Project NASA Viking

[Buck Rogers]

I've resurrected the Viking project
I think I've managed to salvage enough to finish it.



Currently doing the flight plan for Viking1, and then there's Viking2...

 

[Buck Rogers]

Progress is going "better" than expected, even after a complete rework of the .cfgs, and I've finally managed to make a trajectory matching the historical dates (Viking1).

As this is a historical mission I've tried to painstakingly research every little detail. One detail still evades me and unfortuneately seems critical; and the resulting demise of the Orbiter mission.
I know that the Orbiter had a fuel mass of 1445kg, both propellant and attitude rcs. The nitrogen rcs has a low ISP of ~730 and the mission was ended due to rcs depletion. Having an accurate figure for the rcs fuel mass would be paramount for a historical representation.
If anyone has any details on this (or even any other aspects of the flight- there's still a lot of guess work, initial orbit inc. etc.) it would be very much appreciated

Here's a picture of Mars orbit insertion, ~40 min burn.

 

[Urwumpe]

Didn't it have cold gas attitude control, based on compressed nitrogen? If you know the tank size and other details, it could be calculated how much "fuel mass" it has, until reaching regulator pressure.

 

[Buck Rogers]

Didn't it have cold gas attitude control, based on compressed nitrogen

Yes it did, have found an interesting paper on cold gas rcs, and some very detailed information on the lander, but info on the orbiter is scarce. It's supposed to have the same/similar bus to the late Mariner probes but there I just get the same minimal data and no further details on tanks etc. From the sketchy cut-aways I've seen the tanks look almost 50/50 in size (but must have 3 tanks because the main engine runs on a bi-propellant- all with different densities)? I started with 45kg rcs and it seems waively low, thinking 300kg might be closer?

 

[Thunder Chicken]

Yes it did, have found an interesting paper on cold gas rcs, and some very detailed information on the lander, but info on the orbiter is scarce. It's supposed to have the same/similar bus to the late Mariner probes but there I just get the same minimal data and no further details on tanks etc. From the sketchy cut-aways I've seen the tanks look almost 50/50 in size (but must have 3 tanks because the main engine runs on a bi-propellant- all with different densities)? I started with 45kg rcs and it seems waively low, thinking 300kg might be closer?

Not sure how relevant this is to Viking, but this has some information on Mariner 1971 and it states that the system had 2.4 kg / 5.3 lbm of nitrogen gas for the ACS system.

Mariner Mars 1971 attitude control subsystem - NASA Technical Reports Server (NTRS)

The Mariner Mars 1971 attitude control subsystem (ACS) is discussed. It is comprised of a sun sensor set, a Canopus tracker, an inertial reference unit, two cold gas reaction control assemblies, two rocket engine gimbal actuators, and an attitude control electronics unit. The subsystem has the...

ntrs.nasa.gov

 

[Gondos]

From The autonomous viking:

Gas was one of the few expendable
items carried on the orbiters. Each
spacecraft started with about 31 pounds
of attitude control gas.

According to this the propulsion subsystem has the following characteristics :

Vacuum thrust 1334 N
Vacuum specific impulse 2857.6 N-sec/kg
Nominal N204 flow rate 0.280 kg/sec
Nominal MMH flow rate 0.186 kg/sec
Propellant load capacity 1423 kg
Usable propellant load 1405 kg
Minimum burn duration 0.4 sec
Shutdown impulse 9 to 53 N-sec

The difference between 1423kg and 1445kg is not quite 31 pounds, maybe the excess is from the helium pressurant?

 

[Gondos]

Definitive answer from Viking '75 spacecraft design and test summary. Volume 2: Orbiter design, page 188

The RCA used compressed nitrogen gas as the propellant. Each of the gas storage vessels held 7 kg
(15.5 ib) of gas when fully loaded at 30.3 MPa (4400 psig) and 37.8 ° C (i00 ° F).
The specific impulse is 68 sec at 20 ° C (68 ° F) and the jet thrust is 0.133 N
(0.03 Ib). The effective impulse expended for a 22-msec electrical pulse into
a pair of jet valves (minimum impulse bit) was 5.6 mN-sec (0.00126 ib-sec).
The distance from the roll axis to the jet valves on the ends of the solar
panels was 5 m (16.4 ft).

In line with the 31pounds mentionned above

 

[Buck Rogers]

Thank you everyone, your input has been very useful.
Interestingly the abstract in the https://arc.aiaa.org/doi/10.2514/6.1980-1173 states the exact burn time and Dv of the main engine (and no. of burns, 23), with this I can easily calibrate the the fuel mass (rcs is still a little confusing, AFAIK it had 3 interlinked systems) The results are very close, slightly better than "on paper" and a little more rcs than initially estimated.
The voyage continues...

