BPJ Code

Synchronous orbits have a period equal to the rotation period of the body being orbited. Watch out for bodies with very slow or very fast rotation periods; the calculated synchronous orbits may be outside the body's sphere of influence, or below the body's surface, respectively - both being nonsense!

Synchronous orbit has semimajor axis blahkm, or blahkm above the surface if the orbit is circular.
The Tsiolkovsky rocket equation relates a rocket's mass fraction and its specific impulse to the mission delta-v it can achieve. For comparison, the Space Shuttle Main Engines (SSME) achieve ve of about 4400m/s in vacuum.

Delta-v available is blahm/s.
Calculate the Schwarzschild radius of a mass in order to determine how closely you can safely approach a black hole. Note that this level of safety guarantees only that you stay within the universe; your comfort may not be what you expect from a top-tier airline.

Schwarzschild radius is at blahkm. Average density is blahg/cm3.
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