June 2020 Dev VersionSome News about the Dev version and what happened on it those last months
Dev version available here:
https://sourceforge.net/p/fgspaceshuttledev/code/ci/development/tree/Easy to install: Download Snapshot, and then specifiy the path in FG Launcher settings
Or the tuto for a proper dev install(easier to update once installed when something is pushed on it)
https://forum.flightgear.org/viewtopic.php?f=87&t=36292Main Changes:
SystemDeep and extensive simulation of Helium MPS Subsystem
10 Helium tanks allowing to pneumatically activate some valves,and to close as a back up hydraulically activated engine main valves,...
Plus the dump of every feedlines going from ET to SSME ( km and km of them and 5 klbs to purge after MECO)
What is truly simulated now is the Helium crossfeed between different engines, in case of leak in one Helium subsytem or engine failure.
Without crossfeed in a defaillant helium system, engine would have been shutdown earlier than expected, to avoid catastrophic explosion within Oxidizer Turbopump ( where LH2 from PreBurner and LOX from Pump would have been in contact without a seal filled with inert Helium).
More infos about that Subsytem there:
https://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-mps.htmlAnd I thrust Thorsten when he said that it was tough to code with all those ramifications


Helium MPS Subsystem switches, right side of the Pilot
Engine ModelSome new things there.
Enhancement in SSME performances regarding several points.
Most important of them are:
- LH2/LOX weights at LiftOff
-Correct mixture ( 6.35 in real, 6.25 in sim)
-Thrust: 470000 pounds for 100% of thrust in Vacuum
-Nozzle ratio for correct Sea Level thrust
Some changes in Launch AutoPilot.
In addition to Apogee, we can now choose a specific flight path angle at MECO ( typically ranged from 0 to 1.2°)
Datas for that are available in SCOM, perfomance section ( part 9)
It allows us to choose the initial orbit shape after MECO ( time to Apogee)
Particularly useful to replicate Real insertion shape and use real values for PEG 4 OMS burn or AOA PEG 4 values available in FDF.
New mission files are already set up with realistic apogee, flight path and MECO altitude targets, and can be of course adjusted at your wishes like before.
Changes in fuel consumption are really interesting.
Even more accurate datas when we compare SCOM and after flight datas with what we have in sim.
Tighter abort boundaries, under a percent of prop remaining at MECO at max load.
We just hit the Final Performance reserve planned by NASA ( less than 1% ie. 8000 lbs ish)
Some interesting graphics to sum up that:
First graphic
Direct insertion in red.
Classic for late STS flight to ISS.
MECO around 350 kfeet, max weight around 40 klbs.
8mn30s for insertion and low on propellant as forecasted at MECO
Purple one is a standard insertion, typical from first missions
More lofted ( MECO at 400 kfeet).
A bit more of propellant remaining in the example ( light payload)
Red curve to be compared with dashed one ( 57° Orbit) below, taken from SCOM performance part section 9
Second graphic
Velocity vs Time
Same as before, red curve reflects a standard launch towards ISS, and to be compared with dashed line from SCOM below:

Quite close, really cool.
Those tiny changes in SSME model have an effect on many other subparts ( like RTLS trajectory, Payload chargeable vs Launch Inclination, etc)
Also more precision in AP for launches close to eastwards ( or westwards) azimuth
An example here, less than 0.05° of Relative Inclination at MECO for Hubble
HubbleReally good work on Hubble and RMS
We can now take Hubble as a payload, grapple it or retrieve it after a sucessful RendezVous.
It opens the path to very interesting Hubble STS mission revivals
DisplaysNot yet on dev branch, but soon.
On my side, in addition of SSME perfos, I wanted some closer to reality PFD.
Lot of minors changed on colors, fonts ( thanks to SSU team for some really nice and accurate shuttle fonts) and overall look.
More details about that there:
https://forum.flightgear.org/viewtopic.php?f=87&t=37429And to come then more enhancements for DPS displays etc now that I know a bit more how to do
