Shadow shield for NTR

[Temstar]

People have been repeatedly asking for nerf to the Nerv atomic rocket motor since it was first introduced and it has indeed been nerfed from it's pre-1.0 days by increasing the mass from 2.25 tons to 3 tons. It now has a much worse TWR than its real life equivalent.

At the end of the day the Nerv is a solid core nuclear thermal rocket and no amount of nerfing will make chemical engines competitive to it over interplanetary trips unless you take away the fundamental qualities that differentiate it from chemical rockets. Instead of any further nerf I say decrease Nerv's weight back to previous level but simulate one aspect of NTR that make then truly different from chemical engines - the deadly radiation coming from the unshielded reactor.

First of all, I propose a 300m stand off distance from a fired NTR engine (unfired engines are pretty safe). Any kerbal with in this distance will immediately suffer the effects of acute radiation poisoning - pilots/scientist/engineers all lose their primary function, cannot EVA and cannot transfer (so basically, like tourists that can't be transferred), their IVA portraits should also show them unconscious inside their IVA suits and flickers of static on their screens..

Once they leave this hot zone, kerbals return to normal on account of kerbals having much higher tolerance to radiation than humans. However on their personal log (the thing in Astronaut Complex that says "Orbit around Kerbin", "Landed on Mun" etc) there will be a new "radiation sickness" entry. This flag doesn't have any material effect on the kerbal, rather it's just a reminder that you weren't as careful as you could have been with the crew.

Now to mitigate the effects of radiation coming from the reactor we need shadow shields:


Basically it's a flat, curved part similar to a heat shield but thicker. It comes in 1.25m, 2.5m and 3.75m size. When attached to the top of the Nerv it produces a cone area above the engine that is shielded from the radiation. At launch the shield is the same size as the stack but once in orbit you can toggle to extend the shield and the shield will have several lobes that slide out to expand the protected cone area to perhaps 90 degrees. It should weight a bit, so that a unnerfed 2.25 ton Nerv + shadow shield works out to be about the same weight as we have now, say 0.75 ton for 1.25m shield, 2.25 ton for 2.5m and 4.5 ton for 3.75m.

Docking a manned craft to the nuke stage will then have to be done with some care as you will have to approach the stage front on and stay with in the shadow. Similarly when undocking you will want to back the two crafts away from each other till then are more than 300m apart before you flip the nuke stage around.

The aim of this is to make NTR engines unwieldy enough that some thought needs to go into a vessel using one, yet to make the drawback not so punishing that no one will want to use them, and simulate this drawback in a way that it's unique to this type of engine.

Edited January 10, 2016 by Temstar

[tater]

I already only use nukes in a way that fists this description (i.e.: I copy NASA reference mission designs to a large extent). I always assumed the shield was included. Interesting idea, though, and one I agree with (I'm always creeped out by "tractor" designs I see here using nukes).

[pandaman]

Nice thinking Temstar.

I think some sort of distance warning would be helpful.  Maybe the 'danger area' could be linked to the number of nukes present and the amount of radiation also varies with distance.  A Geiger counter type function (part?) could be used to warn of the level of radiation present.

[Temstar]

Yeah some proximity warning is probably good idea. I wouldn't go as far as doing neutron flux calculation with multiple engines or anything complex like that though, that's probably too much for a game.

It's actually a pain in the ass if you do want to put more than one nuke engine on a ship - besides shadow shield they have to be carefully shielded from each other since you control the reactor activity by adjusting how much neutron is bouncing inside via control rods and you definitely don't want excess neutron from the other engine getting inside and causing unwanted fission.

[KrazyKrl]

This shielding argument has been discussed ad-nauseum since the introduction of the NERVA. Adding radiation doesn't add anything to gameplay, other than ship bloat.

