What does a 21st century CAS platform look like?

Has groupthink and possibly a light dusting of intolerance diminished our ability to conceive of ideas other than the accepted wisdom of the time?

Take the discussions around CAS for instance.

To the true believers anything other than the A-10 is heresy; and for them there is plenty of data & evidence that the thing plain & simply does it’s job awesomely.
Others see this period coming to an end, what with MANPADS, highly contested engagement environments and whatever else can be thrown into the discussion.
Too many attempt to shift the discussion towards the latest flavour of the minute.

Whenever people like P.Sprey’s (and others) name is mentioned the discussion becomes so polarised that rational thought, fair contribution and a little creativity become impossible.
We’re better than that, surely?

I keep returning to the words of one of the USAF bigwigs who said that one of the trends they are watching is miniaturisation. Another is the developments in materials engineering.
How would these affect the CAS (and related) missions?

Much of the fighting in the last 20-odd years has been of a boots on the ground sort.
Yes, there is a tremendous amount of lights, colour & sound in the first 5 minutes of the thing, but then it’s back to the hard slog of man-vs-man on the ground.
Always dirty, always slow, and almost never according to some book of rules or doctrines.
Success often determined by improvisation, good logistics, thinking on your feet, and a little help from friends airborne.

People 1st
Strategy & Tactics 2nd
Tools & Toys 3rd

That could be said about WW1, WW2, Korea, Vietnam, Iraq1, Afghanistan, Iraq2, Syria1 …. Syria xxx

But it will be different next time; we are told.
On what basis?

Here are some of my ideas; I doubt they are original so claim them if you will.

Costs and concerns about cost control have always been around; probably always will. Few things are as costly as a war.
Unless you have very deep pockets; the tool must be MUCH, MUCH cheaper than the target. A good ratio here would be: value of tool should be >! (not greater than) 1% of value of target.
For soft target that means a few rounds of ammunition; which means a gun. It isn’t going away.

If these modern PGMs are becoming more accurate (CEPs < 3 metres), then you don’t have to throw a huge weight of them to achieve a desired result.
If you agree to that, then the next step is to question why we need to measure an aircraft’s utility by the mass of ordinance it can carry.
Does the measure of merit become how many times you can attack on a single sortie?

This raises some other questions:

1) These new ultra small precision guided munitions some are small enough to be in the hands of the boot on the ground (thinking of Pike here). Does this reduce the need for CAS?
> Cannot see this for the moment, there’s still a need for a set of eyes on the target from a different angle; possibly a small drone.
Gut feel says we’ll needed someone up there that can take a shot from an angle you cannot. This means a different eyeball close to the action, in contact, with data.

2) Since these new PGMs have become airborne (Pyros, Thales’ FF LMM, SABER), does the need to carry heavy ordinance diminish? Do we need to carry bombs sized Mk81 and bigger?
Then do we still need size XL aircraft to carry them?

3) Much talk about endurance and the only way to get it is to have volume which is the cube of dimensions and therefore only a large aircraft with a large fuel fractional weight will do. Is there no other way?
How about this: the reduction of weight during the loiter part of a mission (usage of fuel) has a few variables and is a function of time, TSFC, L/D.
Easily the most promising one is the L/D; here more is better.
L (lift) = weight of the aircraft.
D (drag) = function of Cd (drag coefficient), velocity (squared) and drag area and a few other bits. This is a rich field for optimisation. Here is where I think we haven’t been too clever.
We spend vast amounts of money to eke a few drag counts out of an aircraft, and staggering $$$ to reduce the weight by a few hairs…and then we go and hang a bunch of aerodynamically dirty things under it’s wings and ruin all that effort.
Almost as if there’s a lack of SYSTEM thinking.
Quite simply clean wings will give a high L/D; therefore internal stores carriage is the way forward.
A good L/D (approaching 15 or 16) in loiter config will allow a much smaller fuel fraction.
A lower velocity, remember it is squared in the drag calculation, will allow a smaller fuel fraction.
And an engine with a lower TSFC, a high BP turbofan, will allow a lower fuel fraction; and a much smaller thermal signature to boot.

So how much stuff needs to be carried?
Here’s my take an a modern CAS platform loadout:
Gun: any modern 25mm that can fire 30 rounds in the 1st second should be OK. Weight ~ 100kg.
Rounds: 20 firing bursts of 30 rounds each = 600 rounds @ ~0.5kg each = 300 kg
Preferably a weapon where the choice of round can be switched between AP & HEI as the situation requires.
I’m thinking a nice long barrelled revolver cannon. (length ~ 70 calibres)

Ordinance:
Only to be used when the gun won’t do.
For softer targets 10 x new miniature PGM. Weight: 10 x 10kg each = 100 kg (Pyros, Pike)
For slightly harder targets; I’m thinking “technicals”: (New Griffin, SABER) ~ 4 x 15kg = 60kg.

To get a really basic estimate of the size of such an aircraft let’s do some sums:
Weight of payload, Wp = 100 + 300 + 100 + 60 = 560 kg
Weight of crew, 100 kg. This is a dangerous job, minimise the risk to 1 man only.

Empty weight of the aircraft is likely to be 55% of the gross weight in this size category. Using the modern materials in ways other than “black metal” might allow even lower. But let’s stick with an Empty Weight fraction of 0.55

The mission:
Warm Up/ Take Off; Climb to 10 km altitude; Cruise at 300Kts for 300 km; Loiter for 4 hrs; 10 x combat runs, (descend, fire/release, climb); return cruise; loiter; descend/land/shut down.
Using a high BP turbofan of TSFC ~42 mg/KN.s (not very good at all) I calculate the required fuel fraction at 0.2725.

As a very rough estimate of Gross Weight: (Payload (560kg) + Crew (100 kg))/(1- Empty weight fraction (0.55) – Fuel fraction (0.27)) = ~2870 kg (5880 lbs in the old language). This thing is tiny.

So, Empty Weight is 2870 x 0.55 =1578kg. Might be too tight…
Fuel Weight: 2870 x 0.27 = 782kg / 0.82 kg/litre fuel density = 953 litres tankage, all internal. (wings and dorsal spine)

Pushing forward a bit.
Using Mattingly’s Master Equation to relate Wing loading to Thrust Loading for just about any conceivable flight condition and converting these to a set of performance constraints; we come to wing loading (W/S) of ~ 240kg/sqm and a Thrust Loading (T/W) of 0.42.
This gives a reference Wing Area (Sref) of ~12 sqm. (little bit more than F-15’s taileron area), with an initial Wing Aspect Ratio (AR) of 6 yields a WingSpan (b) of 8.48 m. Initial taper ratio of 0.5 yields a root chord (Cr) of 1.88m and a tip chord (Ct) of 0.94m. I’m imagining a wing that looks like the A-10 from the front, but with an inner panel with 4 degrees anhedral like the Sukhoi SU-35 planform. Nice for strong vortex lift.

Required SL thrust : ~11.8 kN . To keep costs low, this needs to be an off-the-shelf engine. P&W Canada’s PW530A will do the job nicely.
Engine Dimensions: Length: 1.532m; Fan Diameter: 0.814m; Weight 279.6kg.

Aircraft length: ~9m.

Jeez, I got carried away. Sorry.