NASSP Custom PDI Scenarios for NASSP

[Tycho]

I've been running ad-hoc PDI scenarios in Orbiter 2016 using the AAPO LM from Orbiter 2010 (that works with some bugs in 2016), but was curious about setting up custom PDI scenarios (targeting different landing sites) in NASSP for 2016, as the uploader of the video below did. How might I go about creating such a scenario/where in the checklists would I have to start to tell the AGC where I'd like to land after aligning orbits, say if I'm starting with the Apollo 11 PDI scenario that comes with NASSP 8.0 Alpha? Thanks!

[ame="https://www.youtube.com/watch?v=PP-LzofxsKA"]Video I'm Referencing[/ame]

 

[indy91]

Hey, that's my video! The only way to create custom PDI scenarios is flying a whole mission to that point. Main reason is the Virtual AGC. There isn't really a practical way to edit the computer memory state so that the AGC is in the correct state for PDI. NASSP comes with a few tools to fly complete lunar landing missions. They require a lot of knowledge about Apollo trajectory planning and especially for custom landing sites it is quite tricky to use those tools. But it can be done. I can help you with that, if you want. We have a Mission Control feature which make this job much easier and lets you concentrate on being an astronaut instead of a flight controller. But that feature will not be available for custom missions and right now it only covers Apollo 7 and 8; Apollo 9-11 will be added in the next few months.

Eventually NASSP will probably have pre PDI scenarios for all the lunar landings. Main reason to not do this already is that we still are adding major subsystems to the LM. The Apollo 11 PDI scenario you mentioned is a good example. Since it was created the RCS propellant section was implemented. So with that scenario and the most recent NASSP 8.0 Alpha release you have to quickly configure the RCS from scratch. Fire the pyros for the explosive helium isolation valves, open a bunch of other RCS valves and all that very quickly before the PDI burn starts. Once the major subsystems are all implemented (fairly soon!) old scenarios won't become outdated so quickly and we will probably add some more scenarios that we will then keep updated. Right now keeping scenarios other than the launch scenarios updated would be more of a burden than any help.

 

[Tycho]

Hey, thanks for the reply (neat vid, by the way)! I suspected as much; there's quite a bit going on in the .scn files. I had a fleeting thought that it would be as simple as picking up post-DOI and punching some new coordinates into the DSKY before P63 or something, but if that were the case, then keeping the mid-mission scenarios updated wouldn't be quite so onerous now that I think about it. I'll probably mess with some launch scenarios and trajectory planning in 2010/2016, then. Any recommended reading materials for this? I reckon some of the original mission planning documents off ALSJ might be useful, but is there anything NASSP/Virtual AGC-specific you'd recommend? Thanks!

 

[indy91]

Hey, thanks for the reply (neat vid, by the way)! I suspected as much; there's quite a bit going on in the .scn files. I had a fleeting thought that it would be as simple as picking up post-DOI and punching some new coordinates into the DSKY before P63 or something, but if that were the case, then keeping the mid-mission scenarios updated wouldn't be quite so onerous now that I think about it.

The AGC absolutely lets you change the targeted landing site after DOI. But you are fairly constraint in your choice. The maximum recommended crossrange for PDI is 8 nautical miles, so you can't deviate much from your current orbit to the north or south. And in the downrange direction you are constraint by the altitude at PDI. Normally after DOI you have a 60NM apolune and 50,000 feet perilune orbit, with PDI planned at perilune. If you want to land further west or east you won't be at perilune for PDI. But this isn't a very hard constraint, you can certainly land +/- 100 NM downrange from the targeted landing site.

The main method of calculating all sorts of things for NASSP is the RTCC MFD, which is part of the NASSP releases. It should have everything you need to get you into the right position for PDI: calculations for midcourse corrections, lunar orbit insertion, descent orbit insertion and much more. You can find the manual in the NASSP releases under "Doc\Project Apollo - NASSP\Programmers Notes\ApolloRTCCMFD.pdf" The manual is a bit outdated, it covers the state of the MFD when NASSP 7.0 was released 10 months ago, so it is missing some important parts about DOI, PDI etc. But you might be able to click yourself through the MFD and figure out those features of the MFD without the help of the manual. The MFD has prepopulated numbers for most lunar landing missions. So if you e.g. load the MFD in an Apollo 11 scenario, it already has the Apollo 11 landing site saved as a mission constant.