On 11/22/2015 at 7:48 PM, juanml82 said:

As for radiation shielding, it's sort of "add cpu cycles to cause damage, add more cpu damage to reduce damage, end up where you started but with a performance hit"

 

A rep loss due to losing a used NERVA would be plenty. Anything more along the lines of a radiation-shadowing and radiation sickness life-support subsystem doesn't seem fitting in unmodded KSP. I don't see anything "fun" about needing to mess around with radiation shadow shields. What does this add to gameplay?

[Temstar]

4 minutes ago, KrazyKrl said:

I don't see anything "fun" about needing to mess around with radiation shadow shields. What does this add to gameplay?

I do, It actually makes a material difference on how you would use a NTR rather than what we have now where NTR is basically a chemical engine with higher Isp, lower thrust and runs on LF.

It's also a way to arrange a drawback for nuclear powered engines, rather than endlessly nerfing Nerv's performance to make it "fair" next to chemical rockets.

Edited January 11, 2016 by Temstar

[KrazyKrl]

1 hour ago, Temstar said:

I do, It actually makes a material difference on how you would use a NTR rather than what we have now where NTR is basically a chemical engine with higher Isp, lower thrust and runs on LF.

It's also a way to arrange a drawback for nuclear powered engines, rather than endlessly nerfing Nerv's performance to make it "fair" next to chemical rockets.

 

The NERV is already quite balanced. It has a high dry weight, very low TWR, weird form-factor, no gimbal, and very horrible atmospheric ISP. Making a rocket is easy, making an efficient rocket is hard. Just because the NERV has 800s ISP, doesn't mean that it's even outside of the envelope for realistically usable engines in KSP.

A whole radiation shielding system for literally one part doesn't sound like a reasonable use of game developer time.

Edited January 11, 2016 by KrazyKrl

[tater]

I think that limitations on where/how you can use a NERVA add a lot, actually. Trade-offs are exactly the kind of design decisions that make things interesting. 

[Temstar]

I'm not saying Nerv is not useful, on the contrary I would argue that Nerv is too versatile at the moment despite the 1.0 TWR nerf. Once I have access to the Nerv almost all of my big spacecrafts, weather that's interplanetary motherhship, or reusable Mun lander or deep space probes use it. Outside of edge cases like Tylo lander (where you need TWR), low Kerbol orbit probe (where abundant energy makes ion practical) Nerv becomes a no brainer once you get it. In particular having landers where the crew has to crawl around the bottom of the craft around the NTR engines doesn't sit well with me. That and as @tater said, tractor designs.
 

10 minutes ago, KrazyKrl said:

A whole radiation shielding system for literally one part doesn't sound like a reasonable use of game developer time.

This seems like it's just begging for the response "make more nuclear engines". Of course I'm not saying stock KSP should be all Orion drive and Nuclear Salt Water Rocket, but small stuff like radioisotope rocket or even space based reactor for power generation would be welcome.

[HafCoJoe]

11 hours ago, tater said:

Interesting idea, though, and one I agree with (I'm always creeped out by "tractor" designs I see here using nukes).

https://www.youtube.com/watch?v=kX7eds4Th14

[Bill Zarr]

If you look at any schematics for NERVA engines you can see that the shadow shield is built into the top of the reactor pressure vessel. Removing this then adding a part to add it back in is just pointlessly adding to the part count. And it ignores that the engine plumbing thingamabobs are actually above the shadow shield - do we get a new part for that too? 3 parts to build the 1 engine. I think having engines made of multiple parts might just be overcomplicating things a tad.

Radiation might be interesting of mechanic for a few people, but most people might just find it a pain in the rear and avoid using the engine altogether. The main effect it has is to make docking more complicated & tedious. I can't see that being a popular change. ISRU mitigates disadvantages chemical rockets have for interplanetary trips anyway. Preventing people from using puller designs without fixing the wobbliness that makes people resort to them in the first place probably isn't ideal either.

Then there's another layer of physics calculations that would need to be added in and done on every craft, because people would want to use fuel tanks & parts as shielding. Though if someone buys me a new computer I'm fine with this.

The LV-N  has already been nerfed repeatedly below what it's performance should be if it were a direct analogue of an NTR. Giving it another brutal pounding with the nerf bat seems counter productive. I guess some people just want to nerf this engine to the point it's unusable.

