[AR] Re: Circa 1968 video about NERVA nuclear rocket program
- From: "Troy Prideaux" <troy@xxxxxxxxxxxxxxxxxxxxx>
- To: <arocket@xxxxxxxxxxxxx>
- Date: Tue, 17 Apr 2018 09:44:51 +1000
On Mon, 16 Apr 2018, Troy Prideaux wrote:
In fact, conveniently, rocket efficiency is often somewhere in the
neighborhood of 50%, so Ve*T is a plausible first guess...
Where is that 50% efficiency number coming from? A mid point between
typical sea level and vacuum ops? If you look at the SSME for example,
its efficiency would be over 70% in vacuum ops.
First, note the phrase "somewhere in the neighborhood of". That doesn't
mean 50 +/- 1, and it isn't the same for all engines.
Well, I suppose it depend on how loose your concept of a ' neighbourhood' is
:)
Elon claims that the Merlin 1D Vacuum engine will deliver 348s Isp in vac
conditions (don't know if that's theoretical or delivered??). To get that
much performance from LOX/RP1 it has to be richer than stoichiometric which
would likely translate to an efficiency of >80%.
Troy
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