# Sanity check for earth launched moon pod

1. Jan 28, 2012

### sammorgan101

Hi I've been scratching my head late into the night, and come up with some ideas for a moon pod, I could use a sanity check on the maths and basic idea. Very interested to hear feedback. Post comments here or on my blog...

http://wellybob.blogspot.com/2012/01/travel-to-moon.html

2. Jan 28, 2012

### DaveC426913

Your factual numbers are off by an order of magnitude. I assume "M" is metres.
Distance to Moon is 360,000,000 metres, not 36000000M. Radius of Earth is 6,353,000 metres not 635300M.

The speed at Earth's surface is 447m/s, not 46m/s.

Earth's escape velocity is 11,200m/s - a little higher than the 49m/s you calculated you'd achieve.

And you've done all this to gain a 6% increase in velocity - from 46m/s to 49m/s. Is it worth it?

Finally, what you're making is a junior version of a space elevator without the top half. Considering your tower would have to be 35,000 km tall to have its top achieve orbit, it will have to be even more ridiculously tall to gain enough speed to break orbit to go the Moon.

Seriously, look up space elevators.

But other than that, it looks great! Where do I book!

Last edited: Jan 28, 2012
3. Jan 28, 2012

### sammorgan101

Thanks for the corrections, was done after a few whiskeys last night. Yes I saw the space elevator a while ago, very interesting, this was more a thought experiment in propulsion. Is the escape velocity that you quote from the surface? That's the next bit I need to look into.

Thanks Dave

4. Jan 28, 2012

### DaveC426913

It is, and yes the escape velocity drops with altitude but the problem is that, with your method, you don't each reach geosync orbit without a tower that is 35,000 km tall, let alone escape velocity.

It is physically impossible to build a tower that tall. Thus, the space elevator.