[WIP][Part/Plugin] The RAT Pack - Ram Air Turbines, Terrain Warning, Thrust Reversers

[satnet]

After noticing a sharp rise in crashes Gene Kerman commissioned a study on why rockets and planes crash. The resulting 3,151 page report was turned over to SatNet Aerospace to research and develop parts that could reduce crashes or make them more survivable. The first parts to come out of the project were Ram Air Turbines and the group was quickly dubbed “The RAT Pack". Even as they expanded into more flight safety parts the name stuck.

 

The RAT Pack:

Ram Air Turbines

The RAT Pack provides Ram Air Turbines that generate power from flowing air. I was partly inspired by a documentary on the "Gimli Glider", a 767 that had to glide to a landing with nothing but batteries and a RAT to power critical systems. A couple of spaceplane landings where I had to constantly manage electric charge to maintain control and keep enough for the landing gave me some incentive to actually build it. The RATs are designed to provide emergency power and have peak power at or slightly above that of an RTG. Electric charge output is a function of both airspeed and atmospheric density.

 

• RAT-1 "Pinwheel" Ram Air Turbine - As basic as they come, it provides little power and must be activated manually.
• RAT-360 "Cage Master" Ram Air Turbine - Generates more power and will automatically start up when electric charge is depleted.
• RAT-720 "Topper" Ram Air Turbine - A RAT built into a nosecone. It has a higher peak power than the RAT-360, but has a performance curve similar to the RAT-1.
• RAT-6000 "Pack Master" Ram Air Turbine - The most powerful RAT. This one has the ability to control electric charge flowing from its internal battery and turns it on only when it is activating. It is able to generate peak power over a broader range.
• EPM-MK3 "Emu" Emergency Power Unit - A complete emergency power solution with a RAT, Fuel Cell, and APU.

 

Thrust Reversers

Thrust Reversers redirect the engine thrust. They are used to reduce stopping distance once landed. I developed it primarily for Duna spaceplanes where a short stopping distance is a huge asset. They will redirect the thrust of the engine attached to them. Attaching multiple engines will not give you the desired behavior as only one engine will be reversed.

• TR-1 “Backup" Thrust Reverser - Designed to fit a Turbojet or RAPIER engine.
• TR-L “Way Back" Thrust Reverser - Designed to fit longer 1.5 m engines, particularly the LV-N.

 

Terrain Awareness and Warning Systems

A Terrain Awareness and Warning Systems (TAWS) gives you a chance to avoid a crash by warning you while you still have some time to react. It uses the radar altimeter and some calculations to figure out what the terrain looks like. It also has an obstacle detecting radar (FLT Radar), however it only activates below a certain altitude and uses a fair amount of power when in use.

• TAWS-1 "Lookout" Warning System - Equipped with Ground Proximity Warning System (GPWS) and Forward Looking Terrain (FLT) Radar.

• TRS-1 "Lookdown" Terrain Radar - Terrain scanning to improve landings.

Launch Escape System Trigger

I came across this post Launch Escape System Rocket Stack Failure Detection and thought it was in line with this mod and a great idea.

• LEST-1 "Oops" LES Trigger - Detects a unplanned dis-assembly and hits the abort button for you.

 

Download:

https://github.com/KSatNet/RATPack/releases/download/v0.21/RATPack.zip

Source:

https://github.com/KSatNet/RATPack/tree/master/RATPack

License:

https://github.com/KSatNet/RATPack/blob/master/RATPack/LICENSE.md

Questions and Answers:

Spoiler

 

Q: Are these RATs realistic?

A:Somewhat. The power curves where inspired by real RATs, but have been heavily Kerbalized.

Q: Why doesn't my speed on the power curve match my vessel speed?

A: The RAT uses an effective speed calculation that takes into account orientation, parts blocking airflow, and pressure. It will only match up with vessel speed at sea level, going straight, and without anything in front of the part.

Q: Where can I use RATs?

A: Anywhere with an atmosphere. Kerbin, Duna, Eve, Laythe are all good places to use them. Jool and Kerbol might work, but you'll probably be crushed or melted before you get any power.

Q: What happens if I run out of power landing on the Mun with a RAT?

A: You will probably hit the Mun and the RAT will be destroyed.

Q: What happens if I run out of power landing at the KSC with a RAT?

A: If you have an auto-activating RAT it will deploy and start generating power. If it is a manual RAT, you can't activate it after losing power, so prepare for high speed lithobraking.

Q: Do RATs work inside fairings or cargo bays?

A: No, they need to be in the air-stream.

Q: How does orientation affect RATs?

A: Yes, they produce the most power when pointed in the prograde direction.

