Editing V-2 rocket (section)

=== Testing ===
{{See also|List of V-2 test launches}}
{{For|a description of a test explosion|Test Stand VII}}
The first successful test flight was on 3 October 1942, reaching an altitude of {{convert|84.5|km|mi|abbr=off}}.<ref name=Neufeld /> On that day, Walter Dornberger declared in a meeting at Peenemünde:
{{blockquote|This third day of October, 1942, is the first of a new era in transportation, that of space travel...<ref name=Dornberger /><sup>17</sup>}}

[[File:Rocket engine A4 V2.jpg|thumb|right|upright|A sectioned V-2 engine on display at the Deutsches Museum, Munich (2006).]]
Two test launches were recovered by the Allies: [[Sweden during World War II#The Bäckebo rocket|the Bäckebo rocket]], the remnants of which landed in Sweden on 13 June 1944, and one [[Home Army and V1 and V2|recovered by the Polish resistance]] on 30 May 1944<ref># (Polish) Michał Wojewódzki, Akcja V-1, V-2, Warsaw 1984, {{ISBN|83-211-0521-1}}</ref> from the [[Blizna V-2 missile launch site]] and transported to the UK during [[Operation Most III]]. The highest altitude reached during the war was {{convert|174.6|km|mi|abbr=off}} (20 June 1944).<ref name=Neufeld /> Test launches of V-2 rockets were made at Peenemünde, Blizna and [[Tuchola Forest]],<ref name=walter />{{rp|211}} and after the war, at [[Operation Backfire (WWII)|Cuxhaven by the British]], [[White Sands Proving Grounds]] and [[Cape Canaveral]] by the U.S., and [[Kapustin Yar]] by the USSR.

Various design issues were identified and solved during V-2 development and testing:
* To reduce tank pressure and weight, rapid flow turbopumps were used to increase pressure.<ref name=Neufeld />{{Rp|35}}
* A short and lighter [[combustion chamber]] without burn-through was developed by using centrifugal injection nozzles, a mixing compartment, and a converging nozzle to the throat for homogeneous combustion.<ref name=Dornberger />{{Rp|51}}
* Film cooling was used to prevent burn-through at the nozzle throat.<ref name=Dornberger />{{Rp|52}}
* Relay contacts were made more durable to withstand vibration and prevent thrust cut-off just after lift-off.<ref name=Dornberger />{{Rp|52}}
* Ensuring that the fuel pipes had tension-free curves reduced the likelihood of explosions at {{cvt|4000|-|6000|ft|order=flip}}.<ref name=Dornberger />{{Rp|215, 217}}
* Fins were shaped with clearance to prevent damage as the exhaust jet expanded with altitude.<ref name=Dornberger />{{Rp|56, 118}}
* To control trajectory at liftoff and supersonic speeds, heat-resistant graphite vanes were used as rudders in the exhaust jet.<ref name=Dornberger />{{Rp|35, 58}}

==== Air burst problem ====
Through mid-March 1944, only four of the 26 successful Blizna launches had satisfactorily reached the [[Sarnaki]] target area<ref name=Klee>{{cite book |last=Klee |first=Ernst |author2=Merk, Otto |title=The Birth of the Missile: The Secrets of Peenemünde |orig-date=1963 |issue=English translation |year=1965 |publisher=Gerhard Stalling Verlag |location=Hamburg |page=47}}</ref>{{Rp|112, 221–222, 282}} due to in-flight breakup ({{Lang|de|Luftzerleger}}) on re-entry into the atmosphere.<ref name=Johnson>{{cite book |last=Johnson |first=David |title=V-1, V-2: Hitler's Vengeance on London|year=1982 |publisher=Stein and Day |location=New York |page=100 |isbn=978-0-8128-2858-0}}</ref>{{Rp|100}} (As mentioned above, one rocket was collected by the Polish [[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 – {{circa}} May/June, Dornberger and von Braun set up a camp at the centre of the Poland target zone.<ref>Neufeld 1995 pp. 221–222</ref> After moving to the Heidekraut,<ref name=Ordway />{{Rp|172–173}} SS Mortar Battery 500 of the 836th Artillery Battalion (Motorized) was ordered<ref name=Klee />{{Rp|47}} on 30 August<ref name=Pocock>{{cite book |last=Pocock |first=Rowland F. |title=German Guided Missiles of the Second World War |year=1967 |publisher=Arco Publishing Company, Inc |location=New York |pages=51, 52}}</ref> to begin test launches of eighty 'sleeved' rockets.<ref name=Irving />{{Rp|281}} 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.<ref name=Johnson />{{Rp|100}}<ref name=walter />{{rp|188–198}}