![]() ![]() The faster you get up there, the better, as the scramjet accelerates fast but the faster you go, the more fuel it gobbles up at lower (sub-250k ft) altitudes…the fuel flow only starts to taper off close to max altitude. You get circa M10.0 speed and the fuel flow is way lower - I’ve had 26-27,000 lbs/hr a couple times, sometimes seems to be higher, although I don’t know why. It’s a bit game-breaking, but at the moment it seems the most range you can get is at the max altitude, which is 275k ft. The scramjet operation I’ve pretty much figured out, I think. I think there’s a sweet spot between “too agressive” and “too gentle”, which can get you up to 80k ft and M3.0 with almost 3/4 fuel left. ![]() The fuel flow is much less but it takes longer…so not quite sure which one is better. You still nudge the nose down and light the afterburners at 35k, but only tip to 10 degrees down, only descend back down to 25-30k ft and climb at M1.5 or so on a very gentle climb up to 80k-100k before accelerating to M3.0 and lighting the scramjets. The alternative way I’ve been doing it is a gentler, slower climb. ![]() Basically, the fast way to get up to speed is to get to a relatively steep, 20 degree nose down and then start the 1.2G pull up - doing it this way will see the altitude drop to 20k ft before coming back up, but you’ll get past M2.0 which seems to be a bit of a hurdle speed: if you’re doing M2.0+, then the acceleration to M3.0 and the climb up to 80k+ ft takes very little time…however, doing it that way results in very high fuel flow down low. This bit I’m not quite sure about which is the most fuel efficient way. Then it’s time to tip the nose down, light the cans and break the sound barrier. Once levelled out at 30k-35k ft, the dry thrust can accelerate the Darkstar to M0.9, just. Getting to M0.9 in the climb seems to be hard without A/B, so the optimum speed here might be somewhere in the M0.6 - M0.8M range. I’m not sure what the optimum climb speed is, yet - somewhere in the 300 kt - 400 kt range, possibly.Īfter getting out of the thick sea level air, the climb from 15k ft to the supersonic transition altitude is next. I need to do more testing, but it feels more efficient to go on almost a zoom climb after reaching 350kts or so, because the fuel flow at military power drops off rapidly above 10k feet. The first observation is that is correct - it makes little sense to light the afterburners at takeoff - the Darkstar has plenty of power for the takeoff roll and initial climb on dry thrust. Final descent and landing (powered or glide)īasically the main consideration from here is fuel flow on each of the phases - and what you do seems to make a big difference.Turbine engine restart and throttle-up, arrest descent for supersonic cruise phase.Acceleration to minimum scramjet speed (M3.0?).Initial climb (airfield elevation to 30-35k ft).Profile-wise, the flight can be divided as follows: Might be stating the obvious, but it helps me with my ad-hoc analysis. I haven’t ran the numbers yet, but there are a few things I’ll type up. Some of you might recall how in KSP the “space” music starts to play when you escape the atmosphere (70k altitude, from memory)…I was half expecting that music to start playing when I reached 275k ft and chuckled at myself It’s quite fun - reminds me a lot of doing spaceplane things in Kerbal Space Program! About as realistic, also - but who cares! It’s pretty neat to get to do this in the beautiful MSFS world. It’s hard to get a good session in at the moment, but I got to run a few ascent profiles today. Not that we would do that, but it’s good to know.Ī more useful statistic is that 90% RPM maintains a benign 400 kts at the kind of altitudes you may find yourself if looking for an airport after a speed run, and results in a 14 x 1000 PPH fuel flow, i.e. So somewhere between 7 and 12 minutes of full burner at low altitude before flameout. The turbine fuel flow varies quite a bit, but full afterburner at low altitude tops out somewhere around 120-150 x 1000 PPH, less on lower speeds (perhaps 80-100 PPH). It appears that the fuel flow gauge shows turbine FF when the scramjets are off and scramjet FF when the scramjets are on and the turbines off. The middle tanks (marked red below) are the scramjet tanks and the outer tanks (marked blue) are the conventional jet fuel tanks. The scramjet tanks total 21,815 lbs of fuel.Īs far as I can tell, the only fuel gauge in the Darkstar is the visualization of the aircraft with the tanks showing in green. The four conventional tanks total 17,849 lbs of fuel. ![]()
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