 

[Luke Reichelt]

Looking good so far, but when are you going to resume your work on those Shadow vessels?

 

[Buck Rogers]

Added trees, fixed the launch site

 

[barrygolden]

Man thats way cool we need that in other addons

 

[barrygolden]

Just a thought when you release this you might do several SCN like the launch MOI, landing , and on the surface. You might get BrianJ to help with some of these

 

[Buck Rogers]

Just a thought when you release this you might do several SCN like the launch MOI, landing , and on the surface. You might get BrianJ to help with some of these

This is what I've mostly been doing the last few weeks, it's very time consuming and difficult, especially with minimal/conflicting info.
And BrianJ has been an inspiration for a long time

Actually all round it's looking pretty good, but still a lot to do, as well as documentation, but the data is coming together.
The Viking1 mission works through to MOI so far, I also want to include .scns for the extended Orbiter mission as well.
All major technical details are dealt with, exact replicated thruster arrangements etc. Both the Lander and Aeroshell have very special settups- your landing on 3 engines!
But there are still aerodynamics issues, the Lander, parachute etc. are good but entry is not optimal.

And started to work out the dependecies/credits (the project was on ice for several years).
Everything after the 2nd stage I've built from scratch with exception of the heatshield tex, which is modified from the Insight addon from @BrianJ (if I have your permission?), and of course the launchpad, which I can make a dependency for the excellent Osiris Rex addon.
But the Titan is a bit of a frankenmonster, has parts of mine, Multi-titans, and of CVELtitans (some parts are better) from @sputnik, which doesn't work in Orbiter2016, may I redistribute these parts?
Current status:

 

[BrianJ]

Everything after the 2nd stage I've built from scratch with exception of the heatshield tex, which is modified from the Insight addon from @BrianJ (if I have your permission?), and of course the launchpad, which I can make a dependency.......

Probably the heatshield tex I begged from Papyref (or was it Momo?) Well and NoMatter. I'm sure its fine to use it
Use/include/recycle any parts of my stuff that are useful to you.
Looks fabulous so far
Cheers,
Brian

 

[Buck Rogers]

That's great! Thanks a lot

 

[Buck Rogers]

A lot of hurdles but slowly making progress. Working on the landing site:
The small star in the sky is the Earth...

 

[Luke Reichelt]

I really hope Buck Rogers is simply busy with the Viking probe add-on and not on another 18 month hiatus, especially since there's still a lot of things that need to get done with regards to the whole B5 vessels project.

 

[Buck Rogers]

Wish it were so
Have had little capacity. So far it looks like VesselBuilder works with Orb2024, but this project really needs a coder (any takers?). Maybe when I have more time I can take a look at LUA for it?
And I'd just like to state for general information and future reference that if anyone wishes to use part of, expand on, or update any of my addons in the case of my future absense or inability please feel free to do so, just credit those involved (Orbiter wouldn't be what it is without the colaboration of so many), and especially those I've had the honour to work with I hope within there capacity that they can continue to update and improve on those and all things Orbiter. And of course I still intend to contribute and colaborate where I can.

A new Orbiter, a new dawn. Here's to a bright future! Happy Orbiting everybody!

 

[Urwumpe]

Wish it were so
Have had little capacity. So far it looks like VesselBuilder works with Orb2024, but this project really needs a coder (any takers?). Maybe when I have more time I can take a look at LUA for it?
And I'd just like to state for general information and future reference that if anyone wishes to use part of, expand on, or update any of my addons in the case of my future absense or inability please feel free to do so, just credit those involved (Orbiter wouldn't be what it is without the colaboration of so many), and especially those I've had the honour to work with I hope within there capacity that they can continue to update and improve on those and all things Orbiter. And of course I still intend to contribute and colaborate where I can.

A new Orbiter, a new dawn. Here's to a bright future! Happy Orbiting everybody!

For what do you need a coder there?

 

[Buck Rogers]

For what do you need a coder there?

At least for the aerodynamics, I broke my brainbutt trying to get something useable, VB doesn't have an input for drag coefficients (need to be able to define drag for a specific AOA) and tweaking the lift coef. etc. hasn't brought great results. VB works ok with Deltaglider and such but there are no working examples for a capsule, and maybe I'm still missing something.
But there are also other compromises that could be avoided if coded, the good news is that VB is great as a test bed for many features, all the required data for animations, stats etc. "just" needs to be transferred to new code, and fortuneately there are also several excellent capsule code examples available.
Now that one can do a lot of coding without compiling (LUA) maybe in the distant future I can get something up and running, but I can be far more productive doing what I'm better at, also there is still a lot to do, I was planning to do .scn files up to the end of service of the orbiter, and then for Viking2 as well (and to think back then when I started this project (a few years ago) my ambition was to update all the historic flights)!

With team work I think this project will see the light of day sooner.