 

[Captain Sierra]

NTR tractors? I got one better than NTR tractors.

While intended as a puller, you're dealing with hot plasma on one end, deadly radiation on the other.  There's nothing safe about this.

[SpaceplaneAddict]

Two parts for the same performance of one part! Alright, count me in...!

 

No, seriously, The Nuke sucks enough now, why limit more of our currently decent designs? Not to mention drag induced by the shield, making it impossible for my Blade, as an example, to make orbit with the Delta-V it needs. 

 

What the nuke needs, is absolutely nothing. It's literaly perfect right where it is, no need to change it, IMO, Gameplay over (minor) realism anyday

Edited January 11, 2016 by SpaceplaneAddict

[Temstar]

I want to emphasis: the goal of this is not to nerf Nerv, in fact I would say if this radiation thing is implemented then Nerv is due for a buff, move the weight back to 2.25ton for a start. In fact it wouldn't be a bad idea to buff the Nerv to close to its real life NERVA counterpart.

The shield wouldn't increase drag, as you would only deploy the shield to wide angle once you're in space. In real life the shield is only deployed when the engine is idling since the radiation flux will be much lower. The real life shadow shield must be in the retracted state when the engine is firing to give adequate protection. We won't bother with that detail in KSP.

Lastly if you really want, there's always the possibility of designing your ship so that your crewed section is more than 300m away from the engine, weather that's in pusher or tractor configuration. In the extreme case where you just don't care about radiation sickness you can just run shield-less and rely on probe core. Per my suggestion there's no adverse effect except the "radiation sickness" flag on your kerbalnauts.

[tater]

You can also assume the shield is part of the basic part, but with the geometry as it is in terms of shielding (directionally). Then any added parts are to allow the NTR closer to the crew compartment if you need the solid angle.

[pizzaoverhead]

Nice idea! As an added effect, the NASA documentation discusses keeping the radiation away from non-crewed parts also due to degradation of material strengths. As stock KSP doesn't use probabilistic events for system failures such as fuel tank leaks, the joint strength between irradiated parts could be reduced over long periods of time (e.g. a Jool transfer).

22 hours ago, pandaman said:

I think some sort of distance warning would be helpful.  Maybe the 'danger area' could be linked to the number of nukes present and the amount of radiation also varies with distance.  A Geiger counter type function (part?) could be used to warn of the level of radiation present.

A Geiger counter sound and screen fuzziness is the traditional game way that's achieved. It could add a lot of atmosphere to EVAs.

18 hours ago, KrazyKrl said:

A whole radiation shielding system for literally one part doesn't sound like a reasonable use of game developer time.

This sounds less like a single part system, and more of an entirely new one, like the thermal system that was recently added. Radiation, both from man-made and natural sources is a huge part of space exploration. This could be one small part of a system dealing with all sources of radiation, such as solar flares and Van Allen belts. Given that radiation is one of the biggest issues with permanent off-Earth habitation, it makes sense to include some sort of radiation system in KSP.

18 hours ago, tater said:

I think that limitations on where/how you can use a NERVA add a lot, actually. Trade-offs are exactly the kind of design decisions that make things interesting. 

This is it exactly. Gameplay comes from overcoming challenges. Coming up with appropriate challenges that lead to interesting and varied choices through minimal added complexity is the goal.

16 hours ago, Bill Zarr said:

If you look at any schematics for NERVA engines you can see that the shadow shield is built into the top of the reactor pressure vessel. Removing this then adding a part to add it back in is just pointlessly adding to the part count. And it ignores that the engine plumbing thingamabobs are actually above the shadow shield - do we get a new part for that too? 3 parts to build the 1 engine. I think having engines made of multiple parts might just be overcomplicating things a tad.

