Project Here goes nothing: The Delta-StarLiner G42

[martins]

Having air inlets on top of the wings seems quite unusual. Could this cause problems with air intake during high AOA maneuvers (in particular given the massive chord length of this plane), even before a stall?

 

[Moach]

well, the Northrop b2 seems to pull off the same upper-wing inlets without much trouble (that i´ve heard of, at least)

but it makes sense that a drop in air pressure caused by high AoA could cause a performance drop.... but well, this thing is not made to go through stalls during powered ops, so i guess if you keep your nose low, there should be no problems...

also, this ship has considerably more lift than the DG, so it´s less likely to need such high AoA for maneuvering

in the up-front shot, you can see how the wings are curved along the leading edge, this, like in the concorde, creates a large vortex above the wing at high AoA, which allows it a slower stall speed


anyways, with the suction from the SABRE engines, the performance drop from a stall could be less than noticeable, at least for the pilot, who will definitely have more urgent matters to worry about :hmm:


as for the engines, right now we have two radial aerospikes instead of linear, looks more delta-glider-ish, but if you guys want i can just as well switch those for a linear model

 

[Bj]

well, the Northrop b2 seems to pull off the same upper-wing inlets without much trouble (that i´ve heard of, at least)

But the B2 has the inlets much closer to the front, meaning a higher AOA would be needed for the airflow to the inlets to be disrupted. Making the inlets farther back might mean that airflow would be disrupted even at minor AOA. Though all hypothetical, you would have to test in a wind tunnel to get real data to make it as realistic as possible.

 

[Urwumpe]

well, the Northrop b2 seems to pull off the same upper-wing inlets without much trouble (that i´ve heard of, at least)

Different flight conditions, the B-2A doesn't reach high AOAs at all and flies always subsonic. As long as the wing doesn't stall in front of the air inlet, the inlet works - at subsonic speeds.

You're flying at supersonic speeds, so the position of the air inlets does matter much more. At very high supersonic speeds, the position is even critical, the whole fuselage of the plane is the inlet. Which is why all SCRamjet prototypes either use annual inlets (cone at the front) or have an rectangular inlet at the bottom of the plane, with a specially curved lower side of the plane.

The inlet is not just "the point where the air goes in", it has more jobs, the term "inlet pressure ratio" is a good hint... the inlets also compress the air initially for having the right conditions for the compressor to work.

but it makes sense that a drop in air pressure caused by high AoA could cause a performance drop.... but well, this thing is not made to go through stalls during powered ops, so i guess if you keep your nose low, there should be no problems...

At supersonic speeds, it is even more extreme. Tiny variations in AOA or sideslip angle can mean a complete inlet stall, which means the airflow inside the inlet reverses direction, air is pulled through the inlet out of the engine. That is why the inlet cones of SR-71 or ReactionEngines Skylon move forward and backward, and why the cones are so exposed compared to the rest of the plane. They need it for positioning the Mach shock waves of the tip of the inlet cone right at the lip of the inlet, so the reflected shock waves compress the air without stalling.

in the up-front shot, you can see how the wings are curved along the leading edge, this, like in the concorde, creates a large vortex above the wing at high AoA, which allows it a slower stall speed

And have the engine awash in the vortex in this case. Bad bad bad idea. also your curve is not strong enough, you wouldn't get a vortex with such a small angle.

anyways, with the suction from the SABRE engines, the performance drop from a stall could be less than noticeable, at least for the pilot, who will definitely have more urgent matters to worry about :hmm:

as for the engines, right now we have two radial aerospikes instead of linear, looks more delta-glider-ish, but if you guys want i can just as well switch those for a linear model

Where are the inlet spikes of the SABRE? Also, suction from an engine works at low mach numbers to supply air, but at supersonic speeds, the air simply doesn't notice that your engine exists.

 

[Linguofreak]

If you're using DeltaGlider-tech rocket engines than all the airbreathing technology is a waste, since the specific impulse of the rockets is greater than that of the scramjets on the DG-S.

If you're going for a more realistic rocket engine, though, some of this exotic air-breathing tech may be worth the extra mass.

Nah. With a realistic rocket engine, a multi-stage-to orbit tower design is much more reasonable than any sort of horizontal-takeoff SSTO.

What you really need is to distribute some of the magic on the DG-S from the rockets to the airbreathers.

Since your engine is presumably nuclear, use the same reactor (or whatever), instead of jet fuel to heat the airstream. You can then tone some of the magic in the rocket phase down (by reducing thrust and/or ISP), and try an integrate your engines, so that instead of having turbos, scrams, and rockets for the three different speed regimes (or, in the case of the DG-S, just scrams and rockets, and having to use rockets at low speeds), you have one engine that works across your entire flight regime in three modes. It also helps if your scram mode has a high cutoff speed, a la the XR1, rather than the DG-S.

