Boeing-Sikorsky SB>1 Defiant (Model S-100)

H_K said:
yasotay said:
"Twice as far, twice as fast" requires twice the horsepower
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Actually since the UH-60’s engines are ~2,000shp it’s more like 3.5x the horsepower… hopefully the tactical advantages are worth it.
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Yeah, velocity is squared so essentially you have to have 4x the power to go twice as fast, assuming everything else being equal. And considering Defiant is a goddamn whale...
 
It's a banal error. I have explained that already so, sorry if it sounds a bit pedantic.

We assume generally in that kind of problem that engine power here compensate only for the drag. We also assume that drag is the dynamic drag, 0.5*rho*V^2*S (S being the surface of reference).

So in effect, it's correct to assume that when the speed is doubled, the dynamic drag is quadrupled (2V)^2=4V^2.

However, the power is the product of the Effort (here the drag) time the speed.
Hence 0.5*rho*4V^2*S*2*V=0.5*rho*8*S*V^3
Which is 8 time more than before!

That's a bit different ;)
 
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flanker said:
H_K said:
yasotay said:
"Twice as far, twice as fast" requires twice the horsepower
Click to expand...
Actually since the UH-60’s engines are ~2,000shp it’s more like 3.5x the horsepower… hopefully the tactical advantages are worth it.
Click to expand...
Yeah, velocity is squared so essentially you have to have 4x the power to go twice as fast, assuming everything else being equal. And considering Defiant is a goddamn whale...
Click to expand...
Kinda goes with being a cargo helicopter. ;) (And lets' not forget all that extra HP translates into lots more fuel required.)
 
TomcatViP said:
A turboshaft in the 7000shp class! And defiant has 2 of them...
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Indeed lots of excess power that can be converted into lift and/or thrust as required. Btw, the turboshaft engines of the C-130 have a power output of ~4500 shp each.
 
VTOLicious said:
TomcatViP said:
A turboshaft in the 7000shp class! And defiant has 2 of them...
Click to expand...
Indeed lots of excess power that can be converted into lift and/or thrust as required. Btw, the turboshaft engines of the C-130 have a power output of ~4500 shp each.
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A CH-53K has more HP than a C-130 and the same as the Mi-26 (22,500hp). (Though the Mi-28M bumped that up to a total of 27,600hp.)
 
I was referring to the C-130 because of its turboprops. I would assume Defiant's prop consumes a similar amount of power in cruise flight above 200 kts.
 
@Cordy : It's not the final engine! But we can see how the SB-1 config has a range much more related to its engine than Valor. Valor uses a winged configuration with all the inherent benefits on the cruise portion.

The US Army has certainly long realized that Defiant will never meet Valor on that segment of the mission. Hence, I don't think that, at this stage, where there is only two competitors left, this will bear any consequences. FATE or not fate.
 
With the down select looming this summer (if not delayed), a demonstration of long range flight is likely one of the last test cards. With the Army Aviation meeting at an appropriate distance, you can get the test done, and show off the product to the customer.
 
A 30 year old AW101 could have flown that mission faster, farther, with 2.5x the payload, and without stopping. Same size class.

… just to put the performance in context.

(I know, I know... Defiant may still have room to improve. Though honestly I'm perplexed why they only cruised at 175kts).
 
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VTOLicious said:
TomcatViP said:
A turboshaft in the 7000shp class! And defiant has 2 of them...
Click to expand...
Indeed lots of excess power that can be converted into lift and/or thrust as required. Btw, the turboshaft engines of the C-130 have a power output of ~4500 shp each.
Click to expand...

One has to wonder if, at some point, that excess power would be better spent on a DEW rather than on speed? I wonder what the threshold is?
 
H_K said:
A 30 year old AW101 could have flown that mission faster, farther, with 2.5x the payload, and without stopping. Same size class.

… just to put the performance in context.

(I know, I know... Defiant may still have room to improve. Though honestly I'm perplexed why they only cruised at 175kts).
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I must admit I am a bit perplexed myself at the rather mundane performance for this particular effort. It may be that there are insurances or FAA limitations that apply to an experimental aircraft of its size.
That is a wild guess on my part.
 
We'll see how that turns out. It's up to the customer... However, both teams have delivered impressive technology demonstrators so far. I would love to see a picture of them next to each other ;)
 
yasotay said:
That is likely a picture that Sikorsky would rather not see on the internet. I believe it is significantly larger than a CH-47 main module.
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It is freaking massive, even in comparison. But then, the space and weight of the Chinook combining transmission doesn't include the two other boxes fore and aft, or the the six shafts running from the pods to the combining box, down the length of the fuselage fore and aft, and up to the rotors in the Chinook.

What is pictured at the link seems to include the entire mast and the shafts to the engines (to cameras left), and then missing one longer, but lighter shaft to the prop.
 
VTOLicious said:
yasotay said:
That is likely a picture that Sikorsky would rather not see on the internet. I believe it is significantly larger than a CH-47 main module.
Click to expand...

But one shouldn't forget that the Chinook actually has 3 gearboxes.
View attachment 688061
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Yes, to the rotors, and if you notice, two more small transmissions directly shafted between the combining box and engines.
Defiant will have those, too, and in the photo, one of them is visible. The package is facing the wrong way to see, but the Defiant setup likely includes the box to the prop shaft as well as the other engine transmission.
 
VTOLicious said:
The CH-53's main gear box appears to be of a similar size...
View attachment 688066
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Ch-53K has a gearbox that is predictably even larger.

5c59c607936c0e68e83fae4a

US Marines load the main gear box of the CH-53K King Stallion at Marine Corps Air Station New River, North Carolina, October 3, 2018
Photo credit: US Marine Corps/Cpl. Ethan Pumphret
 
Defiant- Blackhawk pic set...
 

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https://www.thedrive.com/the-war-zone/sikorskys-protest-of-bells-v-280-win-over-its-sb1-shot-down

"In denying the protest, GAO concluded that the Army reasonably evaluated Sikorsky’s proposal as technically unacceptable because Sikorsky failed to provide the level of architectural detail required by the RFP.

GAO also denied Sikorsky’s various allegations about the acceptability of Bell’s proposal, including the assertion that the agency’s evaluation violated the terms of the solicitation or applicable procurement law or regulation.

Finally, GAO dismissed Sikorsky’s additional arguments on the basis that Sikorsky was no longer an interested party to further challenge the procurement."
 

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