How would I or who/what could help me figure out the trajectory taken by an "Extended Grand Tour" space probe launching around 1972, preferably without me having to take a long series of courses on the subject?

[Grant Exploit]

(This was first posted on the Space Exploration StackExchange and the AskScienceDiscussion subreddit first, but I want more input, so I'm posting here as well.  As forewarning, the most integral details of this question are bolded.)

For context, I have been writing an alternate history involving the accelerated development of spaceflight technology for over 5 years now (one with quite different assumptions from other examples of the subgenre), and one of its long-standing elements has been a wildly-ambitious space probe that would be sent on a Solar System Circumnavigation through a Grander Tour.

What does this mean? Well, here are the mission objectives:

1. The main spacecraft body (which I will obfuscatorily name “the Spacecraft”) must fly by every planet (1930–2006) in the Solar System save Pluto.

2. At least a subprobe (“Subprobe A”) must fly by Pluto.

   • Double points if it manages to do so while flying by all 8 other planets.

3. A sample, no matter how miniscule (probably micrometeorites or ring particles), must be returned to Earth by a subprobe or sub-subprobe (“Subprobe B”) after flying by all 8 2006– planets.

   • The course correction to do so may involve as much as an orbital-scale (~9000 m/s) multi-stage solid rocket together with aerobreaking and/or a brutal gravity assist.

   • Double points if it is on or launched from Subprobe A.

   • Triple points if it is on or launched from Subprobe A after the Pluto flyby.

4. Each flyby in the Outer Solar System should preferably be at least 1 synodic period before that of the real-life Grand Tour users the Voyagers in order to prepare for the arrival of a vaguely equivalent program.

The base of the spacecraft’s conception was that it would be launched around the time of or before the first outer planets and interstellar probes in real life (Pioneer 10/11) to make time for it to engage on a more proper Grand Tour trajectory. This was reinforced by the fact that said time range roughly overlaps with the 450^th anniversary of an Earth circumnavigation expedition done by the crew of a certain navigator, who happens to be the namesake of a far less impressive real-life space mission.

So, the rock-hard minimum and maximum are the 450^th anniversary of the start of that navigator’s voyage (September 20^th, 1969) and the launch of the latter Pioneer, Pioneer 11 (April 5^th, 1973). However, it would ideally be launched before September 6^th, 1972, exactly 450 years after what was left of that expedition returned, yet as close to that date as possible (i.e. within 1972) to allow as much advanced technology to be used in it as possible—the spacecraft would include developments like 8-bit microprocessors, helical-scan tape data storage, robotic arms, synthetic aperture RADAR, and possibly non-solid-state radioisotope generators. And yes, the first asking of this question was deliberately timed to match with the 50th anniversary of that date and the 45th anniversary of the launch of Voyager 1. (I’d have preferred it to be earlier, but ehh…)

Also, the spacecraft’s original conception had it launched on a Saturn IB–Agena D (what I thought was the highest-capacity high-velocity non-Saturn V notional “drop-in” vehicle that could have been made at the time… ignoring that either a Saturn IB–Centaur or earlier Titan IIIE would have greater capacity and could probably be made with similar R&D), but as its size and capabilities grew, its proposed launch vehicle was progressively upgraded until it became the “Saturn 1E-SB”, which consists of 4 stages (more details on which could be provided if required), the last one, not considered integral to the launch vehicle’s identity, being the main course correction stage of the spacecraft.

The first 3 stages would have the capability to put the 4th stage and ~5.5-ton spacecraft complex—~28.5 tons in total and ~6.75 tons dry mass—on a trans-Cytherean or potentially trans-Martian injection (up to 3650 m/s tested in KSP RSS RO using a penultimate version of the launch vehicle, probably ~3800 m/s), beginning its Grander Tour… A Saturn V could do so, too, and to be honest I now find justifying the existence of the Saturn 1E-SB somewhat difficult, so I may bite the bullet of switching away from a “Saturn one” platform.

Now, how much ∆v would the course correction stage be capable of supplying? A measly… ~5500 m/s. And that’s with the subprobes still attached. So there is a very beefy, though not unlimited course-correction capacity.

Now, orbital mechanics is a complex business, and I don’t know if it would even be possible to fulfill even the barest mission requirements given the ∆v budget within that launch window, let alone how it would be done. However, the existence of trajectory designs like this, a flyby of all 2006– planets launched in the same vague timeframe with a negligible course-correction budget, indicates its likely possibility. Note that the 5500 m/s and 5.5 tons payload is a maximum and minimum, respectively—the more optimized the trajectory can be made, the smaller the fuel mass of the course correction stage needs to be, allowing a greater scientific payload, so the more optimized the mission is, the better.

