Through mid-March 1944, only four of the 26 successful Blizna launches had satisfactorily reached the Sarnaki target area due to in-flight breakup ("Luftzerleger") on re-entry into the atmosphere. (As mentioned above, one rocket was collected by the Home Army, with parts of it transported to London for tests.) Initially, the German developers suspected excessive alcohol tank pressure, but by April 1944, after five months of test firings, the cause was still not determined. Major-General Rossmann, the Army Weapons Office department chief, recommended stationing observers in the target area – May/June, Dornberger and von Braun set up a camp at the centre of the Poland target zone. After moving to the Heidekraut, SS Mortar Battery 500 of the 836th Artillery Battalion (Motorized) was ordered on 30 August to begin test launches of eighty 'sleeved' rockets. Testing confirmed that the so-called 'tin trousers' – a tube designed to strengthen the forward end of the rocket cladding – reduced the likelihood of air bursts.