# Slingshot thechnology in space travel

Well, being outside without a pressure suit is a big deal (though still survivable) for a human, but I don’t know enough about time lord physiology to say for them.

And I’m assuming that his superior intelligence is sufficient for making the precise throws that he needs (and ignoring, for the sake of the story, that sufficient intelligence does not necessarily imply sufficient manual dexterity).

These two cases aren’t the same. In fact, they are virtual opposites. First, as a race car driver myself, I’m confident in saying that you can only lose momentum through a turn. You may be thinking about the difference between using the optimum path for a given corner versus a less effective path; a car on the former appears to “slingshot” past the latter.

However, this is not analogous to a satellite’s gravity assist. The corner has no attractive force pulling on the car like the planet. The driver has to brake to reach the optimum corner entry speed. In braking and through the corner, the tires are fighting the car’s inertia, which is trying to push it in a straight line. At (or sometimes before) apex, you apply power to accelerate out of the corner. So the sequence is decelerate/apex/accelerate.

The satellite does not have brakes or an engine, and its sequence is exactly opposite. As it approaches the planet, gravity accelerates it, it reaches perigee, and as it swings past, gravity slows it somewhat, but it has gained speed from the encounter: acclerate/perigee/decelerate.

For years I wondered how gravity assist could possibly work. It seemed to me that the sequence above shouldn’t yield a net increase in speed: why wouldn’t the acceleration on approach exactly balance the deceleration? Finally I realized it was the fact that the planet was moving in its orbit that gave the net gain. :smack:

You are quite right. What is sometimes referred to as the “slingshot” effect in racing cars is actually using slipstreaming to gain a boost in speed to overtake. This has more to do with catapults than slingshots - the suction of the slipstream acting as the rubber band.

Just an irrelevant point of terminology, but I had always understood the leather centrifugal stone-launcher to be just a “sling”, and that the handheld Y-shaped stick with a rubber band between two prongs is a “slingshot”. A “catapult”, meanwhile, is any of a wide variety of low-tech artillery, often involving a long arm with a launcher of some sort at the end, powered by a variety of means including possibly torsion (in which case it’s an onager) or a falling counterweight (in which case it’s a trebuchet).

A “sling” is what you put your arm in when the missile in the hand-held catapult mashed your thumb.