Radiation might be interesting of mechanic for a few people, but most people might just find it a pain in the rear and avoid using the engine altogether. The main effect it has is to make docking more complicated & tedious. I can't see that being a popular change. ISRU mitigates disadvantages chemical rockets have for interplanetary trips anyway. Preventing people from using puller designs without fixing the wobbliness that makes people resort to them in the first place probably isn't ideal either.

Then there's another layer of physics calculations that would need to be added in and done on every craft, because people would want to use fuel tanks & parts as shielding. Though if someone buys me a new computer I'm fine with this.

The LV-N  has already been nerfed repeatedly below what it's performance should be if it were a direct analogue of an NTR. Giving it another brutal pounding with the nerf bat seems counter productive. I guess some people just want to nerf this engine to the point it's unusable.

 

There is no reason that the LV-N part can't have a retractable shadow shield built into it, with extra shielding available to allow more design flexibility. Much of what you've said about radiation could also be said of the thermal system which has added another layer of depth and gameplay to mission design. With regards to the LV-N being nerfed repeatedly below what it's performance should be, this could be undone if a radiation system allowed it to be balanced with similar challenges to those faced in real life.

15 hours ago, SpaceplaneAddict said:

No, seriously, The Nuke sucks enough now, why limit more of our currently decent designs? Not to mention drag induced by the shield, making it impossible for my Blade, as an example, to make orbit with the Delta-V it needs.

As tater said above, have the shield built-in to the part, with extra shields available for protection against non-LV-N radiation and for design freedom. This is how the shield in Temstar's image works. It's also retractable to reduce drag to a minimum.

[lajoswinkler]

Yes, this has potential. It has been suggested before, too. I like the idea of a kerbal health bar that gets depleted, and inverse square law of exposure to ionizing rays. Acute sickness is enough, no need for chronical thingies.

[tater]

FWIW I always put heavy RCS for braking on my NTR tugs, and I never point them at the craft I am rendezvousing with, and within a km or so I keep the target directly in front. I like the logistic challenge, vs treating it just like any other engine.

[Hannu2]

This would be realistic, but not entertaining way. It would not be difficult to learn, but just laborious and time consuming to execute every time. In real world there are very large safety margins to avoid collisions even they do not have nervas. It takes several orbits (hours, even days) to rendezvous and dock a spacecraft to a station. Would executing of such procedures (by hand or automatically) really give some value to game? At least I do not like this kind of time consuming piloting tasks or any other kerbal work activities. This could be a mod for them who like this kind of piloting but I do not want it to be stock.

[Hannu2]

On 11.1.2016 at 5:06 AM, Temstar said:

I'm not saying Nerv is not useful, on the contrary I would argue that Nerv is too versatile at the moment despite the 1.0 TWR nerf. Once I have access to the Nerv almost all of my big spacecrafts, weather that's interplanetary motherhship, or reusable Mun lander or deep space probes use it. Outside of edge cases like Tylo lander (where you need TWR), low Kerbol orbit probe (where abundant energy makes ion practical) Nerv becomes a no brainer once you get it. In particular having landers where the crew has to crawl around the bottom of the craft around the NTR engines doesn't sit well with me. That and as @tater said, tractor designs.

Is it right or realistic to make laziness of player a true reason of choosing chemical engine instead of nuclear? It is always possible to use rendezvous trajectory on which there are not problems. It is not very difficult technically, but just laborious, time consuming and boring task to repeat every time when two ships dock.

I think than LV-N is now quite well balanced, at least with stock fuel switch mod. It is a workhorse, actually only practical solution, for medium and heavy interplanetary use. I never use it in landers. I could but other engines are more practical. It is very unrealistic but realistic performance would not fit in small solar system and KSP's idea to demand near low energy transfers between planets.

Tractor designs are also practical solution to inaccuracy of game physics and lack of proper control systems. In real world there would not be a problem to make rigid ship or active stabilizing or use very low thrusts, even burn times of years. But such things would need better physics and control systems in the game. I think that there are many things which gives "more bang for the buck" (also in realism sense) than program such very technical and expensive details just to move feasible position of engines from front of the ship to back.

