WI: Soviets Launch Yupiter Program

They'd have to have done a flyby first as a sort of "rangefinding," much like Pioneer 10/11, and this is a period where the Soviet program was very cash-strapped--note that after 1973, they basically abandoned their Mars program even though it's quite possible that it was about to turn a corner into success (they were using similar busses to the Venera series, and that program had finally sorted out its own bugs, so Mars might then have followed). If they were shuttering Mars, I really think a whole new bus for "Yupiter" flybys and then an orbiter in the mid-to-late 70s is...unlikely.
I really think they would've just used a light-weight version of the Venera/Mars bus to get a Jupiter flyby.
 
I really think they would've just used a light-weight version of the Venera/Mars bus to get a Jupiter flyby.
There were several variants on the Venera/Mars bus, growing increasingly heavy after they switched from Molniya rockets for launch to Proton. From what I can see, the Proton orbiter busses were all at least 2 tons, not counting fuel or landers. That means they're all way, waaay too heavy to be cut down to under a ton-and-a-half (not to mention the need to convert to RTG--not an easy change). You'd almost need to start from the 1960s-era Mars 1/Venera 1-6 bus, but then update it...it's really going to be a brand new bus.
 
There were several variants on the Venera/Mars bus, growing increasingly heavy after they switched from Molniya rockets for launch to Proton. From what I can see, the Proton orbiter busses were all at least 2 tons, not counting fuel or landers. That means they're all way, waaay too heavy to be cut down to under a ton-and-a-half (not to mention the need to convert to RTG--not an easy change). You'd almost need to start from the 1960s-era Mars 1/Venera 1-6 bus, but then update it...it's really going to be a brand new bus.
Hmm... I see, but the way you said it sounded like you meant making a brand new completely different bus, which was unrelated to Venera/Mars. Also, which "Mars-1" do you mean, do you mean the one without the lander (It was similar to Mars 2 and 3, but with no lander) or "Mars-1M", or Marsnik, as was named by western media.
 
Hmm... I see, but the way you said it sounded like you meant making a brand new completely different bus, which was unrelated to Venera/Mars. Also, which "Mars-1" do you mean, do you mean the one without the lander (It was similar to Mars 2 and 3, but with no lander) or "Mars-1M", or Marsnik, as was named by western media.
I meant Mars 1, the one that was a modified Venera bus. Still, once you account for conversion of the entire power system, updating avionics, and improved communications...it's really not that easy a change, and I don't see them doing it at the same time they were cutting Mars, where the technology jump between consecutive spacecraft was a lot smaller.
 
A really quick look at delta-vs on the internet suggests that a Jupiter mission needs about twice the delta-v as a Venus one. That MAY be orbiters.

Still. Especially given Soviet low energy hypergolics (vs LH/LO the US used for such upper stages), your mass fraction to Jupiter would be pretty low. No?
 
Yeah... so you're essentially saying that it was impossible for the Soviets to launch a Yupiter-1.

EDIT: Also, there was a reason I made this thread other then curiosity, basically I have this alternate history idea were Khrushchev ends up being much more anti-Stalinist, and is essentially a democratic socialist, and when/if I write about it, I think I'd first focus on the space exploration part, and the Yupiter program is in it. (And yes, I was partly inspired by your awesome Eyes Turned Skyward, e of pi ;))
 
Also, sorry to get a bit off-topic, but here are the list of Yupiter missions in that AH of mine:

Yupiter-1: Launched in 1968, it has a modified version of the Venera/Mars orbiter bus with RTGs, and it's LV is a Proton-K. Supposed to do a Jupiter flyby, but it's 2nd stage cuts off 29 seconds after ignition, leaving it on a suborbital trajectory where it burns up in the atmosphere.

Yupiter-2: Launched in January 1971, almost identical to Yupiter-1, but this time, it's successful. It arrives at Jupiter in October of 1972.

Yupiter-3: Launched as a twin to Yupiter-2, but communications with it are lost 1 month before it's Jupiter encounter.

Yupiter-4: Launched in April of 1973, it was similar to the previous Yupiter spacecraft, but it would follow the same course as Pioneer 11, were it would flyby both Jupiter and Saturn, and it was successful.

Yupiter-5: Twin of Yupiter-4, but it was stranded in Earth orbit as the engine failed to ignite to do the trans-Jovian-injection.

Yupiter-6: Launched in 1975, it was intended to be a Jupiter orbiter, like the IRL Galileo, it was launched on an N1 (The final N1 to be launched), but an engine fire in the 3rd stage right after ignition caused it to literally explode, and thus it became the final Yupiter probe, and the Yupiter program came to an because of it, as flybys had already been done and an orbiter required an N1, which there were no more of.
 
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