Thanks, that makes sense.
Still not totally clear on how "Dead Mass" and "Liftoff Mass" relate to
stage masses before and after separation. I might claim that "Liftoff
Mass" is something of a misnomer.
Some possible terminology:
- (m_L) Payload mass
- (m_p) Propellant mass
- (m_i) Initial (fueled) mass
- (m_f) Final (burn out) mass
- (m_r) Mass of rocket
These could be further subscripted w/numbers indicating a particular
- m_i1 Mass of 1st stage only, including fuel
- m_f2 Mass of 2nd stage only, excluding fuel
I think maybe (m_1) can be short for (m_i1) etc.
The (m_r) designation always refers to the rocket as a whole:
- m_rb1 Burn out mass of stage 1 + fueled mass of stages 2 & 3
- m_ri2 Initial mass of stages 2 & 3, this would be after stage 1 separation
Even if this isn't the greatest terminology, it's important to specify
which masses are being referred to.
> Total terminology gaffe on my part! "stage seed" refers to the weight
> of the stage above the stage for which we desire fuel numbers. Eg, for
> stage three, the seed should be 1kg, the payload weight. For stage 2,
> the seed should be 4 kg and some change (stage three's wet weight, you
> the stage velocities are as calculated on lines seven and eight of the
> section titled 'iterative approach'.
> I'll clear those details up as soon as I return to a computer!
> On 1/29/11, rq1...@q7.com <rq1...@q7.com> wrote:
> > Looks good!
> > I can't check the iterative output 'cuz the stage speed ("Stage Seed")
> > is missing from the table. (Or i don't understand it, or my browser
> > isn't rendering it, etc.) But if the stage speed was known you could
> > just use the first equation as a simple check.
> > --
> > We should (do?) have a symbols page to define the meaning of these
> > symbols, and/or define them as they are used.
> >> http://psas.pdx.edu/staging/
> > --
> > http://psas.pdx.edu/news/2000-11-02/RA_PSAS_Lecture.PPT
> > http://psas.pdx.edu/RocketSim/
> > http://psas.pdx.edu/2012_liquid_motor_notes/
> > http://psas.pdx.edu/simplerockets_1d/
> > http://psas.pdx.edu/RocketSimPhysics/
> > (2011.01.29) ben...@gmail.com:
> >> I was curious to see what it would take to get a 1 kg payload into orbit,
> >> so
> >> I did some math and wrote some code! Forgive me if this duplicates work
> >> elsewhere on the wiki, but in lieu of a page on "Staging", I created my
> >> own
> >> and populated it to some degree.
> >> Please, kick tires and poke holes! I wrote a small bit of code with the
> >> intention to calculate and iterate fuel needs. I have no idea if it
> >> works,
> >> but simple delta-vee calculations on its outputs are encouraging.
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