[AR] Re: Microlaunchers Book
- From: "Troy Prideaux" <GEORDI@xxxxxxxxxxxxxxxx>
- To: <arocket@xxxxxxxxxxxxx>
- Date: Wed, 26 Mar 2014 13:33:10 +1100
I can’t agree that the point of contention is really one relating to the system
of measurement, but hey, the publication isn’t a mathematical reference (is
it?), so it’s a trivial issue IMHO.
Troy
_____
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On
Behalf Of Charles Pooley
Sent: Wednesday, 26 March 2014 1:20 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Microlaunchers Book
For me, the difference is that the European style of Isp is N-sec/kg and not
Kg-s/Kg and the US practice is pound-sec/pound, not
poundal-sec/pound.
With the European style the result comes out as a number equal to velocity in
meters/sec. If they used the US standard, Isp would be velocity/g.
If g is 9.82, an exhaust velocity of 982 m/sec would be 100 in the US style Isp
and 982 in the European style--982 N-sec/kg.
_____
From: Ed LeBouthillier <codemonky@xxxxxxxxxxxxx>
To: arocket@xxxxxxxxxxxxx
Sent: Tuesday, March 25, 2014 6:50 PM
Subject: [AR] Re: Microlaunchers Book
Troy Prideaux said:
>
My understanding is that convention generally relates c to effective exhaust
velocity and Ve to exhaust velocity so c will only equal Ve if Pe = Pa
You know, I think that the bigger issue is the discontinuity between the metric
system and the US Standard measurement system.
Historically, Isp has always been defined in units of seconds and not in units
of meters/second. Originally, the whole book was
written in the US Standard measurement system. Charles said that he was fine
with doing that. He and I are always kidding
each other about what he calls “that outdated measurement system” (i.e. the US
Standard measurement system) and the
metric system (which I call that “great French attempt at global imperialism”).
...
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