Also helpful for new-ish users is the Checklist MFD. For Apollo 7-11 it already covers the whole mission, so it basically is a switch-by-switch guide for complete missions. It doesn't teach you anything about spacecraft systems etc. but it can help with not making too many user errors.

I'll probably mess with some launch scenarios and trajectory planning in 2010/2016, then. Any recommended reading materials for this? I reckon some of the original mission planning documents off ALSJ might be useful, but is there anything NASSP/Virtual AGC-specific you'd recommend? Thanks!

In terms of mission documentation there luckily is a lot available. The AFJ and ALSJ have many of the flight plans and checklists, just check the pages for a specific mission. NASSP has some generic checklists under "Doc\Project Apollo - NASSP\Word Checklists", but I always prefer to use the flown, mission specific checklists whenever they are available. The Apollo Operations Handbook for CSM (https://history.nasa.gov/afj/aohindex.html) and LM (https://www.hq.nasa.gov/alsj/LM10HandbookVol1.pdf) are also good reading material.

 

[Tycho]

Thanks! I knew the AGC gave some leeway, but I was thinking more about reprogramming a landing site into the computer after a drastic plane change (so AGS/PGNS don't think I'm targeting the same site from a different plane and thus throwing the att. control for a loop). I have some free time coming up and I think I'll be toying around with some hardcore custom Apollo mission planning in NASSP, so thanks for the suggestions/materials!

 

[indy91]

Thanks! I knew the AGC gave some leeway, but I was thinking more about reprogramming a landing site into the computer after a drastic plane change (so AGS/PGNS don't think I'm targeting the same site from a different plane and thus throwing the att. control for a loop). I have some free time coming up and I think I'll be toying around with some hardcore custom Apollo mission planning in NASSP, so thanks for the suggestions/materials!

The optimal way to fly to another landing site is by planning for it before LOI. A midcourse correction can (if you sacrifice free return) achieve a nice plane change with not too much DV. The second best option is during LOI. High latitudes on the Moon are always going to be difficult to reach, so e.g. the Apollo 15 LOI burn had a very large out-of-plane DV component (766.4 ft/s).

You pointed out my video where I landed at Tycho crater. Do you want to know how I got there? Badly. I started with an Apollo 14 post-TLI scenario and did midcourse corrections and LOI to get me into the highly inclined orbit needed to reach Tycho crater. I guess we don't have the best planning tools for such a mission yet, because LOI alone was 1000 ft/s more than usual. So I was able to get into the right orbit for this, but my CSM does not have enough propellant enough to fly back home. An Apollo mission to Tycho would need some major optimizations to be able to get back home, even in the real world. That starts basically with liftoff and TLI.

The MCC and LOI targeting of the RTCC MFD should be able to get you to most landing sites that are at less extreme latitudes than Tycho.

 

[Tycho]

Right. A major plane change post-LOI is a pretty savage way of doing it, but I was coming at it from the perspective of adapting an existing pre-PDI scenario into one targeting another site (which I gather is not possible b/c it really messes with the Virtual AGC, after having experimented with it). I'll definitely have to give it a shot the authentic way using RTCC. Are full landing missions flyable launch-to-lunar landing in NASSP 8.0 for 2016 yet, or do I have to transfer over a post-TLI scenario from 2010? (Sorry, haven't been following the dev threads).

 

[indy91]

Are full landing missions flyable launch-to-lunar landing in NASSP 8.0 for 2016 yet, or do I have to transfer over a post-TLI scenario from 2010? (Sorry, haven't been following the dev threads).

Yes, that is all possible in Orbiter 2016 now. We had some trouble with the new touchdown points feature for vessels and also the terrain at the launchpads for a while, so that made it necessary to use post-TLI scenarios from Orbiter 2010 to continue flying a mission in Orbiter 2016. But those issues are now solved.

About NASSP 8.0, it's probably the buggiest it will ever be right now, because the last major LM subsystems are being added. So CTDs and frequent new builds on Github are probably going to happen. But generally it is possible to fly a full mission all in Orbiter 2016.