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I ask because I have a problem trying to find an appropriate launch window around that time or any point in the mid-1980s, and I need to reach Jupiter via Hohmann transfer so I can then use a series of Oberth manoeuvres to get to Pluto from there, with my nuclear spacecraft having a delta v of 100 km/s. Problem? The launch window and time it will take before the spacecraft can reach Jupiter, and get to Pluto from there.

So, how long would it take to reach Jupiter and get to Pluto from there and the other gas giants via Oberth Manouevre, and what would be an appropriate launch window?

And this is a combat operation so..........yes.

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  • U are sure it's military operation, u are ok to wait 9 years to fly having 100km/s delta budget? Take look at voyager 1,2 orbits. What you wish is not for 100km/s delta craft. pluto period is 248 years - so only factor which repeat himself is Jupiter with 11.9y orbital period. As here read begin, find that magazine record. Head directly, will be devastating surprise for your enemies, strike them in 4 years time. – MolbOrg Jul 13 '16 at 0:48
  • @MolbOrg Are you sure it would take a four year trip to Pluto directly and with a Hohmann transfer? – Future Historian Jul 13 '16 at 0:55
  • No, not sure, it's rough estimation. I'm sure it's not hohmann orbit. Escape velocity on earth orbit is 42kms, best case scenario you add 11 km/s to earth velocity and 40 on top, left 40 to slow down later, 9 for maneuvers. So average speed will be around 60km/s. 12 a.u. per year. Start windows each year. With oberth maneuvers near sun probably 2 windows per year or more wide single windows, will cost some delta trough. – MolbOrg Jul 13 '16 at 2:30
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The Wikipedia article on Hohman orbit transfers is useful. My superficial reading of it suggests the velocity you require is only 8.8 km/sec. Far below your delta V of 100 km/sec.

What may help you is the fact that Hohman transfer orbit is the perihelion of the departure planet and this connects to the aphelion of the destination planet. Therefore, search the times when Earth is perihelion during the 1980's and Jupiter is in aphelion. Do a quick estimate of the time taken at 8.8 km/s and find which Earth perihelion is most likely to connect with a Jupiter aphelion. This will give you your launch window to Jupiter.

Right now I'm afraid the question about going on to Pluto will take more research. This may be a useful first step.

However, the Interplanetary Transport Network concept may be worth looking at. It uses gravity assists from one planet to travel to further destinations and uses less energy. The references at the bottom of the article has downloadable PDF's on the subject. The American Scientist PDF mentions the profile of a trip to Jupiter.

The inevitable YouTube has this enter link description here about the IPN and there are other videos in the links menu. Apologies if this is turning into link rot, but time is short and research is long. I hope I've given you something to start finding an answer.

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  • No need for concern. I just have to consider this is an Orion military spacecraft and I have no idea how many 5 kilotonne warheads I need. :/ – Future Historian Jul 14 '16 at 14:34
  • I did a search and found the Wikipedia entry on the Orion Project has figures for pulse unit sizes and numbers: en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion). It links to en.wikipedia.org/wiki/Nuclear_pulse_propulsion As a bonus the NASA monologue on NPP can be downloaded as a PDF at ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20000096503.pdf There should be space for 5 kt warheads. – a4android Jul 15 '16 at 11:12
  • Dumb, dumb. That's 'NASA monograph" not "NASA monologue". I should go and have my head read. – a4android Jul 17 '16 at 4:27
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Your question fails to take the power of a nuclear pulse drive into account. The ORION nuclear pulse drive is the only high thrust/high ISP drive known to modern science, and theoretical calculations done back in the late 1950's and early 1960's, while the drive was under active investigation, suggested that 4000 ton spacecraft could be assembled on the ground and launched directly into space and on trajectories to Mars, and later the investigators hoped build ships to get to Saturn.

ORION around Mars 1975

Mars 1975

And this is with 1950 era technology....

Using Hohman transfer orbits is the means to get from place to place in the solar system using the minimum amount of energy, which makes sense when you are using a chemical rocket with far lower ISP, or a low thrust, high ISP drive like an ion thruster or light sail (this isn't strictly true, since after a while you will have built up an enormous velocity, but in practice you will be using thrust for weeks and months to build up that kind of velocity).

Ion drive ship Are we there yet?

While ORION isn't exactly a torch drive (where you simply point at the planet you want to go to and blast away, flipping at the halfway point to decelerate), it does have more than enough performance to allow you to ignore Hohman transfer orbits. Perhaps the only reason you might need to do this in an ORION drive ship is you have depleted your reserve of nuclear pulse units, and need to drift on a minimum energy orbit back to base. Realistically, it would be easier for the base to send another ORION ship to you with fresh supplies.

This is the obligatory link to the Atomic Rockets page, which will help you conceptualize ORION and what exactly you can do with it. As a somewhat ridiculous aside, there is an even higher performance version of the ORION concept, called MEDUSA While this ship needs to be assembled in space, it theoretically will leave first generation ORION's in it's radioactive dust....

A visualization of the concept is here:

enter image description here

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  • Spot on details about ORION nuclear pulse vessels. Launching from Earth has global radiation hazard issues, but you that I'm sure. Nuclear disarmament killed Project Orion. Freeman Dyson had no regrets understandably. MEDUSA is wonderfully insane. The OP only a delta V budget of 100 km/s. Somewhat smaller capacity than NP ships could have velocity wise. A combination of NP propulsion & ITN should be interesting. Energetically economical too. – a4android Jul 14 '16 at 6:58
  • To be honest. I did consider that but you have to remember: how many 5 to 15 kilotonne warheads will I need to even get to Pluto with ignoring a Hohmann Transfer? And did someone forget how to return to Earth AND combat manoeuvres? – Future Historian Jul 14 '16 at 14:33
  • You need to define your requirements in advance. Atomic Rockets has some tables to help you: projectrho.com/public_html/rocket/engines.php – Thucydides Jul 14 '16 at 20:09
  • You need to define your requirements in advance. Atomic Rockets has some tables to help you: projectrho.com/public_html/rocket/engines.php; projectrho.com/public_html/rocket/…; projectrho.com/public_html/rocket/… – Thucydides Jul 14 '16 at 20:15

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