Q: Can I fly backwards using a thrust reverser?

A: Yes, though it is not recommended. Most planes and rockets are not aerodynamically stable in both directions.

Q: How much thrust will a thrust reverser reverse?

A: Short answer – you lose a lot of thrust, but it should be enough to stop quickly. Long Answer – Each TR has a thrust modifier which defaults to 50% intended to account for thrust lost to exhaust escaping to the sides. Additionally the thrust direction is not directed in reverse, but in a 45 degree angle above and below the engine. The net thrust is in reverse, but there are significant losses from the thrust directed up and down that cancels out.

Q: Will a thrust reverser work in space?

A: It will, though you are effectively reducing your engine efficiency, so you are better off re-orienting.

Q: Why doesn't my descent rate match my vertical speed?

A: They are similar but different values. Descent rate is probably better described as ground closure rate. It is how quickly you are approaching the ground. Vertical speed is how quickly you are changing altitude relative to a common reference radius (i.e. sea-level). If you are on level terrain they will be the same. If however the ground is rising relative to sea-level you will have a higher ground closure rate than vertical speed which is a really important distinction when deciding whether you will hit the ground at some point in the near future.

Q: Will I always have time to pull up when TAWS issues a warning?

A: Not necessarily. The current values are very... "Kerbal", they give you a chance at survival, but no guarantees. If you aren't trying to hit terrain it is usually enough warning to avoid the occasional near miss, but if you deliberately try to test the limits you will hit the ground at least some of the time. You can set your own values, but I found anything that would ensure survival was too conservative for the way I fly in game.

 

 

 

 

 

NOTE: I'm referencing the stock textures. If you modify or remove textures from the stock parts these parts will fall back to the solid black placeholder texture.

Edited December 1, 2015 by satnet

[MaverickSawyer]

Very clever! I like the idea.

[satnet]

Second beta release is up. I've decided to expand the scope to Flight Safety tech in general rather than RATs specifically. It was just too limiting, though I did keep "The RAT Pack" name with a little back story so it still made sense. The first part in this new line is a thrust reverser that works with whatever engine you attach to it.

Edited October 20, 2015 by satnet

[Svm420]

Wow great work very unique!

[Reiver]

Oh, this is neat. Now I can stop slapping batteries onto my spaceplanes just so they've got enough charge for glider landings.

The RAT systems do sound a little like they are very much a 'each one is better than the last' progression - is this the case, or are there pros/cons beyond simple cost?

[TrainEngie]

Attachable thrust-reversing modules? OMG!

[satnet]

The RAT systems do sound a little like they are very much a 'each one is better than the last' progression - is this the case, or are there pros/cons beyond simple cost?

Right now each is better than the last (except cost, weight, and size). Once you have later ones unlocked there isn't much reason to go back. I plan to have a nosecone and MK3 sized version at some point for a little more variety, but this set seemed like a good start.

[Reiver]

Hm. I can certainly see a method for diversifying them, if you wish:

• The RAT-1 is very similar to modern aircraft emergency power supplies. It'd be neat if it was drag-free folded down, if draggy when active. It'd produce power even at relatively low speeds, but have limits on higher ones - perhaps overheating and/or speed limits like solar panels and parachutes when open, so you'd not want to use it during re-entry or RAPIER-powered ascents.
  
• The RAT-360 solves the speed problem, but is heavier, and prefers speed entirely; it doesn't do well at low speeds. Use it to recharge on your way down (Or maintain power on that RAPIER plane), but be cautious of trying to use it for emergency power in landings!
  
• Then your RAT-6000 is the current does-everything (Fast, slow, speedproof, and power management to boot) but is expensive and heavy enough that you actually care. Great for big craft and serious auxiliary power, but not so much a backup option...
  

I note in passing that yes, these are pretty similar to what you already do - it's just giving each one an explicit purpose whilst still drifting towards later models being 'better' as the tech improves. But at least then you've still got a perfectly legit use for the RAT-1, even if it's simply as a very lightweight emergency power for your landings that you never plan on needing... but might regret if you don't. It's the Kerbal way, of course.

A nosecone one would be pretty neat. You mean a .6m cone, right? I have glorious visions of sticking it on the top of the OCTO cores of my aerobraking probes

Edited October 20, 2015 by Reiver

[satnet]

Reiver - Thanks for the suggestions. I'm planning a re-balance before I release and I'll incorporate some of your ideas. Yes, a .6m nosecone is what I have in mind, but I'm not sure when I'll get to it.

[Reiver]

Awesome

A small note on the utility of the suggested RAT-360: You can use it to maintain power on aero-braking probes when their solar panels had to be folded away. It's worth noting that this is also when a vehicles power drain can be highest (Because it'll frequently be aggressively using reaction wheels to try and control itself), so this could provide a great offset to needing spare batteries.

