Talk:Lippisch DM-1

Influence on XP-92, etc.

Von Karman, who oversaw the investigation of Lippisch laboratory, writes about the impact of his work. The theory of the delta wing was already on people's mind, from the work that Robert Jones did at Langley, and von Karman himself did some supersonic wind tunnel studies on swept wings shortly before the end of the war. But it was controversial. When they found the experiments and interviewed famous aerodynamics people in Germany, it had a stunning impact, instantly confirmed Jones' ideas and ended the debate about swept wings.

Convair engineers Adolph Burstein and Bill Chana have both independently stated that they started with a 45-degree swept wing, and when wind tunnel experiments showed it was unstable, they began increasing the sweep angle and eventually filling it in to be a triangle wing. Burstein claims that Lippisch's work was "moral support" for those advocating the delta wing, but they disagreed with his thick-wing design.

So there is no doubt that Lippisch deserves the honors for being the first to apply delta wing design, and he was consulted by convair. What is incorrect in this article is the claim that the DM-1 glider itself influenced designs. Lippisch's theory was influential, but not the DM-1, which didn't behave well in Langley's supersonic wind tunnel. It was not an ancestral aircraft to the delta-wing fighters. DonPMitchell (talk) 00:43, 4 April 2014 (UTC)

And another point, when Von Karman wrote about the importance of German research on delta wings, he was not referring to the DM-1, he was referring to the supersonic wind tunnel studies done at the secret aerodynamics lab in Braunschweig. The DM-1 was finished after the end of the war and only tested at low speeds (45 mph) at Langley. There was no useful data from it that could influence supersonic fighter design. DonPMitchell (talk) 00:01, 10 April 2014 (UTC)

I have added some comment along these lines, cited from a Smithsonian note. The thin high-speed delta was studied in the USA in parallel with, and independently from, Lippisch's work, and it behaves very differently from the thick, blunt-fronted wing which Lippisch adopted for all his "Nurflügels". The only NACA result which might have interested Convair would have been when NACA stuck a strip on the inner leading edge to simulate a sharp edge, and thus generated significant lifting vortices. The NASM guys admit that there is no direct confirmation of any influence, yet they still insist there "must have been" because meetings took place. The possibility that the meetings might have proved negative does not seem to have occurred to them. Pretty slipshod for a self-styled World Authority, if you ask me. (FWIW the Convair deltas still behaved badly until somebody rediscovered conical leading-edge droop, which Dunne had used on his swept wings of 1907-1913 and Lippisch knew of but studiously avoided. Moreover Dunne discovered the Rogallo-type conical-delta wing in 1904 and included it in his key UK patent of 1909; in truth, the Convair deltas owe more to his lineage than to Lippisch. — Cheers, Steelpillow (Talk) 12:45, 26 September 2020 (UTC)

[Update] A detailed and well-referenced account by Hallion in Aerospace Historian hammers further nails into the coffin of Convair influence. I have edited the article accordingly. — Cheers, Steelpillow (Talk) 03:16, 28 September 2020 (UTC)

Type designation and article title

This aircraft is almost universally known as the Lippisch DM-1 (with hyphen). Sharp (Luftwaffe: Secret Jets of the Third Reich, Mortons, 2015, p.119.) quotes Lippisch as writing it "DM-1", which is significant as Sharp refers entirely to original sources and elsewhere Lippisch invariably used a dot, as in P.13a. Of course, NACA authors later used a variety of punctuations, as NACA authors always do. Thus, both historical correctness and our policy on WP:COMMONNAMES appear to agree that the article title should be Lippisch DM-1. Unless anybody comes up with strong evidence to the contrary, I shall get the move done. — Cheers, Steelpillow (Talk) 12:53, 26 September 2020 (UTC)

First flight

Hello All - On the matter of whether the DM-1 ever flew or not; it seems that it didn't. Past iterations of the Wikipedia page give differing views on this, with the Inbox giving a year for the first flight, even though the article's text states that it was "never flown". The view that it flew in 1944 may have arisen from a misreading of text within Luftwaffe: Secret Jets Of The Third Reich, where on page 116, there are these two snippets of text:

* "Lippisch carried out wind tunnel tests of a simplified P12/13a model, with both fin/ cockpit layouts, before successfully flight testing it in small fin form at Spitzerberg airfield near Vienna in May 1944."

* "Lippisch’s book Ein Dreieck Fliegt, published in 1976, the year of his death, outlines the development of the P12/13 up to the point of the Spitzerberg free flight tests and then sums up the project by saying: “Wind tunnel and free flight tests did not show any particularly difficult handling characteristics, so you probably could go ahead to build a flyable and manned model of this design.”"

Even though the DM-1 could be viewed as a scale model of the P.12/13a, it's not the same device as that flown at Spitzerberg and referred to in the Luftwaffe: Secret Jets Of The Third Reich publication. I've deleted out references to the first flight where apt, and amended the text at the start of the "Development" section, to clarify that the scale model which was successfully flown was related to the P.12/13a project, just so that it's not conflated with the DM-1 project. Cheers, Aerohydro (talk) 08:12, 26 June 2022 (UTC)

Thanks. However the dissociation of the P.12/13 from the DM-1 is not correct. In his Errinerungen (Memoirs) Lippisch confirms that the DM-1 never flew: "Die erste Ausführung der P-13 „Delta-VIP' als Jäger P-13a (Ram-Jet) bzw. P-13b (Feststoff-Rakete), wurde nach erfolgreichen Untersuchungen Im Windkanal den Flugtechnischen Fachgruppen Darmstadt und München (DM) übergeben. Die Konstruktionsarbeiten als Segler begannen im November 1944 in Prien. Für Flugversuche sollte die DM-1 auf einer Siebel-204 hochgetragen werden. Nach Einmarsch der Amerikaner wurde die DM-1 auf deren Wunsch fertiggestellt. Sie sollte mit einer DC-3 Im Mistelschlepp hochgeschleppt und in 5 bis 6 km Höhe gestartet werden. Eine DC-3 stand bereits In Prien und hatte alle Anbauten erhalten, doch wurde im letzten Augenblick die DM-1 In Kisten verpackt und nach USA gebracht." (Trans: "The first version of the P-13 "Delta-VIP" as the P-13a (ram jet) or P-13b (solid rocket) fighter was handed over to the aeronautical technical groups in Darmstadt and Munich (DM) after successful tests in the wind tunnel. Construction work as a glider began in November 1944 in Prien. For flight tests, the DM-1 would have been taken up by a Siebel-204. After the Americans invaded, the DM-1 was completed at their request. It was to be towed up with a DC-3 and launched at an altitude of 5 to 6 km. A DC-3 was already in Prien and had received all the attachments, but at the last moment the DM-1 was packed in crates and taken to the USA.") He also states that the DM-1 was the P.13a design in glider form. However by the time he gave the DM-1 design to the DM students, his aerodynamic ideas were already moving on towards the rather different P.13b. — Cheers, Steelpillow (Talk) 10:02, 26 June 2022 (UTC)

Hello Steelpillow - Thanks for the reply. I probably should have phrased it differently, but I was writing it in a bit of a rush, before having to log-off for the day. Cheers, Aerohydro (talk) 07:11, 27 June 2022 (UTC)