Editing Messerschmitt Me 163 Komet (section)

===Later versions===
[[File:Walter HWK 509B-1 USAF.jpg|thumb|A preserved HWK 109-509B "cruiser" twin-chamber rocket motor ([[National Museum of the United States Air Force]])]]
[[File:Me163C 2.JPG|thumb|Model of the Me 163C]]
[[File:Me163D 1.JPG|thumb|Model of the unbuilt Me 163D, erroneously marked with the Me 163B V18's markings for this airframe design]]

The biggest concern about the design was the short flight time, which never met the projections made by Walter. Being capable of a maximum of seven and a half minutes of powered flight - which was only roughly 25% of the 30-minute combat time that the "light-class" [[Heinkel He 162]]A ''Spatz'' single-BMW 003 jet fighter possessed,<ref>Gunston and Wood 1977, pp. 194–195.</ref> when the Komet entered combat in April 1945; the solely rocket-powered Me 163B fighter truly was a dedicated [[point defense]] [[interceptor aircraft|interceptor]]. To improve this, the Walter firm began developing two more advanced versions of the 509A rocket engine, the 509B and C, each with two separate combustion chambers of differing sizes, one above the other, for greater efficiency.<ref name="control panel">Wiedmer, Erwin. [https://www.deutscheluftwaffe.de/Panelnachbau/Erwin/Me163V18Nachbau.htm "Me 163 B V18 control panel"] {{webarchive|url=https://web.archive.org/web/20160410051913/http://www.deutscheluftwaffe.de/Panelnachbau/Erwin/Me163V18Nachbau.htm |date=10 April 2016}}. deutscheluftwaffe.de. Retrieved: 31 August 2011.</ref> The B-version possessed a main combustion chamber—usually termed in German as a ''Hauptofen'' on these dual-chamber subtypes—with an exterior shape much like that on the single chamber 509A version, with the C-version having a forward chamber shape of a more cylindrical nature, designed for a higher top thrust level of some 2,000&nbsp;kg (4,410&nbsp;lb) of thrust, while simultaneously dropping the use of the cubic-shape frame for the forward engine propellant flow/turbopump mechanisms as used by the earlier -A and -B versions.<ref>[http://www.walterwerke.co.uk/walter/me163c1.htm "Me.163B - The Walter RII-211, HWK 109-509.B"]. The Hellmuth Walter Website. Retrieved: 28 July 2013.</ref><ref>[http://www.walterwerke.co.uk/walter/me163c2.htm "Junkers Ju.248 (aka Me.263) The Walter RII-211, HWK 109-509.C"]. The Hellmuth Walter Website. Retrieved: 28 July 2013.</ref> The 509B and 509C rocket motors' main combustion chambers were supported by the thrust tube exactly as the 509A motor's single chamber had been. They were tuned for high power for takeoff and climb. The added, smaller volume lower chamber on the two later models, nicknamed the ''Marschofen'' with approximately {{convert|400|kg|lb|abbr=on}} of thrust at its top performance level, was intended for more efficient, lower power cruise flight. These HWK 109–509B and C motors would improve endurance by as much as 50%. Two 163 Bs, models V6 and V18, were experimentally fitted with the lower-thrust B-version of the new twin-chamber engine (mandating twin combustion chamber pressure gauges on the instrument panel<ref>{{cite web |url = https://www.deutscheluftwaffe.de/Flugzeuge/Projekte/Me163-C/Me%20163C.htm#Risszeichnung |title = Projekt Me 163 "C" - Instrumentbrett der Me 163C mit Marschofen (in German) |first = Erwin |last = Wiedmer |website = deutscheluftwaffe.de |access-date = 3 January 2016 |url-status=dead |archive-url=https://web.archive.org/web/20160125154712/http://www.deutscheluftwaffe.de/Flugzeuge/Projekte/Me163-C/Me%20163C.htm#Risszeichnung |archive-date=25 January 2016}}</ref> of any ''Komet'' equipped with them), a retractable tailwheel, and tested in spring 1944.<ref name="control panel"/><ref>[http://www.walterwerke.co.uk/walter/me163c1a.htm "Me.163B V6 and V18 - The Walter RII-211, HWK 109-509.B"]. The Hellmuth Walter Website. Retrieved: 28 July 2013.</ref>

