Additions and Corrections

• The Atlas is no longer a "missile" but has been converted into a "space launch vehicle".
• The calculation in the Propellant Choice section assumes that there are no losses; i.e., that the "maximum theoretical" Isp will be that which is achieved. There are numerous loss terms not accounted for; hence the flowrate given is incorrect.
• Modern launch vehicles operate fuel rich as stated; however it is not due to a desire to reduce the combustion temperature. Rather, the kinetic losses (losses due to departure from full shifting equilibrium) are a maximum at stoichiometric; the prudent designer therefore selects a mixture ratio "off stoichiometric" in order to minimize the kinetic losses.
• The Test Stand section, asserts that electrical instrumentation wherein a transducer is located on the test stand and an electrical readout is located on the operator's station is too expensive for most amateurs. This is no longer the case. Actuated valves, pressure transducers, etc. and analog-to-digital capture systems for personal computers are very reasonable in price. Furthermore, a computer based system can provide a complete sensor log for the entire run, that will be extremely valuable in diagnosing failure and evaluating performance.
• In the example calculation, I think there may be arithmetic errors in the calculation of the coolant flow gap. Readers are strongly encouraged to redo all calculations for themselves.
• According to John F. Cox <sac10361@saclink.csus.edu>:

  There is a small technical error in the "Heat Transfer" section of the amateur rocket designer's text. At the end of this section the author advises that:

  Material failure is usually caused by either raising the wall temperature on the gas side so as to weaken, melt, or damage the wall material or by raising the wall temperature on the liquid coolant side so as to vaporize the liquid next to the wall. The consequent failure is caused because of the sharp temperature rise in the wall caused by exessive heat transfer to the boiling coolant.

  Boiling is usually a good thing from the standpoint of heat transfer. The author has it right that boiling usually increases the heat transfer. Increased heat transfer, however, results in lowered temperature. Think about that for a minute and it will become obvious.

  The problem with boiling in this application results from something that is called alternately film boiling, jacket boiling, or Liedenfrost boiling. The boiling rate becomes so intense that a layer of vapor is established between the hot wall and the cool liquid. The heat transfer properties of boiling liquid are really wonderful. The heat transfer properties of gaseous vapor really suck. Once the vapor barrier is established, whatever it is that is being cooled will likely melt.

Conversion Factors

Index

Other Notes