Stratos II+ rocket on the launch pad on Tuesday evening.

A farewell to the rocket

Yesterday evening and this morning were also the moments the team gave a final farewell to the rocket. While we have every intention to recover the Stratos II+, we even have a helicopter on standby, the reality is that recovering a rocket is hard. First we’ll light a 2500 degree Celsius fire in the belly and accelerate it to 3000 km/h after which it’ll fall to the ocean from 50 km altitude. Then it’ll have to float long enough to be found by the helicopter and boats. There is thus a very real chance that the thing that kept this team busy for 4 years will never be seen nor heard of after today. We all hope for the best though.

Launch countdown

The countdown is helped by our software which is monitoring hundreds of parameters on the launch vehicle and the ground system. Part of the launch countdown are two events which will take fairly long: launching the weather balloon and lettings the tank pressurize.

Test of deployment of a weather balloon

The balloon is used to probe atmospheric conditions in the flightpath of the rocket. In this manner we can get a handle on how the winds higher up are, as they potentially cause the rocket to veer off the intended course. As balloons don’t ascend as quick as the rocket and time is needed to process the measurements, the launch countdown is likely to be halted for a while as our range safety officer evaluates the balloon data.

Tank pressurization is done by allowing the nitrous oxide to slowly warm using the Iberian sun and tank heaters attached to the launch tower. Due to the high vapor pressure of nitrous oxide no separate pressurization system is required. The propulsion system of the Stratos II+ is known as a blow down system. As we carry quite a bit of nitrous oxide the process will however take a while to complete.

Wind and direction

It’s not just the wind at high altitude that is of concern, the rocket is pretty picky on surface wind conditions. In order to be able to launch safely, we need a wind speed of about 18 km/h steady from the south. If it is any stronger or from any other direction we can’t fly. This wind requirement stems from the fact that the Stratos II+ is passively stabilized. This means that it will always turn into the air stream. Once the rocket is picking up speed the effective air stream will only be coming from the front as seen from the rocket. At liftoff when the rocket has little speed, the wind however has a fairly large influence on the perceived air stream by the rocket. Wind from the South will ensure that the rocket flies over the Atlantic ocean where it can safely land.

This is the weather we are hoping for!

Watch us live

Follow us on the live stream as we make our way through the dozens of steps on the launch procedure to lift off of the Stratos II+ rocket.