I was trying to design a jool-diving probe just yesterday and realised how incredibly handy a lightweight high-speed optimised RAT would be... so now I'm even more impatient for this mod than ever.

[satnet]

First release candidate is up.

Major Additions:

TAWS-1 A terrain warning system.

RAT-720 A RAT built into a nosecone.

Major Changes:

Rebalanced everything. Most of the RATs produce more power. RAT-360 is now the most consistent. RAT-6000 produces a lot of power, but is much heavier. RAT-720 produces more charge than RAT-360, but the performance curve is the same as the RAT-1. Thrust reversers produce more thrust (still a fraction of forward thrust).

[Reiver]

Awesome.

What do the performance curves look like for these?

[satnet]

Everything is in indicated airspeed which is actually a function of both speed and pressure (lower pressure means lower indicated airspeed).

RAT-1 Peaks at around 100 m/s and drops off quickly.

RAT-360 Peaks at 50 m/s, stays near 100% up to mach 1, and drops off slowly.

RAT-720 Same as RAT-1, but much more power than RAT-1/RAT-360.

RAT-6000 Peaks at 50 m/s stays near 100% up to 250 m/s, and drops of more quickly than RAT-360. More power generation than any of the others.

RAT-1 Cheap, light, disposable.

RAT-360 is the best option if you want consistent power.

RAT-720 has the nosecone form factor and produces a lot of power.

RAT-6000 produces a lot of power and is fairly consistent.

Here is a graph.

[Reiver]

That really does make the RAT-360 look like the Best Solution. Not sure how I feel about that. I'll have to fool around with them in play and see.

If the RAT-1 and RAT-720 had proportionately better performance than the 360 at lower speeds, the drop-off would mean everything has a point... in the right circumstances.

[satnet]

What about this as an alternative?

[Reiver]

Promising. How much would RAT-1 cost & weigh compared to RAT-360 with that setup? I'd also be inclined to give the pair of them an 'optimum range' like the RAT-6000, even if it's just 100-300m/s or so, so that deliberately trying to use it to charge your craft is more convinient.

The RAT-6000 could actually do with having a flatter taper-off in this scenario; it's meant to be the heavy-duty, does-it-all after all

(Just to check - that chart isn't suggesting that the RAT-720 produces 1e/s whilst stationary, is it?)

[satnet]

RAT-360 would weigh/cost about double RAT-1. RAT-720 is about 2.5 times cost/weight (and gets about 2.5 times the charge).

No, none of them would produce anything totally stationary. It just looks that way because of the scale. They do rise pretty quickly, but at low speeds or high altitudes they still produce minimal charge.

Another refinement of the curve:

[satnet]

Second release candidate is up. The only change was a rebalance of the RATs. Primarily the performance curves were changed, though I did notice that the RAT-720 cost less than the equivalent nosecone, so it now costs more.

The performance curves ended up basically like my last post. I did change them a little after trying them out in game, but the basic idea remains intact.

[Reiver]

I have a slightly different suggestion, based on the fact that this is what a power curve often looks like:

Note the inability to do much at all, then rapidly climbing to peak power, and then dropping off once the safeties kick in and prevent it producing power at all. (The gradual drop-off from peak power is as the turbines have to start worrying about not spinning so fast; there's too much of a good thing when it comes to wind speed!)

I've thrown together a (really) rough 'kerbalised' version below. I removed the power drop-off; you could put it in again if you like, but I figure flattening out the top of the curve so you have an 'optimal range' of several hundred meters per second would make it easier; having an 'optimum speed' that's pretty much right before power output starts plummeting while you decelerate could certainly add realism and a little bit of challenge if you'd rather it that way, though!

A couple other notes: None of them would produce power before 30-50m/s; while a little unrealistic I'd be concerned about people building 'perpetual rovers' with electric wheels otherwise; they don't seem to respect drag effects and fun RAMs are far more power-efficient than 'real' RAMs, sooo...

Note how you want a RAT-1 or RAT-720 for regular landing and versatile lower-speed power, but the RAT-360 can even power deorbiting manoeuvres at the cost of subsonic utility; while less specialised the RAT-6000 will pretty much 'do it all' unless you're specifically interested in one extreme over the other. (Given that in this model the RAT-1 and RAT-720 have much more restrictive power curves, you could probably get away with their having better power:weight/power:cost outputs; possible a titch more power for the RAT-1 and the RAT-720 being good value, or the like. I leave that sort of thing up to you.

If you could rig their power to be dependent on airflow direction like intakes, that'd be even more fantastic, but I've no idea of how viable that is.

