Thats the test pilot standing to the right. That's the open cockpit version the passengers are getting into. The second one, with encosed cockpit never flew. The Entente gave them the engines but forbade flights deeming the aircraft to be aggressive and used for bombing. The use of metal arose...
If you mean the HWK 109-500A-1 (Walter Ri-202) rocked-assisted take off (RATO ) units .. they were working 30s and then were jettisoned to fall the ground by parachute. The accelerator was also called Rauchgerät .