Author Topic: Modelling Mars  (Read 108557 times)

Offline Nittany Tiger

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Re: Modelling Mars
« Reply #540 on: 03/11/2017 01:46 AM »
I stand corrected, and granted it's been a year since I've read the story, and I don't have a copy.  LH2 shielding was my first thought on as to why the accident wasn't considered plausible.  Furthermore, I know the accident created a propellant leak that would have vented the protective LH2 as time went on.

Honestly, this whole tragedy could have been avoided if the test was unmanned, but RL NASA sent pilots on the first space shuttle flight, and they do sometimes toss safety aside (which played roles in both RL space shuttle disasters), so it's not implausible for this to happen in the story.  Honestly, I never saw it as implausible except that I think NASA might have had more failsafes built into a test NERVA and fly it unmanned.

It's just hard to say.

Also, I meant to say "containment failure."  I missed that error.  What I was thinking about was an electronic failsafe that would turn the graphite moderators to a full position to try to shut down the core if temps exceeded a certain threshold (and a temp increase did precede the explosion IIRC).  Containment failure would be the NERVA shielding blowing and spreading radiation out.

I have a limited knowledge of NERVA and nuclear reactors, so I'm prone to make mistakes.

It would be interesting to model the radiation field of an exposed NERVA core.  IIRC, only part of the shielding was busted, and it busted out the side, so I wonder how the radiation would spread out.

« Last Edit: 03/11/2017 01:55 AM by Nittany Tiger »

Online Archibald

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Re: Modelling Mars
« Reply #541 on: 03/11/2017 02:14 PM »
There actually was an unmanned test that (of course) went perfectly. :(

The 1/72 scale Ranger is pretty cool, 1/72 was my favorite scale ten years ago (before I stopped modeling)

I wish there could be a Big Gemini add-on either in Kerbal or Orbiter. If anybody can help :p

ETS and my own TL Explorers started exactly the same  premise (entirely coincidentally) but they are entirely different. Ranulf, how is your TL going ?
« Last Edit: 03/12/2017 09:40 AM by Archibald »

Online brickmack

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Re: Modelling Mars
« Reply #542 on: 03/12/2017 02:03 AM »
There actually was an unmanned test that (of course) went perfectly. :(

The 1/72 scale Ranger is pretty cool, 1/72 was my favorite scale ten years ago (before I stopped modeling)

I wish there could be a Big Gemini add-on either in Kerbal or Orbiter. If anybody can help :p

ETS and my own TL Explorers started exactly the same  premise (coincidentally) but they are entirely different. Ranulf, how is your TL going ?

Big Gemini is included in FASA for KSP (along with several other Gemini-derivatives) and is compatible with Realism Overhaul too

Online Archibald

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Re: Modelling Mars
« Reply #543 on: 03/12/2017 09:39 AM »
very cool. What is FASA ?

Online brickmack

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Offline Nittany Tiger

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Re: Modelling Mars
« Reply #545 on: 03/14/2017 05:31 PM »
Yeah, FASA has Big Gemini, MOL, the Saturn C-8, the M-1, and the 156" UA SRBs for any Saturn MLV you want to make.  It doesn't have stretched S-I, S-II, or S-IVB stages, but you can install procedural parts and add the stretching yourself.

Frizzank isn't working on FASA anymore, but I think someone else is updating it for people who want to use it in Real Solar System + Realism Overhaul installs.  You can get a stock version from them as well.

Offline Nittany Tiger

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Re: Modelling Mars
« Reply #546 on: 06/27/2017 03:21 PM »
Hey.  Finally got a copy of Voyage a few weeks ago courtesy of a friend.  It's interesting how things differ between my interpretation on KSP and what happens in the book, especially during the launch sequence.  For instance, I started throttleback for Max Q sooner because I didn't think 40 kPa dynamic pressure was acceptable (I can use MechJeb to give me Q, and the mod Ferram Aerospace Research will give a high dynamic pressure warning if Q exceeds 40 kPa).  I also eject the launch escape tower sooner, and I chose my time based on studies.  I'm actually not sure when the "right" time is to jettison a LES and go to a Mode II+ abort mode.

Offline Ronpur50

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Re: Modelling Mars
« Reply #547 on: 06/29/2017 10:22 PM »
Definitely after SRB jettison!  I would assume shortly after S-II ignition, like was done on Apollo.

