I was wondering about some of the really early lifting body designs, which weren't so much "lifting bodies" as lifting blunt bodies; shapes like the Ames M-1*, Martin Model 410, Martin W-1, and so on. These were basically flattened/truncated cones. AFAICT, no one ever did a flight test of these shapes (probably because they couldn't be landed conventionally: they were strictly for improved hypersonic L/D), and it's surprisingly hard to find any information about them at all.
Does anyone know of any good sources about these shapes and why all interest in them seems to have vanished by the mid-1960s? Was it because CG offset allowed conventional capsules to get reasonably large hypersonic L/Ds, while the subsonic L/Ds of these lifting blunt bodies meant that they weren't very attractive for post-Apollo systems (like Shuttle)?
* The shape in the middle of this image. The one on the left is the M2-F1, essentially, the one on the right is a lenticular vehicle.
Speaking of lenticular vehicles...
Everyone knows that Joe Engle flew both the Shuttle and the X-15, but has he ever spoken about his one and only tow in the M2-F1? It's listed that he did a ground tow, but I've never been able to ascertain if he got airborne during it.
How was this different from the M2 Lifting bodies shapes? Are we talking a different trunication (on the bottom perhaps) such as the FDL series:http://www.google.com/search?q=FDL+lifting+bodies&hl=en&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=qn_XT73VCI-c8gSd-bG9Aw&ved=0CHUQsAQ&biw=1280&bih=829
A good Google search on the various FDL (Flight Dynamics Laboratory, FYI) lifting body types especially the FDL-5/7 series such as proposed for the "Silver Dart" and the "Hyper-III" turns up a bit. Especially if you hit up the DoD type sites
Isn't that one a more 'oval' shape similar to the proposed "Spacecruiser" type hypersonic lifting body?http://www.dod.mil/pubs/foi/Science_and_Technology/Other/883.pdfhttp://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADB143755http://www.secretprojects.co.uk/forum/index.php?topic=1103.0http://www.dod.mil/pubs/foi/reading_room/883.pdf
IIRC, the primary differences between the M-1 and M-2 had to do with the back end. Reed said (I'm paraphrasing) that they added the boattail, fins, and cockpit/flow fence. These changes were necessary to handle the tendency of the M-1 to become (ahem) rather unstable in the transonic/subsonic regime.
On the shift back from sharp shapes, the more bulbous shapes had a higher volumetric effeciency.
Quote from: GClark on 06/13/2012 01:30 amIIRC, the primary differences between the M-1 and M-2 had to do with the back end. Reed said (I'm paraphrasing) that they added the boattail, fins, and cockpit/flow fence. These changes were necessary to handle the tendency of the M-1 to become (ahem) rather unstable in the transonic/subsonic regime.I can see how that would be a problem for the Dryden people, yes. How much would it have mattered for a reentry vehicle descending on parachutes, which could presumably have deployed a supersonic parachute for stability during the transonic regime, then subsonic parachutes for final deceleration and landing? Wouldn't the parachutes have provided a significant amount of stabilization themselves?
Quote from: GClark on 06/13/2012 01:30 amOn the shift back from sharp shapes, the more bulbous shapes had a higher volumetric effeciency.True, I suppose the performance of the sharp shapes isn't needed for, eg., Dream Catcher or HL-20, since even the bulbous shapes can get acceptable subsonic L/D. I wonder if the Air Force looked at the sharp shapes further for, eg., their sortie vehicle? In that application, the greater hypersonic L/D of the sharp shapes seems like it would be more useful.
Well there is ONE issue right there you know Dryden folks were AIRCRAFT people and it not only had to FLY to a landing it had to MAKE an aircraft type landing. None of this "parachute" stuff going on around here!
Seriously if you look into the work done with the various FDL shapes over the years and what the Air Force was looking at as opposed to what NASA was lookng for you should note that the types of lifting bodies you're talking about WERE what the Air Force prefered. Mostly BECAUSE they had such high hypersonic L/D numbers
BTW, it's "Dream-Chaser" as a "Dream-Catcher" is loop with all sorts of chrotchey strings criss-crossing the middle
Wings are structurally thin airfoils designed specifically to provide lift, with an aspect ratio of 1 or greater. The term "lifting body" has generally been applied to vehicles designed for atmospheric entry with lift greater than that provided by capsules but which did not utilize wings.I clearly recall the llifting body concept presented in a short video in the '60's which said that wings with a sharp leading edge would melt due to entry heating. Quite a range of lifting bodies were tested but it isn't clear that any ever achieved an unpowered landing at a realistic weight for an entry vehicle. With the development of RCC, the carbon composite leading edge material which can tolerate extreme temperatures, the Shuttle program quickly recognized the major improvement in L/D possible with conventional wings and took that path instead.Anyone who has watched the Shuttle land in marginal winds knows how valuable every bit of lift can be on final approach, and how much safer it would be with a lower touchdown speed and greater control margins. I cannot imagine selecting a vehicle with even slimmer safety margins for landing on a runway. Conversely the X-37, which evolved from the Shuttle design, has landed twice from space at a relatively comfortable speed of about 100 knots and with no visible TPS damage at all.Yet I can find no indication in the Commercial Crew selection criteria that any advantage was given to a vehicle with better aerodynamic performance (i.e. the OSC Prometheus). Apparently the Dreamchaser was chosen over the Prometheus because of its larger passenger capacity (4 vs 6, although both met the spec) without any consideration of such basic aerodynamic criteria as lift and drag.
without any consideration of such basic aerodynamic criteria as lift and drag.
https://docs.google.com/viewer?a=v&q=cache:xYntI079RnwJ:ftp://ftp.rta.nato.int/PubFullText/RTO/EN/RTO-EN-AVT-116/EN-AVT-116-02-APP-01.pdf+&hl=en&gl=ca&pid=bl&srcid=ADGEEShvwgZ5Gr06tY4Oz3SV6PLJP7E9LiqdFGBCYyADH93lR7mgkZ5MuszOorjTF5Ush_VYmM3uoWJTgGxOfjGnyR1xwQxESxZsXSA3WQNRKJxNfpBgjMZpa5bHgTPp4H5xWTX9LR6v&sig=AHIEtbTP8XGDvIOG4TM5HHpvqZN_G5y1kw