[AR] Re: Closing the loop on rocket engines

  • From: Anthony Cesaroni <acesaroni@xxxxxxxxxxx>
  • To: arocket@xxxxxxxxxxxxx
  • Date: Thu, 10 Dec 2015 20:28:38 -0500

No one has ever tested and verified that those engines produce that much power.
It's a hyped estimate based on flawed assumptions.
Anthony.

Sent from my iPhone

On Dec 10, 2015, at 7:59 PM, Monroe L. King Jr. <monroe@xxxxxxxxxxxxxxxxxx>
wrote:

Try out some 10,000hp action https://www.youtube.com/watch?v=CN4uAQzI1rs

Rocket guy's are cool don't get me wrong. But this is where I'm coming
from.

-------- Original Message --------
Subject: [AR] Re: Closing the loop on rocket engines
From: "Troy Prideaux" <GEORDI@xxxxxxxxxxxxxxxx>
Date: Thu, December 10, 2015 5:08 pm
To: <arocket@xxxxxxxxxxxxx>


To illustrate that last point with a comparison: let’s take the Merlin 1C or
1D combustion chamber only.



It’s small enough to fit under the bonnet of just about any car on the road
and probably light enough to be carried by a single man.

Propellants LOX:PR1 at ~2.36 O:F ratio

Feed rate: 140Kg/s (for the 1C say)

Now for that propellant combination I calculate a c* of ~1690 m/s at optimal
mixing

So, specific E Joules/Kg = (1690^2)/2 = 1430823

So incorporating flowrate 1430823 * 140 = 20,031,521 J/Kg

Converting to Power = ~20 MW



Note: that’s just the chamber only.



Now compare to a super-duper $mega sports car:

What, they max out at about 1000HP? Which is ~0.75MW?

That’s with an engine that’s substantially larger and much much heavier.



Feel free to correct any of my BOE calcs..



Troy







From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On
Behalf Of Andrew Burns
Sent: Friday, 11 December 2015 5:17 AM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Closing the loop on rocket engines



There are several differences between rocket engines and car engines that
are key to this discussion:

- Rocket engines need only work for a few minutes at a time before being
thrown away (generally)

- Rocket engines operate with very tightly defined propellants at controlled
temperatures and pressures and within a very narrow operating window

- Rocket engines are normally essentially binary, on or off, they're not
normally dynamically throttled

- Rocket engines have an absolutely immense thrust/power to weight ratio
compared to car engines and are accordingly so much more highly stressed



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