[Temstar]

Tractor design is used both in real life and in ksp to reduce vehicle mass, since most materials are stronger in tension than compression. Tractor design allows extremely long spacecrafts to be low mass, and one design such "waterski" crafts (eg ISV Venture Star) precisely so that the crew section can be as far away from the deadly engines as possible because of radiation.

I disagree that requiring thought at design time and some careful flying at docking time is laborious. And if one is of the opinion that the radiation simulation is unnecessary then you still have the option of not using the shadow shield part, put probe core on ships, enjoy the higher TWR and just ignore the radiation sickness flag. I deliberately proposed a system to not kill crew or leave them with any permanent damage to leave that opt out option open.

[Champ]

On 11/1/2016 at 4:06 AM, Temstar said:

I'm not saying Nerv is not useful, on the contrary I would argue that Nerv is too versatile at the moment despite the 1.0 TWR nerf. Once I have access to the Nerv almost all of my big spacecrafts, weather that's interplanetary motherhship, or reusable Mun lander or deep space probes use it. Outside of edge cases like Tylo lander (where you need TWR), low Kerbol orbit probe (where abundant energy makes ion practical) Nerv becomes a no brainer once you get it.

 

Sorry, but i think you are wrong : it is much simpler, cost-effective and easier to use chemical rocket engines when going to Duna or Eve (not talking about landing where TWR is an issue). Of course, you can go there with NERV, but it will cost more and be more painfull (long burn time) than it would be with a chemical engine. There are many (really, many) situations where a NERV can do the job, but a chemical engine can do it better.

 

On 10/1/2016 at 3:28 AM, Temstar said:

First of all, I propose a 300m stand off distance from a fired NTR engine (unfired engines are pretty safe).

I think I read somewhere on this forum that this is wrong : NERV is less dangerous when firing than when not firing.

 

BTW, I would love to see radiations included in the game, but not as you describe it.

I don't care about radiation from the NERV engines : anything that goes beyond LKO (for example, to the Mün) will run throuh VanAllen's belts, so it needs heavy radiation shielding, NERV engines or not.

I think we could have a checkbox on every crew-containing part (hitchhiker's module, pods, cans, cockpits, cupola) to specify if we want it to be radiation-shielded. If checked, it adds weight to the part. If not, then going through VanAllen's belt (or using NERV) should kill all crew.

That way, you can have lightweight non-shielded crew parts (for when you don't want to go beyond LKO - usefull for SSTO spaceplanes, for example, or in early-carrier) or heavy shielded crew parts (for when you want to go farther : mun, minmus, or any other planet).

We could even have a slider to configure the radiation shield : a ship that is going to explore the Jool system should have a heavier shield than a ship that is just going to the Mün

[radonek]

I, for one, would be happy to give this a try. As a mod. But I see no reason for it to be stock. It's a lot of work for developers for some incomprehensible aproximation. It does not acount for backscatter, material differences in shielding, material defects etc. I agree it would be nice to balance LV-N other way then just adding weight (like thermal mechanic did), but this is lots of work for little improvement.

[SpaceplaneAddict]

19 hours ago, pizzaoverhead said:

As tater said above, have the shield built-in to the part, with extra shields available for protection against non-LV-N radiation and for design freedom. This is how the shield in Temstar's image works. It's also retractable to reduce drag to a minimum.

But, you see, I have to run the nuke at 20km up to support the failing RAPIERS, meaning I would have to dagr the shield o0-en

[pizzaoverhead]

3 minutes ago, SpaceplaneAddict said:

But, you see, I have to run the nuke at 20km up to support the failing RAPIERS, meaning I would have to dagr the shield o0-en

Check out the picture in the first post. The deployable shield isn't for when the engine's running; there's a fixed shield in the top of the LV-N for that. The retractable shield is for providing even more safe space while on orbit, for attaching tanks, doing EVAs, docking, that kind of thing. Here's what the shielded area on the first post's craft looks like without the shield deployed for comparison:

You can read more here: http://www.projectrho.com/public_html/rocket/radiation.php