The main ''Hauptofen'' combustion chamber of the 509B engine used for the B V6 and V18 occupied the same location as the A-series' engine did, with the lower ''Marschofen'' cruise chamber housed within the retractable tailwheel's appropriately widened ventral tail fairing. On 6 July 1944, the Me 163B V18 (VA+SP), like the B V6 basically a standard production Me 163B airframe outfitted with the new, twin-chamber "cruiser" rocket motor with the aforementioned airframe modifications beneath the original rocket motor orifice to accept the extra combustion chamber, set a new unofficial world speed record of {{convert|1130|km/h|mph|0|abbr=on}}, piloted by Heini Dittmar, and landed with almost all of the vertical rudder surface broken away from flutter.<ref name="Käsemann 1999, pp. 17, 122"/><ref>de Bie, Rob. [https://robdebie.home.xs4all.nl/me163/production.htm "Me 163B Komet - Me 163 Production - Me 163B: Werknummern list"]. robdebie.home. Retrieved: 28 July 2013.</ref><ref>[http://www.walterwerke.co.uk/walter/me163c1a.htm "Me 163"]. walterwerke.co.uk. Retrieved: 28 August 2010.</ref> This record was not broken in terms of absolute speed until 6 November 1947 by [[Chuck Yeager]] in [[list of X-1 flights|flight number 58]] that was part of the [[Bell X-1]] test program, with a {{convert|1434|km/h|mph|abbr=on}}, or Mach 1.35 supersonic speed, recorded at an altitude of nearly {{convert|14820|m|ft|abbr=on}}.{{#tag:ref|[[List of X-1 flights]]|group=N}} However, it is unclear if Dittmar's flight achieved sufficient altitude for its speed to be considered supersonic, as the X-1 did.

The X-1 never exceeded Dittmar's speed from a normal runway {{-"}}''scharfer Start''{{-"}} liftoff. Heini Dittmar had reached the {{convert|1130|km/h|mph|0|abbr=on}} performance, after a normal "hot start" ground takeoff, without an air drop from a mother ship. [[Neville Duke]] exceeded Heini Dittmar's record mark roughly {{frac|5|1|2}} years after Yeager's achievement (and some 263&nbsp;km/h short of it) on 31 August 1953 with the [[Hawker Hunter|Hawker Hunter F Mk3]] at a speed of {{convert|1171|km/h|mph|abbr=on}}, after a normal ground start.<ref>Käsemann 1999, pp. 47, 128.</ref>{{#tag:ref|Test Pilot [[Neville Duke]] set a world record on 7 September 1953.|group=N}} Postwar experimental aircraft of the aerodynamic configuration that the Me 163 used, were found to have serious stability problems when entering transonic flight, like the similarly configured, and [[turbojet]] powered, Northrop [[X-4 Bantam]] and [[de Havilland DH 108]],<ref>{{cite book |title = Wings on my Sleeve |last = Brown |first = Eric |author-link = Eric Brown (pilot) |publisher = Weidenfeld & Nicolson |year = 2006 |isbn = 978-0-297-84565-2 |pages = 147 & 184}}</ref> which made the V18's record with the Walter 509B "cruiser" rocket motor more remarkable.

Waldemar Voigt of Messerschmitt's ''Oberammergau'' project and development offices started a redesign of the 163 to incorporate the new twin-chamber Walter rocket engine, as well as fix other problems. The resulting '''Me 163C''' design featured a larger wing through the addition of an insert at the wing root, an extended fuselage with extra tank capacity through the addition of a plug insert behind the wing, a ventral fairing whose aft section possessed a retractable tailwheel design closely resembling that pioneered on the Me 163B V6, and a new pressurized cockpit topped with a bubble canopy for improved visibility, on a fuselage that had dispensed with the earlier B-version's dorsal fairing. The additional tank capacity and cockpit pressurization allowed the maximum altitude to increase to {{convert|15850|m|ft|abbr=on}}, as well as improving powered time to about 12 minutes, almost doubling combat time (from about five minutes to nine). Three '''Me&nbsp;163&nbsp;C-1a''' prototypes were planned, but it appears only one was flown, but without its intended engine.<ref>Green 1970, p. 604.</ref>

By this time the project was moved to Junkers. There, a new design effort under the direction of [[Heinrich Hertel]] at Dessau attempted to improve the ''Komet''. The Hertel team had to compete with the Lippisch team and their Me 163C. Hertel investigated the Me 163 and found it was not well suited for mass production and not optimized as a fighter aircraft, with the most glaring deficiency being the lack of retractable landing gear. To accommodate this, what would eventually become the Me 263 V1 prototype would be fitted with the desired tricycle gear, also accommodating the twin-chamber Walter rocket from the start—later it was assigned to the Ju 248 program.<ref>[http://www.klueser.eu/Me163.php German site about the Me 163]. Retrieved: 5 August 2011</ref><ref>Dressel, Griehl. ''Die deutschen Raketenflugzeuge 1935–1945'' (in German). Augsburg, Germany: Weltbild Verlag, 1995.</ref><ref name = "lepage 249"/>

The resulting ''Junkers Ju 248'' used a three-section fuselage to ease construction. The V1 prototype was completed for testing in August 1944, and was glider-tested behind a [[Junkers Ju 188]]. Some sources state that the Walter 109–509C engine was fitted in September, but it was probably never tested under power. At this point the RLM reassigned the project to Messerschmitt, where it became the [[Messerschmitt Me 263]]. This appears to have been a formality only, with Junkers continuing the work and planning production.<ref>Green 1971, pp. 112–114.</ref> By the time the design was ready to go into production, the plant where it was to be built was overrun by [[Soviet Union|Soviet]] forces. While it did not reach operational status, the work was briefly continued by the [[Soviet Union|Soviet]] [[Mikoyan-Gurevich]] (MiG) design bureau as the [[Mikoyan-Gurevich I-270]].<ref>Green 1971, pp. 150–151.</ref>