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Author Topic: S-N stage Planning Thread  (Read 9784 times)
Graham2001
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« on: May 09, 2009, 06:13:42 AM »

I'm starting a new thread to cover the planning for the eventual creation of a NERVA stage for use with NASSP. (Click here for the documentation thread).

After going through the documentation I have collected over the past few months, the best candidates are both from 1961, as the documentation is probably detailed enough to allow development.

We have the two designs created by Martin (54,500lb or 80,900lb thrust) or the single design created by Douglas (75,000lb thrust).

I'm wondering if it would be possible to use the code from the S-IVb as the basis for the NERVA stage, while I am not a coder myself I would be willing to attempt it if someone could explain just what variables would need to be altered.

Someone else would of course have to handle the meshing and the textures.
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movieman
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« Reply #1 on: May 09, 2009, 02:02:46 PM »

The basics are pretty simple: just change the thrust and ISP. Where it gets more complex is in modelling things like the cooldown period after an engine burn, and obviously you'd need to change various bits of code that set up the J2 engine to use the NERVA engine instead (e.g. the nozzle positions are different).
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Graham2001
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« Reply #2 on: May 11, 2009, 07:34:10 PM »

The basics are pretty simple: just change the thrust and ISP. Where it gets more complex is in modelling things like the cooldown period after an engine burn, and obviously you'd need to change various bits of code that set up the J2 engine to use the NERVA engine instead (e.g. the nozzle positions are different).


It looks like I'll be modelling the 'Production (29m (94ft))' Martin NERVA design, as I have located both thrust and Specific Impluse (lsp). Once I have a copy of the source code I plan a 'quick edit' on the S-IVb code to implement the basic thrust/lsp/fuel load changes, which should allow for a test of the stage 'in orbit' with a CSM/LM attached.

Modelling the appearance of the stage brings up another issue, aside from the engine changes, this stage is taller than the S-IVb (29m (94ft) vs 17.8m(58.3ft)), we might need to consider implementing LC-39c with a taller launch tower to handle these vehicles.

The Martin design (at least in the documentation I have at present) did not provide for a restart capability. So the cooldown issue can be left aside for the moment.

Diagrams I have are not scaled, but do include body stations etc. Am trying to estimate position of engine nozzle from that.

Below are the estimated stats for the 'Production' NERVA stage (which I've dubbed the S-Nb) compared with those for the S-IVb (obtained from the Encyclopedia Astronautica).

S-IVb (1967)
Gross Mass: 119,900 kg (264,300 lb). 
Empty Mass: 13,300 kg (29,300 lb). 
Thrust (vac): 1,031.600 kN (231,913 lbf).
Isp: 421 sec.
Diameter: 6.60M (21.60 FT)
Span: 6.60M (21.60 FT).
Length: 17.80 m (58.30 ft).
Propellants: Lox/LH2.
No Engines: 1.
Engine: J-2.

S-Nb (1961, Martin)
Gross Mass: 50,000 kg (110,560 lb). 
Empty Mass: 9,300 kg (20,560 lb). 
Thrust (vac):  360 kN (80,900 lbf).
Isp:  809 sec.
Diameter: 6.60M (21.60 FT)
Span: 6.60M (21.60 FT).
Length: 29 m (94 ft).
Propellants: Nuclear/LH2
No Engines: 1.
Engine: 1500MW NERVA.
« Last Edit: May 12, 2009, 11:37:26 PM by Graham2001 » Logged
Graham2001
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« Reply #3 on: May 12, 2009, 08:37:16 PM »

The 'quick edit' has been completed. This is just an S-IVb with a changed thrust, lsp & empty mass. I've left the fuel amount unchanged as I'm uncertain how the number used in the S-IVb code was derived.

Attached below is a copy (snbx.txt) of the 'quick edit' code which I do not plan to commit to the CVS at this time as I have not yet compiled this to see if it will work in this form.

* snbx.txt (53.9 KB - downloaded 322 times.)
« Last Edit: May 12, 2009, 11:38:11 PM by Graham2001 » Logged
bluespace88
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« Reply #4 on: May 12, 2009, 08:59:13 PM »

Well, if you only changed those numbers, it should compile fine. 

I'm looking forward to seeing the progress of the NERVA stage  Thumbs Up
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Graham2001
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« Reply #5 on: May 12, 2009, 11:45:44 PM »

Well, if you only changed those numbers, it should compile fine. 

I'm looking forward to seeing the progress of the NERVA stage  Thumbs Up

Thanks, let me know how it goes,

Issues that will have to be resolved are:

1. Interface with the CSM as I am sure it would have been different from the interface with the S-IVb.

2. Removing the ability to have a docking tube as this stage would never have been suitable for an OWS.

3. Modelling the NERVA drive and it's peculiarities.

4. Preparing appropriate meshes (see my earlier posts), as the existing textures should cover the basic color schemes. (Is there anyone on forum with time free who'd wish to take a stab at doing this?) I've attached three pictures from the source document showing:

A. The S-Nb engine compartment.

B. The Saturn II/N launch vehicle (Would have been used for the Saturn Ib/V if it had been created)

C. The S-Nb stage

All pictures are best available.

Assuming the compiling works I'll write up a config file/in orbit scenario and attach it to this post.


* SNbNERVA.png (112.43 KB, 1059x826 - viewed 545 times.)

* SaturnIIN.png (91.4 KB, 1196x830 - viewed 505 times.)

* SNb.png (79.12 KB, 1137x849 - viewed 563 times.)
« Last Edit: May 13, 2009, 07:08:42 PM by Graham2001 » Logged
Graham2001
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« Reply #6 on: May 14, 2009, 08:20:10 AM »

Well, if you only changed those numbers, it should compile fine. 

I'm looking forward to seeing the progress of the NERVA stage  Thumbs Up

For some reason the  attempt to compile the code has failed.

Not sure why. I'm posting the error message below in html form. Hopefully someone with more experience at C++ coding/compiling can point out the mistake.

* BuildLog.htm (98.78 KB - downloaded 244 times.)
« Last Edit: May 15, 2009, 04:58:42 PM by Graham2001 » Logged
Graham2001
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« Reply #7 on: June 04, 2009, 09:15:25 AM »

For some reason the  attempt to compile the code has failed.

Not sure why. I'm posting the error message below in html form. Hopefully someone with more experience at C++ coding/compiling can point out the mistake.

Any ideas what I did wrong?
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Tschachim
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« Reply #8 on: June 04, 2009, 09:22:58 AM »

I don't have VS 2008 so I'm just guessing here, but it looks like you didn't set the include path to Orbitersdk/include properly: http://www.orbiterwiki.org/wiki/Free_Compiler_Setup#Include_path

Cheers
Tschachim
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Graham2001
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« Reply #9 on: June 06, 2009, 10:15:27 AM »

I'll redo that then. Might also restart the coding in case I caused any mistakes there.
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movieman
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« Reply #10 on: June 06, 2009, 11:49:09 PM »

BTW, you should be able to simulate this at a basic level without changing the code. Things like ISP and thrust can be configured in the scenario file:

I3V 7936.3
T3V 360000.0
S4EMPTYMASS 13300.0
S4FUELMASS 40700.0

That should work for trajectory testing.

Note that's for the Saturn V, you might need different settings for the Saturn 1b.
« Last Edit: June 07, 2009, 12:38:44 AM by movieman » Logged
Graham2001
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« Reply #11 on: September 28, 2009, 03:49:20 AM »

I'm planning on coming back to this shortly. Hope to have some working code ready for testing.

But in the meantime I spotted the picture below on a blog came from a report to congress on the NERVA program. (I've included a link only as the picture is rather large.).

http://up-ship.com/blog/wp-content/uploads/2009/09/nerva2.jpg

Note, this is the NERVA 2 design which would have (if my calculations are correct) about the same thrust as a S-IVb stage.
« Last Edit: October 02, 2009, 09:02:31 PM by Graham2001 » Logged
Graham2001
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« Reply #12 on: October 03, 2009, 06:30:22 AM »

BTW, you should be able to simulate this at a basic level without changing the code. Things like ISP and thrust can be configured in the scenario file:

I3V 7936.3
T3V 360000.0
S4EMPTYMASS 13300.0
S4FUELMASS 40700.0

That should work for trajectory testing.

Note that's for the Saturn V, you might need different settings for the Saturn 1b.

I'd just like to confirm that those settings will simulate the thrust/ISP of the S-N for the testing.

Still trying to create a dll using a 'minimum change' version of the S-IVb code and I still get a mess of errors.

I've attached a copy of the debugging log from the last attempt, if anyone can tell me what I've done wrong, please feel free to do so.

I've very quickly run up a pair of testing scenarios. Both use the same setup regards launch time/azimuth/target altitude. The only difference is that one incorporates the changes suggested by Movieman.

I'm having problems with my Orbiter installation at the moment and may need to re-install. I encourage anyone who tries these to report the results.

The important thing to remember here is that the NERVA stage being simulated has a thrust similar to an S-IV stage but a much higher fuel efficiency.

What I'd most like to see is information on just how long it took to reach orbit and how much fuel was left in the stage when you get there.

* BuildLog.htm (86.78 KB - downloaded 257 times.)
* AAP - Saturn V - Baseline.scn (1.14 KB - downloaded 247 times.)
* AAP - Saturn V - SIVn Stage.scn (1.19 KB - downloaded 262 times.)
« Last Edit: October 03, 2009, 08:09:47 AM by Graham2001 » Logged
movieman
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« Reply #13 on: October 04, 2009, 12:15:30 AM »

I'd just like to confirm that those settings will simulate the thrust/ISP of the S-N for the testing.

Yes.
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Graham2001
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« Reply #14 on: October 04, 2009, 06:27:46 AM »

I'd just like to confirm that those settings will simulate the thrust/ISP of the S-N for the testing.

Yes.


Thanks, now, as soon as I can figure out why Orbiter is freezing every time the Saturn V reaches launch I'll be right into trajectory verification. I'm going to set up a clean version using the modules previous to the current set. My PCs CPU might be having trouble with the threading.
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