Actually, even as I write this post I kind of regret not putting the gradual power-drop after the optimal peak, more closely fitting the top shape; trying to juggle an unfueled return vehicle to stick in the 'sweet spot' to keep power flowing into the batteries could add one more delicious headache to landings! Still, hopefully this gives a useful guideline? If not I could try something a little more detailed and less rushed; I've an early start tomorrow.

EDIT: An 'advanced' version:

This one leaves the RAT-360 as unique; presumably it's some sort of feathered turbine configuration or the like, but either way it doesn't hit the safety brakes like the other ones, and the RAT-6000 took notes.

And now, really bed. I'll clean this post up tomorrow.

Edited November 5, 2015 by Reiver

[satnet]

Wow, thanks for putting that together. Unfortunately, I went ahead and released the first version. I was concerned about releasing right after 1.0.5 came out and figured right before was better. I'm planning another release after 1.0.5 comes out with Mk3 parts to go with the improved Mk3 parts in the release. I'll incorporate these curves in that release (expect a mention in the changelog/post 'Updated power curves by Reiver').

It would be possible to make them dependent on airflow direction. A rework of the power calculation is probably in order for 0.20 which would be a good time to incorporate that behavior. I'll definitely have a cutoff. I hadn't thought about the perpetual rover problem, but you're right.

[Reiver]

Yeah, in the ideal world you'd have those curves decay neatly to zero, but with the current motor/physics model, that can have unintended side-effects, so we'll have to make do with hard cutoffs.

Speaking of, there's a typo in that chart - the RAT-1 should be climbing to 0.8, 1.0, 0.8 again. The intent was the 'build up' and 'drop down' were to the same values; while kerbalised it helps people plan a little easier - a rapid climb, an even more rapid descent (for the two 'low speed' generators, anyway), and a more gradual hump in the middle, biased towards the lower speed. Because that's (very) approximately what those curves look like.

Edited November 9, 2015 by Reiver

[satnet]

Uploaded version 0.11.

- Updated power curves by Reiver

- Mk3 Emergency Power Unit (RAT + Fuel Cell + APU)

- Orientation is now part of the charge calculation.

- If a RAT is blocked by anything up to 2 meters in front of it the charge will be reduced.

- Added a graphing function for power curves so they are easier to compare.

- 1.0.5 Compatibility (Fix thrust reverser exhaust damage prevention).

[Svm420]

Hey I had a crazy idea that is in a similar principle to the thrust reverser. I was reading about the x-31 test plane NASA flew. The interesting thing about the jet is it uses a non thrust vectoring nozzle engine, but has thrust vectoring capabilities through the use of three plates on the sides of the engine that redirect the exhaust.

Thus giving it the ability to redirect thrust. Here is my question is it feasible to make a part or parts that can be attached to a engine to give it thrust vectoring? More advanced could it have independent control variance for the pitch and yaw. Like this having a deflection angle and percent of that angle to be used. Hope that makes sense.

Thought more about it and maybe somehow it just being a part that functions exactly as the gimbal module would be the simplest form.

Edited November 14, 2015 by Svm420

[satnet]

[quote name='Svm420']Hey I had a crazy idea that is in a similar principle to the thrust reverser. I was reading about the x-31 test plane NASA flew. ... Here is my question is it feasible to make a part or parts that can be attached to a engine to give it thrust vectoring? More advanced could it have independent control variance for the pitch and yaw. Like this having a deflection angle and percent of that angle to be used. Hope that makes sense. [URL]http://i.imgur.com/fCzoZ49.png[/URL]

Thought more about it and maybe somehow it just being a part that functions exactly as the gimbal module would be the simplest form.[/QUOTE]

It should be feasible. The plugin that adjusts the thrust would be pretty similar to the thrust reverser. I do see a few challenges though, so I'm not sure if/when I would be able to create it.

[Reiver]

[quote name='satnet']Uploaded version 0.11.

- Updated power curves by Reiver
- Mk3 Emergency Power Unit (RAT + Fuel Cell + APU)
- Orientation is now part of the charge calculation.
- If a RAT is blocked by anything up to 2 meters in front of it the charge will be reduced.
- Added a graphing function for power curves so they are easier to compare.
- 1.0.5 Compatibility (Fix thrust reverser exhaust damage prevention).[/QUOTE]
Fantastic :D

I'll have to fire it up this evening and check out these curves - with the new speed limits, I wonder if it'd be possible for the RAT-1 and RAT-360 to engage automatically if power fails and you're at a certain speed? Or for the RAT-1 not to need power to deploy? Such devices tend to be on emergency backup triggers, after all; by definition they're used when the power fails. ;)