Mechanical Engineering applied in rockets

[becker]

Hello!

I'm a Mechanical Engineering student and I have a work with my classmate about mechanical engineering applied in rockets, so I wonder what are the best topics to talk about it: projecting the rocket aerodynamics? The rocket engine? History of rockets? We are first working in the abstract, so I need a general idea of this subject (an introduction).

 

Ps: I'm not a lazy guy, I just want to know some opinions of users that know about this subject as an orientation.

 

Thank you very much!

[Enthalpy]

Hi Becker!

 

Rockets need much mechanical engineering, it's just that few people need rockets.

 

And what kind of rockets do you have in mind: for firework, to throw boat ropes, bring combat aircraft down, launch satellites...? Their needs in mechanical engineering differ quite a bit.

 

For satellite launchers:

• The drag coefficient has no importance, except at the very smallest launchers. The fairing's shape shall only minimize vibrations at transonic speed. Minimizing the side lift at the fairing would be nice, since this is a dimensioning stress on launchers, but I fear little can be done.
• Tanks are very much a matter of mass optimization. Special construction was invented for them. Interesting topic. Graphite could be the next step for liquid propellants.
• The engine's chamber walls must be cooled actively if not ablatively. Special manufacturing methods had to be invented.
• The engine's turbopump (if using liquid propellants) is a headache of mechanical engineering. Ball bearings are misused far outside their spec, only propellants can cool the bearings but many are horrible lubricants (oxygen, hydrogen), joints are difficult because of speed, temperature and vacuum. Hydrogen is too light and needs high impeller speed and several stages. Hydrodynamic bearings are to be the next thing.
• A current trend is to 3D-print parts of the engines: the injector, now the chamber walls.
• A rather detailed description of the RD-170, perhaps the most fabulous liquid engine ever developed:
  http://www.lpre.de/energomash/RD-170/index.htm