makes no sense. Instead of carrying extra gas, just increase the propellants going into the engine
Quote from: Jim on 03/02/2023 12:01 ammakes no sense. Instead of carrying extra gas, just increase the propellants going into the engineThis was a real observed effect that gained thrust per amount of air involved. Net Isp at sea level would improve. Increasing propellants requires increasing pressure and pump size. This is about getting more performance out of a given engine.
I was using threads in the nozzle in the same manner as yarn tufts on aero surfaces to watch flow patterns. Never Hearn of yarn tufts giving a false reading.
Jim,It only takes one person duplicating my results to refute your objections.
Not at all. The result is that the secondary jet kicks the flow off of one wall and lets the atmosphere interact with the follow in the same manner as an aerospike. Or if you prefer, it shortens the effective nozzle length at lower altitudes.
Actually I do know that.
It’s clear to one knowledgeable in the field.
Quote from: sevenperforce on 03/03/2023 02:13 pmWhat is your argument here, exactly? That adding pressure to one side of the nozzle can prevent flow detachment at the other side of the nozzle?Not at all. The result is that the secondary jet kicks the flow off of one wall and lets the atmosphere interact with the follow in the same manner as an aerospike.
What is your argument here, exactly? That adding pressure to one side of the nozzle can prevent flow detachment at the other side of the nozzle?
That is the key question on any different system added to a standard engine. New systems must necessarily be guilty until proven innocent.
I stumbled across this while working on something else right about the time the recession decided I didn't need to have extracurricular activities. Going from the aerospike side, I never looked at LITVC closely. Also, when I ran some numbers, thrust augmentation seemed to gain more from reducing losses than actual thrust.
It doesn’t add thrust. It decreases the losses from pressure at exit being lower that the atmospheric pressures at low altitudes.
I never really understood why NASA didn't pursue it. Their massive phobia about averting risk? Lack of a current mega-project to use it on? Who knows.
**Should work technically is totally different than guaranteed to work in hardware. And even further from being a good idea from the business side.
This concept appears at least in principle to be related to the technique of Liquid Injection Thrust Vector Control. A liquid is injected into the exhaust stream partway down the nozzle. It vaporizes, creating a stream of gas which pushes the main exhaust stream to one side. For economy, the liquid can be an oxidizer, which reacts with the fuel-rich exhaust gases to generate hot gas. A ring of injectors can be used to vector the exhaust of what is typically a solid rocket. The Titan launcher solid rocket boosters used injection of N2O4 to vector thrust from a fixed nozzle.When thrust is vectored, there is a small additional increment in thrust related to the additional mass flow, and potentially due to changes in the expansion of the main rocket exhaust which is "squeezed" into a smaller area (similar to the proposal being discussed here). Potentially, a ring of liquid injection ports all working at the same time would symmetrically create extra gas which would squeeze the main exhaust away from the nozzle walls and increase its exit pressure, reducing the overexpansion losses at sea level. As the rocket rises, the flow of liquid injection would be tapered off to match the reduction in atmospheric pressure. Whether it is worth the trouble (extra mass, extra equipment) is not clear without detailed calculations.
Flow in a nozzle is supersonic; nothing you do downstream can impact anything upstream. And thus the expanding exhaust cannot provide thrust to the nozzle unless it is actually in contact with the nozzle.
Quote from: sevenperforce on 03/06/2023 03:40 pmFlow in a nozzle is supersonic; nothing you do downstream can impact anything upstream. And thus the expanding exhaust cannot provide thrust to the nozzle unless it is actually in contact with the nozzle.Those are convenient simplifications, not truisms. Otherwise, gas generator exhaust injection into the nozzle bell would cause a drop in both thrust and propulsive efficiency (instead it increases both), and exhaust gas recirculation around a vehicle's aft section would be impossible (when in fact it is both possible, observable on images and video of vehicles in flight above the atmosphere, and a factor that needs to be taken into account for thermal modelling).
Not fluid injection in what I started with. An energetic counter flow to detach the flow off of one side such that the atmosphere can fill the void.
Quote from: redneck on 03/07/2023 10:36 pmNot fluid injection in what I started with. An energetic counter flow to detach the flow off of one side such that the atmosphere can fill the void.So, precisely what I showed in the image, but with gas being blown up from the nozzle lip on one side rather than fluid being injected down?