Hum experiencing some unexpected results. I have reworked the engine parameters (the old files will definitely NOT work on the current version of FlightGear). I have also removed all form of SAS so that I can start working in Nasal (to simulate hydraulics ...).
Here are the results. a/ The aircraft flies quite well without SAS . It is less stable, but also more responsive, as could be expected, and there is no longer the "vibrating tail" phenomenon (unlimited speed elevators). Also there is no longer the overresponse in pitch down. b/ You can retain a LOT of aerodynamic control even at 400 000 feet. I expect this to be due to a wrong extrapolation of pressure/density for high altitude, but it is really a nuisance for the X15 since the aircraft went completely ballistic at 200 000ft. 500KIAS at those altitudes is just not convincing. Have to check whether this is really due to the modelling of atmosphere or improper computation of the Airspeed. If it is an issue with atmosphere, would it be a problem if I tried to extend the model to higher altitudes ? c/ Having looked in the source of JSBSIM I read that a rocket connected to only a fuel tank is assumed to be a solid rocket. Annoying if you consider that hydrazine and hydrogen peroxide have been used as liquid monopropellants for restartable rockets (STS OMS and H2O2 RCS on the lunar lander come to my mind)... > Message du 05/01/09 à 01h44 > De : "Jon S. Berndt" <jonsber...@comcast.net> > A : flying.toas...@voila.fr, "'FlightGear developers discussions'" > <flightgear-devel@lists.sourceforge.net> > Copie à : > Objet : RE: [Flightgear-devel] X-15 update > > > Sounds good. However, on the topic of the rockets (and if you are referring > to the existing JSBSim X-15 FDM), I just reworked the rocket engine code > shortly ago. Don't use the external_forces section for rocket control. I've > got tons of information on the X-15, some of which was gained using FOIA > requests. Nowadays, you can simply use the NTRS, like you mentioned. > > Jon > > > > -----Original Message----- > > From: flying.toaster [mailto:flying.toas...@voila.fr] > > Sent: Sunday, January 04, 2009 4:08 PM > > To: flightgear-devel > > Subject: [Flightgear-devel] X-15 update > > > > I have resumed work on the X-15. > > > > I want to model every single thing (from the last bottle of hydrogen > > peroxide to the historical launch sites) for three aircraft > > configuration : > > X15 #1 : Old style flight deck, old style SAS and RAS (later standing > > for Reaction Augmentation System). > > X-15 #2 : X-15A2 configuration with drop tanks and new airframe (the > > one that set the speed record and almost burnt in the process of doing > > so) > > X15 #3 : New style flight deck, Adaptive Flight Control System (a.k.a.: > > MH96), but basic airframe > > > > > > Here are a few hurdles I still have to overcome : > > > > I've got myself a lot of documentation (in part thanks to the Nasa > > Technical Report Server), yet some of the documentation may not be > > available for download (have to collect a list and then see if it can > > be ordered) > > > > Quite interestingly I guess there is some inconsistency in the > > references of the current FDM. Particularly, an article on the MH96 is > > mentionned as the basis of the SAS gains...That would make the current > > FDM representative of the X15 #3 configuration. The thing I am missing > > is that the MH96 apparently used a feedback loop to vary the control > > gain, which I do not find in this FDM. What's more, the MH96 used a > > model of the aircraft in order to impose an artificial behavior (the > > aircraft remained at constant g at low speed without trim for > > instance). The original SAS was much simpler, the pilot choosing the > > gain according to the mission among 12 preset (discrete resistors !) > > values per axis > > > > I think I will have to resort to external forces for all rockets in the > > aircraft (including the main one). Rate of consumption for fuel and > > oxydizer needs to be adjusted according to which tank is tapped by > > which rocket (if you count Ballistic Control System, and the 2 stage > > igniter, there were something like 17 rockets on this aircraft). Some > > of the rockets use monopropellants (H2O2 for the ballistic controls) > > and even more gruesome, the APU is served by the same tanks as the > > reaction control rockets (BCS), and can be crossfed by the main engine > > turbopump supply. > > > > If anybody can give me help in the form of information and/or advice > > > > wish me luck ;) > > > > ____________________________________________________Consultez les > > dernires news dIndochine et coutez leur single Little Dollssur Musiline > > Voila! http://musiline.voila.fr/resume/235 > > > > > > > > ----------------------------------------------------------------------- > > ------- > > _______________________________________________ > > Flightgear-devel mailing list > > Flightgear-devel@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/flightgear-devel > > > ____________________________________________________Des photos de vacances ou des vidéos de réveillons à partager ? 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