 

[Moach]

hmm no... nothing here is "nuclear", i´m not going so sci-fi with this thing... so i guess i should move those inlets to the bottom side... can be done, no problems there

or could them somehow share the inlets for the scramjets, some sort of internal splitter valve? nah... scram inlets are highly specialized, better not mess with them...

let me think of something else...

 

[Urwumpe]

If you have pure SCRAMs, you don't want hybrid rocket engines. That is actually a penalty. Better use rocket engines for launch, so you exceed the critical Mach number quickly, then switch to SCRAMs and power down the rocket engines, and then go back to use rocket engines when the SCRAMs overheat. The SCRAMs can use the air far better as any hybrid rocket engine can, the SABRE is even just a RAMJET/rocket combination, that works at lower Mach numbers.

 

[Ghostrider]

hmm no... nothing here is "nuclear", i´m not going so sci-fi with this thing...

Well, if it contains nuclei, it's nuclear. Sort of.

 

[Moach]

here´s a variant with ram spikes... not sure what i think of it...

another possibility is to add the inlets on the bottom, next to the scram doors


any thoughts?

 

[Andy44]

The problem with having inlet cones like that is that the tips will melt on re-entry. Maybe put the scram inlets somewhere on the belly with retractable heat-shielded doors.

Personally, I liked the look of the dorsal inlets better, maybe there's a way to choose a different engine configuration so that you can keep it...but for realism, engineering beats aesthetics.

 

[Bendarr]

Why is it every time I see that Pic I end up thinking that the main component of the RAM on a B2 is Denim?

Carry on. I was never here. By the way, love the design so far.

 

[Izack]

Why is it every time I see that Pic I end up thinking that the main component of the RAM on a B2 is Denim?

Carry on. I was never here. By the way, love the design so far.

Random comments thread?

 

[cinder1992]

Why is it every time I see that Pic I end up thinking that the main component of the RAM on a B2 is Denim?

Carry on. I was never here. By the way, love the design so far.

Denim is actually brown, not the classic blue that Levi Strauss made his bluejeans with... yes. he DYED them.

 

[Sky Captain]

What kind of fuel this craft is supposed to use? If it`s LH2 there seems to be too little internal volume to carry enough LH2 for reaching orbit even with mostly airbreathing ascent. Or are there planned to be a droptanks to boost the fuel capacity?

 

[Moach]

yeah, fuel´s probably not gonna be anything currently available... it´s a near-future craft, so "some" furutistic stuff is acceptable, as long as it´s simple, like more efficient fuel and lightweight heat-resistant materials...

what i´m trying to avoid is "breakthrough propulsion methods" or "revolutionary, impossible systems" - that would be "cheating"... and i wouldn´t feel good flying a cheat-ship

but that there will be more efficient fuels and materials in the future is pretty plausible, so it´s a fair stretch from present-day tech


conceptually, the SABRE inlets are to be closed when entering SCRAM speed near mach 3~4, and the only moments where the ship is to be flown with high AoA and SABREs running is when it´s subsonic...

so as long as you don´t pull hard up while supersonic (aka: suicide), the engines shouldn´t suffer... it´s just a matter of flying her gently

so i´m thinking of bringing the upper-wing inlets back... there may be a hidden advantage of having them in that position, the air above the wing is at lower pressure, and therefore cooler than the air below

plus - they looked very cool...


mind that those arent EXACTLY SABRE engines, they are near-future variants of them, even lighter and more efficient (not exagerately, tho)

drop-tanks and SRBs are indeed in order for long-hauls, trips to high orbit or the moon, as is the possibility of filling the cargo bay with extra fuel tanks...
this ship should have multiple possible launch configurations, to suit the needs of different missions - including piggyback launch from another craft, or vertical T/O with tanks and solids like the shuttle


so i guess the upper inlets stay, they´re not so unlikely after all...


i´ll have their design re-thought, tho... should be similar, but exactly the same


cheerz

 

[Donamy]

Seeing this vehicle develop, makes me long for the Black Dart.

 

[Urwumpe]

Seeing this vehicle develop, makes me long for the Black Dart.

I know I know I know I know I know I know I know I know I know I know I know I know I know I know I know I know I know I know.

Can I now go into the basement and cry?

(So much to do, and so little time.)

 

[wehaveaproblem]

Hey Moach,

Nice model so far and interesting choices being made, should be a fun bird to fly.

I can take a guesstimate , but what are her dimensions?

 

[Turbinator]

What a beauty.

 

[Moach]

alright, they´re back!

cheerz