Offline Nittany Tiger

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Re: Modelling Mars
« Reply #548 on: 06/30/2017 06:03 AM »
In the book, LES jettison is done shortly after S-II ignition like in a standard Saturn V launch.  I've seen videos of this mission having the LES jettison occur shortly after SRB sep though, while the MS-IC is still firing.  After reading this paper, I went with the latter.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720017278.pdf

From what I gather, the LES was best used while the LV was still in the atmosphere and mostly vertical.  After SRB sep in my launches, the LV is 72 km high and at a pitch of around 35 degrees.  It also has a high vertical velocity, so it's going to be crossing the Karman line pretty quickly.  Therefore, I jettison the LES at 80 km, where the MS-IC is still firing.  I imagine in an abort, the engines would be commanded to shut down and the SPS would fire to push the CSM away from a potentially-catastrophic explosion.

I'm truly not sure of the logic behind when to transition from using an LES for aborts to using a different abort option.  I just went with what I felt was best based on that paper, and it just happens to differ from what's in the book just like how my F-1A throttling timing differs from the book.  I'm not a NASA rocket scientist, so I can't say my way is "correct," but it works well with respect to KSP RSS/RO, which is pretty close to reality.

Offline Ronpur50

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Re: Modelling Mars
« Reply #549 on: 07/02/2017 08:41 PM »
I have always read that the LES was best used in those times as well.  The other part of the LES is the Boost Protective Cover, and it really only had a use in the atmosphere.  So once that was behind, and the SPS could take over, there was no longer a need to carry the extra weight.  I can't wait to see what you are coming up with!!

Offline Nittany Tiger

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Re: Modelling Mars
« Reply #550 on: 07/02/2017 08:56 PM »
Thanks.  I need to get back on the project since it's 90% complete.  I left off on testing the Venus probe, where I used the Huygens probe as a stand-in for the Venus probe.  I didn't know the book actually had a description of the probe, but that's OK for now.  I plan on doing a test run of the mission.

I wonder if they guided the probe for a direct hit with Venus, or just aimed it at the limb of the planet for aerocapture?  The latter seems more likely because of the fewer g-forces on the probe and longer time spent in the atmosphere.  A direct descent is insane, and I've had probes explode from g-overload and overheating trying to aim it straight on (and these probes are rated for 50 Gs in-game I believe, and I can edit the tolerances, but I don't want to create a magical device).

I think I did read about the LES being used as a forward heat shield for ascent, so like you said, it would be logical to just ditch it when the rocket is above the majority of the atmosphere where shock heating is negligible to non-existent because it's just dead weight. 

I know Baxter did his homework for the novel, but he might have taken some artistic liberties, and he might have let some things slide since it's science fiction, and the focus of the book is the story of Natalie and the challenges of a Mars mission in an alternate post-Apollo NASA, not the hardcore technical and scientific details of the mission itself.  I've had a lot of fun researching and simulating the rigorous details of the mission though.  It almost makes me feel like I work at NASA right now given how much I've accomplished for this one mission.  I just want to make something special for it like a video or series.

Was also thinking of pictures and descriptions like what you did with the models, except using KSP screenshots.
« Last Edit: 07/02/2017 10:38 PM by Nittany Tiger »

Offline Ronpur50

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Re: Modelling Mars
« Reply #551 on: 07/03/2017 09:59 PM »
I imagined the Venus Probe to be the same as Pioneer Venus.  Since that never existed in Voyage, it made sense to me that the first probe would be that.  But it is also described as a pie dish, which sounds more Huygens-like.

Offline Nittany Tiger

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Re: Modelling Mars
« Reply #552 on: 07/28/2017 05:54 AM »
There is a description of the probe I think, and they mention it being a sphere with fins within a pie-shaped dish.

"The pressure vessel was a sphere of thick metal.  There were vanes on the sphere to make it spin, so that it was stabilized during its fall, and there were tough little windows cut into the surface so that the probe's instruments could see out."

It's page 470 in my copy.  The pressure vessel is the part of the probe in the pie-shaped heat shield that falls out after the probe gets so far down in Venus that the atmosphere is a superfluid.  In KSP RSS, you can float probes down this way since the terminal velocity is so low that it's lower than many part's crash tolerances.

I'm planning the flight in KSP RSS now.  Might have to move the planets around a bit since planetary motions aren't perfect in RSS.  I've advanced my game to March 17th, 1985, but finding a Earth -> Venus -> Mars trajectory is tricky even with tools for finding flybys.

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