And so, the question. Ideally, I’d like to have the specifics of this drilled down by April 5^th, 2023 for some sense of timeliness. For more context, this is the encounter order as planned when the conception of this mission reached its modern form:

Main spacecraft: Earth→Venus→Mercury→Venus→Mars→Jupiter→Saturn→Ouranos→Neptune→Interstellar

Subprobe A: 〃→〃→〃→〃→〃→〃→Pluto→Interstellar

Subprobe B: 〃→〃→〃→〃→〃→〃→〃→Ouranos→Neptune→Earth

[magnemoe]

Thanks for the link to the video, very impressive. Only issue I see is an 140 km Earth flyby would be very close. 

[wumpus]

Thoughts on 1972 tech:

Wasn't that roughly the time the nuclear thermal rocket was grandfathered into the current readiness state?  That makes it a lot easier.  You really don't want to do this without a NTR.

Communications to and from 1972 tech would be iffy.  Pretty sure the only reason they can still communicate with one of the Voyager probes is thanks to some extreme (old school) hacking that updated the radio coding.  Trying to get put control and communications for the return sample will require a fairly hefty return vehicle.

"Return sample".  Picking a particle out of a ring of a gas giant is one thing, but if you require a ground sample from Venus you are asking for something well beyond 1972 tech, and likely 2022 tech.  Look what has gone into just getting a sample back from Mars, and remember that you have to sample and return almost immediately to your entire rocket melting.  You also have scaling working against you (see the fun in landing on Eve in KSP), so will need a significantly bigger rocket than the smaller (pre-1972) rockets used to escape Earth's atmosphere.  I'd also assume that such a rocket would have to be hypergolic (how are you going to keep cryogenic fuel liquid during the descent and ascent on Venus)?  Which means a huge amount of hypergolics launched from Earth (try to sneak in before the clean water act...).

Calculating the trajectories: pretty sure you are limited to patched conics, just like KSP.  The fancier orbital tricks (interplanetary highway) wouldn't be discovered until later, and your most powerful computer available is the CDC7600 (Cray 1 was 1975).  34MHz, less than 4M (Meg, not Gig) of RAM,  10MFlops.

[Gargamel]

https://trajbrowser.arc.nasa.gov/traj_browser.php

A quick google search turned up that and a whole bunch more.  That tool might not do exactly what you want, but I know there has to be a tool online somewhere to do this. 

[SunlitZelkova]

15 hours ago, wumpus said:

Wasn't that roughly the time the nuclear thermal rocket was grandfathered into the current readiness state?  That makes it a lot easier.  You really don't want to do this without a NTR.

NERVA was not expected to be ready until the late 70s. In 1973 the experimental ground stuff was just finishing up.

15 hours ago, wumpus said:

Communications to and from 1972 tech would be iffy.  Pretty sure the only reason they can still communicate with one of the Voyager probes is thanks to some extreme (old school) hacking that updated the radio coding.  Trying to get put control and communications for the return sample will require a fairly hefty return vehicle.

Pioneer 10 was launched in 1972 and remained in communication until 2003.

15 hours ago, wumpus said:

"Return sample".  Picking a particle out of a ring of a gas giant is one thing, but if you require a ground sample from Venus you are asking for something well beyond 1972 tech, and likely 2022 tech.  Look what has gone into just getting a sample back from Mars, and remember that you have to sample and return almost immediately to your entire rocket melting.  You also have scaling working against you (see the fun in landing on Eve in KSP), so will need a significantly bigger rocket than the smaller (pre-1972) rockets used to escape Earth's atmosphere.  I'd also assume that such a rocket would have to be hypergolic (how are you going to keep cryogenic fuel liquid during the descent and ascent on Venus)?  Which means a huge amount of hypergolics launched from Earth (try to sneak in before the clean water act...).

Lavochkin (I think) has made a proposal for a Venus sample return that would not require going to such lengths.

This is not that far fetched for 1972 if someone really wanted to do it. The Soviets launched balloons to Venus with more or less identical technological levels in 1985, and hypothesized about floating cities in 1971.

[magnemoe]

2 hours ago, SunlitZelkova said:

NERVA was not expected to be ready until the late 70s. In 1973 the experimental ground stuff was just finishing up.

Pioneer 10 was launched in 1972 and remained in communication until 2003.

Lavochkin (I think) has made a proposal for a Venus sample return that would not require going to such lengths.

