Orbital velocity of a craft at 4km above the Moon's surface

  • Thread starter Fred Bobo
  • Start date
What would be the orbital velocity of craft at 4km above moon surface?
Assume a mass of 1,000,000 lb, US.



Science Advisor
For a circular orbit, it's ##\sqrt{\frac{GM}{r}}## where ##G## is the gravitational constant, ##M## is the mass of the body being orbited (here: Moon), and ##r## is the distance from the centre of the body. The mass of the craft doesn't matter.
Find the values on Wikipedia and plug them in. Or, you can make it even easier, and take the escape velocity listed on Wikipedia's page about the Moon, and divide it by ##\sqrt{2}##. The result will be only marginally off.
Thank you.


Science Advisor
You want the one in SI units. Use ##6.674*10^{-11}##. You don't really need more significant numbers as it won't make much of a difference. Then use mass M in kilograms and distance r in metres - again, don't bother with too many significant numbers, unless you really feel like it matters to you if the result is very precise.
Thank you. All good now.
Care: Due to the lunar mascons, low orbits are seriously non-circular, unto 'lumpy'...

Want to reply to this thread?

"Orbital velocity of a craft at 4km above the Moon's surface" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving