Problem Aerodymamic rocket using multistage guidance - Orbiter-Forum

4throck · 07-09-2012, 10:56 AM

I need some advice on the best way to implement a two stage aerodynamic sounding rocket using multistage guidance. The rocket I'm trying to simulate is the VS-40 (http://en.wikipedia.org/wiki/VS-40).

Here it is in Orbiter:

As the rocket has no active control surfaces (besides fixed tail fins) and no RCS, it makes sense that the guidance is only used to set the initial launch attitude.

I think that the best way to do it would be to pitch to the real launch inclination (about 85º) at 0 seconds and issue no further commands.

But I know that the rocket fins induce a slow roll (about 2º second) so a roll command would also make sense.

I've tested some basic guidance files but I'm not happy with the results. I can force the desired heading OR roll during all the flight, but the rocket struggles to keep the attitude. If I only set the values initially, it gets into a spin almost immediately.

The meshes are centered on 0,0,0 and all diameters and engine parameters are according to the source values.

Any advice or add-ons that I can look into?

**Urwumpe** · 07-09-2012, 11:12 AM

Don't use Multistage.dll, but instead make your sounding rocket a DLL... it isn't the most complex kind of rocket and good for beginners in C++, since you don't have any guidance, only aerodynamics. Alternatively, use spacecraft3.dll and attachments.

4throck · 07-09-2012, 11:44 AM

The sc3 option is interesting...

As you know I'm more into meshes / textures than programing, so I only need a way to get a generic prototype into Orbiter.
As for custom .dll, it is being discussed on the Portuguese speaking forum and someone else may do it, time permitting, but based on the sc3 / multistage.

This development method works and is simpler for the programmer, otherwise the same person will have to code AND research.
I find it is much simpler to have the mesher do the research (not only of reference photos but also of mission profiles, payloads, trajectories, etc.).

**Urwumpe** · 07-09-2012, 11:54 AM

Quote:

Originally Posted by 4throck

This development method works and is simpler for the programmer, otherwise the same person will have to code AND research.
I find it is much simpler to have the mesher do the research (not only of reference photos but also of mission profiles, payloads, trajectories, etc.).

Don't ever go into agile software development, before you are schizoprenic enough for it.

Well, something more serious: Don't forget that you are as mesher not knowing what information the programmer needs. A programmer can't give you the information, that you need for making the meshes. You can research together, in the same time, in one session, that can be very effective and I recommend it from my experiences.

You can in fact, program and mesh as the same single person, if you have the skills, but seriously: Not all do.

It is just a matter of your work pipeline. You could easily adapt "Kanban for SE" to "Kanban for Orbiter add-on development", to manage your development times and help you stay on track.

A good mesher will likely never become a good coder, just like a good coder will not become a good mesher in most cases, but still you can sometimes be "good enough for government work".

liber · 07-09-2012, 02:50 PM

If is 1st stage booster to set thruster visually change hight for thruster off and for the thruster width change diameter.
I don't think this change of value for multistage.dll effect flight dynamic,only engine power and rocket weight.

4throck · 07-09-2012, 03:46 PM

I already have the tower modeled, with the rocket configured to right height.
I know that I can "cheat" by rotating the mesh, but as I said before, someone else is going to tackle programing, so I don't mind that it looks funny. Also, (although I don't have any images of it right now) I have corrected the exhaust.

I only need some advice regarding multistage guidance (although of course I welcome your comments :-) )

07-09-2012, 10:56 AM	#1
4throck Enthusiast !	Aerodymamic rocket using multistage guidance I need some advice on the best way to implement a two stage aerodynamic sounding rocket using multistage guidance. The rocket I'm trying to simulate is the VS-40 (http://en.wikipedia.org/wiki/VS-40). Here it is in Orbiter: As the rocket has no active control surfaces (besides fixed tail fins) and no RCS, it makes sense that the guidance is only used to set the initial launch attitude. I think that the best way to do it would be to pitch to the real launch inclination (about 85º) at 0 seconds and issue no further commands. But I know that the rocket fins induce a slow roll (about 2º second) so a roll command would also make sense. I've tested some basic guidance files but I'm not happy with the results. I can force the desired heading OR roll during all the flight, but the rocket struggles to keep the attitude. If I only set the values initially, it gets into a spin almost immediately. The meshes are centered on 0,0,0 and all diameters and engine parameters are according to the source values. Any advice or add-ons that I can look into?

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07-09-2012, 11:12 AM	#2
Urwumpe Donator	Don't use Multistage.dll, but instead make your sounding rocket a DLL... it isn't the most complex kind of rocket and good for beginners in C++, since you don't have any guidance, only aerodynamics. Alternatively, use spacecraft3.dll and attachments.

07-09-2012, 11:44 AM	#3
4throck Enthusiast !	The sc3 option is interesting... As you know I'm more into meshes / textures than programing, so I only need a way to get a generic prototype into Orbiter. As for custom .dll, it is being discussed on the Portuguese speaking forum and someone else may do it, time permitting, but based on the sc3 / multistage. This development method works and is simpler for the programmer, otherwise the same person will have to code AND research. I find it is much simpler to have the mesher do the research (not only of reference photos but also of mission profiles, payloads, trajectories, etc.).

07-09-2012, 11:54 AM	#4
Urwumpe Donator	Quote: Originally Posted by 4throck This development method works and is simpler for the programmer, otherwise the same person will have to code AND research. I find it is much simpler to have the mesher do the research (not only of reference photos but also of mission profiles, payloads, trajectories, etc.). Don't ever go into agile software development, before you are schizoprenic enough for it. Well, something more serious: Don't forget that you are as mesher not knowing what information the programmer needs. A programmer can't give you the information, that you need for making the meshes. You can research together, in the same time, in one session, that can be very effective and I recommend it from my experiences. You can in fact, program and mesh as the same single person, if you have the skills, but seriously: Not all do. It is just a matter of your work pipeline. You could easily adapt "Kanban for SE" to "Kanban for Orbiter add-on development", to manage your development times and help you stay on track. A good mesher will likely never become a good coder, just like a good coder will not become a good mesher in most cases, but still you can sometimes be "good enough for government work".

07-09-2012, 02:50 PM	#5
liber Orbinaut	If is 1st stage booster to set thruster visually change hight for thruster off and for the thruster width change diameter. I don't think this change of value for multistage.dll effect flight dynamic,only engine power and rocket weight.

07-09-2012, 03:46 PM	#6
4throck Enthusiast !	I already have the tower modeled, with the rocket configured to right height. I know that I can "cheat" by rotating the mesh, but as I said before, someone else is going to tackle programing, so I don't mind that it looks funny. Also, (although I don't have any images of it right now) I have corrected the exhaust. I only need some advice regarding multistage guidance (although of course I welcome your comments :-) )