way to the target. Purpose-built space boosters don’t have to re-enter gracefully.


The lightweight construction gave the Atlas the highest mass ratio of any rocket in history with the structure being only 2.02% of the liftoff weight. Almost 98% of it was propellants! (This was why the “1-1/2 stage” configuration made sense. Dropping the tanks wouldn’t have saved much mass.)






From: [] On Behalf Of Greg Smith
Sent: Saturday, January 12, 2019 11:07 AM
Subject: Re: [cia-rocketry] (Mercury) Atlas Rocket question


It’s stainless steel plate. Pretty much the same as some of the shiny tank trucks you see on the highway. It’s a VERY difficult finish to duplicate with any kind of paint or foil wrap. A little different color and texture than aluminum.






From: [] On Behalf Of Gary Slater
Sent: Saturday, January 12, 2019 10:23 AM
Subject: [cia-rocketry] (Mercury) Atlas Rocket question


Since we aren't flying today, I am doing other rocket related things today. 


I really feel like I should know this already.  But I don't and I cannot find an answer.

If you know, say so.  I would like to see who knows the answer to my question.

But let's be honest, if you don't know, I would appreciate your honesty in stating so as well.  I hope not to be only one who doesn't know.  


The question:  

What was the skin on the Atlas rockets made of that made them so shiny?  


Thank you, gary.


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