W H G
  • Member for 1 year, 8 months
  • Last seen this week
Keplers equation: written in change in eccentric anomaly
Accepted answer
5 votes

The Eq. 4.43 is in Battin's An Introduction to the Mathematics and Methods of Astrodynamics where he does not derive it. The derivation is outlined in his earlier book Astronautical Guidance (1964) on ...

View answer
Could someone explain this formula for da/dt?
3 votes

It is one of the Lagrange Planetary Equations. A very similar form is given by Archie E. Roy (The Foundations of Astrodynamics, 1965 at page 175 and Orbital Motion, 1978 at page 184). Be careful in ...

View answer
Hohmann transfer using GMAT software
Accepted answer
2 votes

Assume the velocity increment is at the perigee and along the velocity then the new velocity is $V$, calcualate the semimajor axis from the vis viva equation: $V^2 = \mu (2/r - 1/a)$ The apogee ...

View answer
First cylindrical Earth satellite? Last?
2 votes

First U S satellite Explorer 1, launched February 1, 1958 and reentered in 1970. While the batteries lasted 4 months it was used to discover the Van Allen radiation belts. From Wikipedia:

View answer
Calculating rocket nozzle throat area
2 votes

Probably units and the format of eq (7) are the problem. After looking at the referenced website by Nakka, I used the questions information given to get $\dot m= 1.187 kg/s$ (using a rounded off r=...

View answer
Calculating the time of flight between two anomalies gives a negative result?
Accepted answer
2 votes

When true anomaly is between 0 and $\pi$ the formula for E is fine, but above $\pi$ you have to adjust the Arctan value to get E in the right quadrant. It looks like just add 2$\pi$ to a negative ...

View answer
Would major changes since "Equations of powered rocket ascent and orbit trajectory" was written reduce its applicability?
Accepted answer
2 votes

I would say it is a good reference. It is not a book, but rather a 33 page paper (one page is distribution page so no real information). I got a copy of the pdf from dtic.mil. A quick search shows the ...

View answer
I'm having a problem with the Throat Area formula derivation
2 votes

The equation shows that the cross-sectional area of the nozzle depends on the local pressure $P$ and values that are constant. So, he expects you to differentiate with respect to $P$, set the result ...

View answer
Specific Heat Ratio for a perfect gas mixture
Accepted answer
2 votes

Universal gas constant R' is correct. Sutton uses $C_p$ for molar specific heat and $c_p$ for mass specific heat. See table of symbols at end of chapter (I have the 7th ed.).

View answer
Any star-system list indexed by proximity?
1 votes

Check out http://www.johnstonsarchive.net/astro/nearstar.html which list planets and stars to 25.1 ly but last update in 2018. Also, http://www.johnstonsarchive.net/astro/nearstarmap.html I found this ...

View answer
Trying to make a program to calculate (liquid) engine size. Can you please help me check for any problems?
1 votes

Good thing that you asked for help. As people work in a field, they develop an idea of the magnitude calculated quantities should be. Your exhaust velocity looks reasonable but the propellant flow is ...

View answer
Nozzle throat velocity
1 votes

Signals (like pressure change) can propagate upstream in subsonic flow so the flow ahead of the throat will sense the throat ahead. That is my best explanation. From an equation standpoint I remember ...

View answer