Fenris rather than Sabre

[theJesuit]

So I read this this morning:

https://arstechnica.com/science/2020/06/the-rocket-motor-of-the-future-breathes-air-like-a-jet-engine/

And wondered how the idea could be applied to KSP... as an alternate to the Rapier.

So I was thinking that you have an air intake that doubles as a convert a tron.  You then have IntakeAir converted to Oxidizer 'on the fly' as it were.  The intakes that are supposed to be supersonic intakes do this faster as they are collecting more air anyway.  But you'd only have the supersonic's do this.

Then use regular rocket engines as per normal. You just don't have to carry as much oxidizer.

Now I totally agree that with as the weight of Oxidizer is so similar to LiquidFuel in the stock game that this might not be practical.  It would be better if the rocket burn ratios in stock were different as they are in some mods which changes the .9/1.1 ratio to 1/3. So this would be with mods in mind obviously.

There might also be a caveat... that their is a requirement for high EC to do the conversions. And also extra mass. That could offset with engines that are also alternators. 

Happy to hear what people think.

[Weimaraner]

A nice idea, OPT has scramjets, but they work in the same way as the rapier. I would like to see this too.

[Clamp-o-Tron]

Although it sounds awesome for KSP, IRL it seems sketchy. 600+ isp for any chemical engine is a massive technological feat, but for (implied, correct me if I'm wrong) kerosene? I doubt it, not to mention its physically impossible. It sounds valid, but probably not from a company making this kind of claims.

[theJesuit]

9 hours ago, Clamp-o-Tron said:

Although it sounds awesome for KSP, IRL it seems sketchy. 600+ isp for any chemical engine is a massive technological feat, but for (implied, correct me if I'm wrong) kerosene? I doubt it, not to mention its physically impossible. It sounds valid, but probably not from a company making this kind of claims.

Oh I totally agree.  I'm thinking that if I mod this in myself, it will be a very late game thing - sitting alongside Aluminium + Oxidizer rockets in terms of 'is this ever going to happen'?'

 So another wee thing to add to Simplex Propulsion if that ever gets an update pass .

Peace.

[DStaal]

14 hours ago, Clamp-o-Tron said:

Although it sounds awesome for KSP, IRL it seems sketchy. 600+ isp for any chemical engine is a massive technological feat, but for (implied, correct me if I'm wrong) kerosene? I doubt it, not to mention its physically impossible. It sounds valid, but probably not from a company making this kind of claims.

There's actually a good discussion thread on the article linked above.  General consensus in the thread is that the tech will probably eventually work just fine on the test stand, at sea level, at Mach 0.0.  However that's not even half the problem solved - getting it to work at hypersonic speeds and upper atmosphere will be it's own massive issue - and probably negate any mass gains from the fuel you don't have to carry.  (Not to mention you may have to stay *in* the atmosphere longer, increasing drag...)

Fully agree it would be interesting to have in KSP however.

[JadeOfMaar]

On 6/27/2020 at 6:40 PM, theJesuit said:

So I read this this morning:

https://arstechnica.com/science/2020/06/the-rocket-motor-of-the-future-breathes-air-like-a-jet-engine/

And wondered how the idea could be applied to KSP... as an alternate to the Rapier.

1. So I was thinking that you have an air intake that doubles as a convert a tron.  You then have IntakeAir converted to Oxidizer 'on the fly' as it were.  The intakes that are supposed to be supersonic intakes do this faster as they are collecting more air anyway.  But you'd only have the supersonic's do this.
2. Then use regular rocket engines as per normal. You just don't have to carry as much oxidizer.
3. Now I totally agree that with as the weight of Oxidizer is so similar to LiquidFuel in the stock game that this might not be practical.  It would be better if the rocket burn ratios in stock were different as they are in some mods which changes the .9/1.1 ratio to 1/3. So this would be with mods in mind obviously.
4. There might also be a caveat... that their is a requirement for high EC to do the conversions. And also extra mass. That could offset with engines that are also alternators. 

