5 ms·

It's really difficult even for seasoned engineers to grasp the scale of difficulty involved. Its rocket science

• InitialLastName 5y ago
  A joke you hear unceasingly when you take tours of engineering schools with a heavy aerospace focus.
  • gerdesj 5y ago
    That's nice but I hope my calcs on the geotechnics of the ground that your school or house is situated on are correct. Obviously, I didn't do the calcs myself and probably no calcs were done at all either. I'm sure everything will be fine. Don't forget the foundations!
• sebazzz 5y ago
  According to Elon it is engineering actually, because science discovers the existing whereby engineering _engineers_ something that isn't now.
• Taniwha 5y ago
  To be fair much of rocket science is essentially extreme plumbing
  • avmich 5y ago
    True :) . Turbopumps are finicky, but at least heat and cryogenics are separated with the turbine shaft. In combustion chambers, you have both mechanical stress from high pressures (and thin walled constructions) and thermal stress - difference of a few thousands K, so chambers aren't that simple either. Still - now we have enough knowledge to repeatedly design flyable rockets from scratch, different teams, periods of time, countries. A lot of work still remains - and the plumbing is a good manifestation for that.
    • jiggawatts 5y ago
      "Separated" The engineering of the seals that can operate at those speeds and pressures is a whole specialised field. If I remember correctly, the SSME design uses a labyrinth seal pressurised with Helium. In other words, the various gases are kept separate only by more gas. Similarly, the Saturn V main engines were unlubricated because no lubricant could be found that could tolerate the extreme conditions. They were just designed to wear out slow enough to keep operating over their operating lifetime, which was measured in hundreds of seconds (including static test firing).
      • throwawaylinux 5y ago
        The turbopumps for the main engines were unlubricated? No fluid bearings? What do today's reusable engines use?
        • jiggawatts 5y ago
          If I remember correctly, on the fuel side they use the fuel itself (kerosene) as a lubricant where possible. On the other side I believe they ran dry, but I'm not an expert in the topic.
          • throwawaylinux 5y ago
            Interesting: https://ntrs.nasa.gov/citations/19950008234 https://ntrs.nasa.gov/citations/19950008234 "Liquid oxygen is [the high pressure oxidizer turbopump's] only lubricant and a poor one at that." So it's some lubricant and I imagine also significantly a coolant. This https://ntrs.nasa.gov/citations/20100023061 https://ntrs.nasa.gov/citations/20100023061 goes into a lot more detail. But exotic materials and designs bathed in LOX which provides cooling (and minimal lubrication) seems to be how the space shuttle engines achieved their long bearing lifetimes.
        • HPsquared 5y ago
          The bearings of something running that fast, under that much stress, would 100% need to be lubricated. Probably the seals are what would have no lubrication and gradually wear out. Look up "labyrinth seal". Edit: They used carbon seals. The turbopump uses ball bearings cooled by the fuel. Detailed description here: http://web.archive.org/web/20150509173846/http://agentdc.uah.edu/homepages/dcfiles/USSRC/F1EngiFamiTraiManu%20Section%201_072308152849.pdf http://web.archive.org/web/20150509173846/http://agentdc.uah...
• kylecordes 5y ago
  As I understand, rocket engineering makes rocket science look pretty simple by comparison!
• simonblack 5y ago
  If you cut open a rocket engine, is it rocket surgery? Does that require even more knowledge?
  • HPsquared 5y ago
    I suppose overhauling a reusable rocket engine would count as surgery.