This is not that far fetched for 1972 if someone really wanted to do it. The Soviets launched balloons to Venus with more or less identical technological levels in 1985, and hypothesized about floating cities in 1971.

Now the return rocket will be as large as something able to put an CubeSat into orbit, sample might be smaller but you need to put this into an pretty presise orbit so it can be picked up in Venus orbit. 
Then you need the shell, the balloon and the sample equipment. Say 2-3 ton for the return rocket as an minimum, say 5-6 ton to the surface then you need the probe returning to earth. 
More realistic I say the setup might be closer to 10 ton something. 

[wumpus]

8 hours ago, SunlitZelkova said:

This is not that far fetched for 1972 if someone really wanted to do it. The Soviets launched balloons to Venus with more or less identical technological levels in 1985, and hypothesized about floating cities in 1971.

I think the real question is how do you decelerate an orbital craft (more likely yet another staged specific vehicle) down to the venusian wind speed, capture the payload from the balloon, and then accelerate back to orbital velocity and dock with the main craft?  This at least breaks down the number of stages significantly (and reduces the amount that has to be shielded from the full wrath of Venus's heat) but really doesn't reduce the total delta-v needed.

The sample return is a huge addition to the problem.  It adds huge amounts of delta-v and requires all kinds of thrust as well.  Also fun if you  have to deal with the heat of a Mercury approach with virtually the entire ship.

As an aside, if you want the entire vessel to see at least 8 planets, you want to launch well before 1972 to get to Venus/Mercury/Mars first.

5 hours ago, magnemoe said:

Now the return rocket will be as large as something able to put an CubeSat into orbit, sample might be smaller but you need to put this into an pretty presise orbit so it can be picked up in Venus orbit. 
Then you need the shell, the balloon and the sample equipment. Say 2-3 ton for the return rocket as an minimum, say 5-6 ton to the surface then you need the probe returning to earth. 
More realistic I say the setup might be closer to 10 ton something. 

I think the size of Apollo-era guidance computer was a good sized cubesat on its own, and the mechanism to grab a return sample won't be that small (note that "obtaining samples" has been notoriously hard in practice).

[magnemoe]

9 minutes ago, wumpus said:

I think the size of Apollo-era guidance computer was a good sized cubesat on its own, and the mechanism to grab a return sample won't be that small (note that "obtaining samples" has been notoriously hard in practice).

You have a good point so the upper stage has to be significantly larger so N1 or Saturn 5 will not cut it. 

Anyway if you want to do sample return and not the moon, do an asteroid or Mars. Mars has a bit of the same problem, because of miniaturization the planned Mars sample return mission uses something the size of an guided anti tank missile to get the samples into an orbit so the return craft can collect it. In the 70's you probably need something more like the red dragon return rocket to get into orbit, so lander will be heavier than anything we landed on Mars. 

[SunlitZelkova]

14 hours ago, wumpus said:

I think the real question is how do you decelerate an orbital craft (more likely yet another staged specific vehicle) down to the venusian wind speed, capture the payload from the balloon, and then accelerate back to orbital velocity and dock with the main craft?  This at least breaks down the number of stages significantly (and reduces the amount that has to be shielded from the full wrath of Venus's heat) but really doesn't reduce the total delta-v needed.

The Lavochkin proposal does not involve any atmospheric rendezvous, the ascender is inside the lander, floated up to an altitude where the rocket doesn’t have to contend with the monster Venusian surface pressure, and then blasts back into orbit.

14 hours ago, wumpus said:

The sample return is a huge addition to the problem.  It adds huge amounts of delta-v and requires all kinds of thrust as well.  Also fun if you  have to deal with the heat of a Mercury approach with virtually the entire ship.

As an aside, if you want the entire vessel to see at least 8 planets, you want to launch well before 1972 to get to Venus/Mercury/Mars first.

It would definitely make more sense to split these into different missions and launch an armada than doing a single massive craft.

The real life Grand Tour was to the outer planets only, because it could actually be done relatively easily and made sense. It was quite efficient for trying to get as much science done as possible.

This one takes the concept too far and is trying to do inefficient things.

14 hours ago, magnemoe said:

In the 70's you probably need something more like the red dragon return rocket to get into orbit, so lander will be heavier than anything we landed on Mars.

The Soviet 5M Mars sample return proposal, which would have launched on an N1, used a big lander and a direct ascent profile (no rendezvous), which contrasts with the tiny NASA-ESA approach.

By the looks of it China is going more along the lines of a direct ascent profile similar to the Soviets, IIRC.