Why no tailless delta 'stealth' fighter?

lastdingo

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Has anyone a clue why there's no tailless delta low observable aircraft design?

Think a Mirage 2000 with GE F110 engine, AESA radar, and a bit more blend between wing and fuselage (forward fuselage in typical stealth fighter shape).
The vertical tail would be no issue if the wings are not parallel (hence no 90° angles) and it might even be possible to eliminate it with 3D TVC and as backup split elevons.

The absence of a (second) vertical stabilizer and of horizontal stabilizers should reduce RCS by much.

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I understand deltas bleed a lot of energy in turning, but that could be mitigated with much thrust and doesn't matter all that much when dodging missiles (which is about the most relevant use for agility in the age of 360° lock on after launch WVR missiles). Dodging missiles rather about instantaneous turn rate than sustained turn rate.
A Mirage 2000 was pretty close in agility to a F-16 which had much more thrust, so I suppose deltas don't need to be real bad in ACM (and ACM probably don't matter much any more).
 

overscan

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The straight trailing edge would be bad for stealth. You'd need to sawtooth it somehow. Mirage 2000 intakes would need major redesign.

You'd probably end up with something a bit like the General Dynamics ATF - they were unable to make a workable stealthy vertical tail design and did not finish too highly in the competition.
 

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Dynoman

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There are a few serious designs:
Avenger II was the closest design that I can think of that was a tailless delta. X-47A Unmanned Combat Aircraft design, the original Hopeless Diamond, etc. Straight edges produce radar returns so many designs incorporate leading edge alignment to reduce the different directions in which the returns would be directed towards. Straight edge surfaces are often designed with serrated internal RCS absorbent structures, or exterior serrated designs such as the ones above in the previous post, to attenuate the radar signal.
 

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marauder2048

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I presume the OP means supersonic tailless delta fighters. There's renewed interest in it but it's unclear
if the reduced AoA performance can be compensated for by more energetic munitions which will
tend to chew into the internal payload.
 

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Dynoman

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Even the X-32 had a 'tail' to increase directional control for maneuverability. A true 'fighter' aircraft should have copious amounts of excess thrust, the ability to sustain high-g turn performance, and have slightly negative or relaxed static stability (often compensated for by flight control computers and stability augmentation systems).

In the past aircraft without adequate tail volume and authority would lose directional control while maneuvering. A vertical stabilizer and rudder provides an aircraft with the ability to execute a coordinated turn (i.e. no slipping or skidding). An uncoordinated aircraft will spin if it is stalled (however, its interesting to look at the X-31 tailless program and its Post-stall maneuvering programs). A tailless aircraft typically suffers from lateral instability, loss of directional control at high AoA's, and deep stall characteristics when they depart making recovery difficult.

Therefore, maneuverable fighters typically have large vertical stabilizers to maintain directional control and stability. Tailless configurations maybe more adequately suited to a high speed strike or interdiction aircraft design, or a 'straight-line' interceptor like a MiG-25 Foxbat or a YF-12. However, if you engage in Air Combat Maneuvering, then some form of positive directional control is needed.

NASA and Boeing experimented with the X-36 tailless fighter configuration and found that with thrust vectoring, 'creative' control systems, and tailored aerodynamic design the aircraft could reach good turn performance. However, against a HiMAT type design in an ACM engagement my money would be on the little guy with control surfaces everywhere.
 

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Deltafan

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There was the X-44 Manta program :

https://it.wikipedia.org/wiki/Lockheed_Martin_X-44
 
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