Ducted-Fan Performance

[XLjedi]

What have you been seeing for max sustained cruising speeds on your ducted-fan designs?  (the BG expansion robotics blades)

Granted, I can peak-out in the 290 range for short intervals... but for a sustained cruise I'm maybe seeing something around 275 m/s in the 1000-1500m altitude range?  (Kerbin atmosphere)

Have your observations been any different?

 

 

Edited December 16, 2019 by XLjedi
I mis-quoted turbo-fan when I meant ducted-fan

[VoidSquid]

New 1.8.1 career, with the J-33 "Wheesley" Turbofan Engine (haven't unlocked better engines yet) I get close to 500m/s cruising speed at 11500m altitude with a quick-and-easy assembled plane (nothing optimized, it just flies good enough for me).

[AHHans]

55 minutes ago, XLjedi said:

What have you been seeing for max sustained cruising speeds on your turbo-fan designs?

Which turbofan engines are you talking about?

In a light plane with the panther afterburning turbofan I can supercruise (> mach one in dry mode) and easily manage more than mach 2.5 in wet mode.

[XLjedi]

Yeah, I quoted the wrong name.  The new robotics parts... it's the "ducted fan" not the "turbo fan".

So disregard the two turbofan responses above (my fault), and I will restate the question with the correct name of the robotic fan part.

[AHHans]

19 minutes ago, XLjedi said:

The new robotics parts... it's the "ducted fan" not the "turbo fan".

Kind of what I thought, but I couldn't resist a snarky comment.

I haven't used the ducted fans myself (yet?), but 250 m/s is more than my propeller planes manage. I haven't built a speed-optimized craft, but I wouldn't be too surprised if 270 m/s or so is a hard upper limit.

[XLjedi]

36 minutes ago, AHHans said:

Kind of what I thought, but I couldn't resist a snarky comment.

I haven't used the ducted fans myself (yet?), but 250 m/s is more than my propeller planes manage. I haven't built a speed-optimized craft, but I wouldn't be too surprised if 270 m/s or so is a hard upper limit.

I circumnavigated the globe (Kerbin) this weekend with an average sustained speed of 275 m/s and I was pretty happy with that.  It was almost exactly a 4 hour trip (4hrs and 5 mins, but I made a brief full-stop at Dessert Base, so a bit inside of 4hrs is probably what I would assume for a non-stop effort)  Average altitude was about 1500m and on a few occasions when I had climbed up to about 2500m and was coming back down to 1000m I managed to peak out above 290 m/s with a few reasonably long runs in the 280 m/s range.  ...but I 275 m/s (Mach 0.8) is kinda my expected benchmark now.

I know the same craft with a dual Juno jet setup topped out at 305m/s at an altitude of about 5000m... but the Junos have a hard time getting anywhere near 270 m/s in the 500-1500m low altitude range. 

The fuel economy of the ducted-fan was the remarkable thing.  I made the trip on a 270° heading (which forced a much longer night sequence) so I would say at least 75% of the flight was in complete darkness and I still had like 82% of my fuel reserves remaining when I touched down at the KSP.

I was going to do an "Electric-Jet" video on the setup but wanted to see what others may have seen in terms of their own ducted-fan design performance.  In a sprint, dual ducted-fans can beat dual junos to the island runway every single time.  They accelerate faster and hit a top speed on the island run inside of 3 minutes that the Junos can't match.

With dual Junos, I can make the trip to the Dessert Facility on maybe a bit under 50% of fuel...  So I think a round-trip is do-able with those engines provided I'm maxing out efficiency at about 5000-6000m altitude range and cruising speed in the 305 m/s range.  The ducted-fan makes the trip at an average speed of about 275 m/s and used less than 3% of available fuel reserves, with the ability to use zero fuel if the sun was shining the whole time. 

Both planes are using the same airframe shown here:

Spoiler

https://kerbalx.com/XLjedi/HU-26-Guardian

 

Edited December 16, 2019 by XLjedi

[VoidSquid]

1 hour ago, XLjedi said:

So disregard the two turbofan responses above

<kidding>
Disregarding my answer, eh? And why did I read your question in the first place? Processed it? Tried to come up with an informative and helpful answer? Hmm? All for nothing? That's very, very naughty of you!  
</kidding>

All good, no worries, see you in space  

[Lt_Duckweed]

Max I've been able to get on kerbin is 376 m/s with an RTG powered plane.

Max overall was on Jool (higher speed of sound thanks to the hydrogen atmosphere) where I got a bit over 800m/s with the exact same plane.

[Fierce Wolf]

Ever tried time warp with fan blades? Funny business (not really, the ship will crash hard)