Happy to hear what people think.

* Items given numbered bullets for sorting as I approach them.

1. IntakeAir being processed into Oxidizer on the fly is effectively half of a Liquid Air Cycle Engine. Some mods may already offer this. One of mine (Kipard Skylon) has this as an optional upgrade. I created it as I thought it was part of how SABRE works but I got pointed out by someone sometime afterward that LACE is very much not part of SABRE. LACE (afaik) also requires sacrificing LH2 fuel to provide enough coolant power to flash hypersonic IntakeAir into cryo liquid form.
2. As consequence of this, I made it so that Skylon's tanks could hold LF or LH2 alone (B9's fuel switch) so if ever a player needed much more fuel volume or (through plenty testing) much less Oxidizer volume, they could achieve it without clipping Mk1 LF tanks.
3. See point #2. Part of why I created Rational Resources is so I can answer this fuel ratio problem with fuel switch (as an extras config) so I'll never have to think about changing the fuel ratio in engines. There will always be someone who will want to use your specific engine in a way it's not meant to, or anywhere outside of the edge case you made it for. And you'll get complaints about that. I know this from my WIP mod SABR3 Sterling. Some players gravitated to the  discreet rocket nozzle part because it offered higher Isp than the RAPIER's closed cycle. I immediately foresaw this problem and I was glad I never let loose any custom fuel ratio configs.
4. High EC demand to buff the Helium coolant loop's ability, or having the precooler (in-game) use a non-transferrable catalyst that gradually degenerates (instilling a half-life mechanic) due to the hypersonic plasma entering the intake are both good options to consider. Related, my SABR3 intakes use a novel method of producing a metaphorical catalyst resource (named MillPower in my case, representing a converter's capacity to do the job at a given velocity) through its own intake module only when a certain minimum speed is met (see machCurve{} inside ModuleResourceIntake{}) and having an always-on converter consume this catalyst and IntakeAir to produce Oxidizer.
   
   On half-life: The SABRE heat exchanger spiral contains countless fine filament like structures or holes that physically stop and flash cool air at the particle level, so surely, the sheer heat will corrode this in due time IRL.

On 6/27/2020 at 7:34 PM, Weimaraner said:

A nice idea, OPT has scramjets, but they work in the same way as the rapier. I would like to see this too.

Where OPT is concerned, you want to look at the circular ARI-series engines. These can correlate (to whatever degree) with the Fenris. My impression of Fenris is that it is an air-augmented engine which uses ram air effect to complement its rocket engine nature, though, unlike Fenris, the OPT ARI don't use LACE, and no OPT intake or converter offers the LACE effect. In KSP this typically means an increase of Isp, and by extenision, thrust.

Note: The OPT ARI engines are specially tuned to not produce insane thrust when in atmosphere (where their Isp is much higher) vs thrust in vacuum.

 

16 hours ago, Clamp-o-Tron said:

Although it sounds awesome for KSP, IRL it seems sketchy. 600+ isp for any chemical engine is a massive technological feat, but for (implied, correct me if I'm wrong) kerosene? I doubt it, not to mention its physically impossible. It sounds valid, but probably not from a company making this kind of claims.

My point #4 above introduces the use of machCurve{} inside of ModuleResourceIntake{} to force a speed requirement on one of the inputs for a converter. You can approach gameplay balance from an existing opposite angle. Assuming Fenris is an air-augmented rocket, you can use velCurveIsp{} and useVelCurveIsp = True inside ModuleEnginesFX{} to have the engine's Isp change with velocity in atmosphere. Players will then be forced to use the engine at length in atmosphere to access the Isp buff. The OPT Mk2 scramjets use velCurveIsp for their Isp falloff at hypersonic speeds, escaping the need for a separate engine module for operation there.

Without forcing a dependency on CryoEngines I'd appropriately nerf the max Isp on the engine. 360 ~ 400 is a good upper limit range on any Kerosene engine.

Edited June 29, 2020 by JadeOfMaar