PV Gap

Lonnie Said:

whats a cool and different solar system school project for a 4th grader?

We Answered:

The easiest way for a spaceship to get from Earth to Mars, and back again. Werner von Braun developed this in the late 1940s with Willy Ley, they published their work in 1952, and they published a "scaled down" proposal in 1956.

Start from the Earth orbit when it is on one side of the Sun, and curve around so that it intercepts the Mars orbit on the other side of the Sun. It has to be carefully timed so that Mars will be in that spot when you get there, or you're in big trouble!

When coming home, do the same thing in reverse. This is the most efficient way to get to Mars and back. The spaceship uses gravity and centrifugal force to do most of the work. On the way back, the ship can either go directly to Earth, or curve inward to do a "fly-by" on Venus and use its gravity to "slingshot" the ship back to Earth. Again, it has to be timed perfectly so that Venus and Earth are in the right positions when you get there.

If it isn't done this way, the spaceship burns a lot more fuel. And since there aren't any gas stations out there, you have to carry it all with you from Earth when you leave.

This first two links below are charts that illustrate what I'm talking about. (The second one shows the Venus fly-by.) The other two links describe von Braun's two books on the subject.

Kevin Said:

Where can I buy an HVAC Solar System to cool my house ?

We Answered:

I wish I knew this one!