Falcon Heavy launches tonight!
The most interesting payload on it (at least for me) is definitely The Planetary Society's LightSail 2. Been looking forward towards this for quite a while as it will be the first controlled spacecraft in Earth's orbit to fly solely on sunlight and hopefully the start of the innovative propulsion technology which has been supported by Carl Sagan back in the 70s already.
Here's some info on how it works:
LightSail 2 is a secondary payload attached to the Falcon Rocket in a small washing machine-sized spacecraft called a Prox-1. Once detached from the Falcon rocket and at a safe distance, Prox-1 will eject LightSail 2 for orbital insertion. On launch, it measures no more than the size of a loaf of bread! Once deployed in space, 4 mini solar panels will open from its sides to power the on-board computers, communications systems, detectors and sail actuators.
The sails themselves are made of Mylar, and at just 4.5 microns thick (one tenth the width of a human hair) are light and reflective enough for sunlight alone to push them into a higher orbit.
Before deployment the entire spacecraft measures just 30 x 10 x 10 cm, while when fully open the sails span an area of 5.6 x 5.6 m or about 32 square metres; and an entire spacecraft weights just 5kg!
A great post with a lot of details can be found here: https://planetarie.wordpress.com/2019/06/24/the-planetary-societys-lightsail-2/