Undocumented alien caught stealing orbits in our Solar System Scientists have discovered the first “interstellar immigrant” living among our Solar System's matter. Unlike Oumuamua, the asteroid that made headlines for appearing to be a gigantic spliff or a potential alien spacecraft, asteroid (514107) 2015 BZ509, affectionately known as Bee-Zed, has been circling the Sun for some 4.5 …
An object in retrograde orbit has so much relative velocity relative to Earth that it might just be one of the most difficult possible destinations in solar orbit to reach. Earth orbits at 30km/sec. Roughly speaking, all that velocity has to be neutralized. Then the probe has to catch up with the retrograde target, however fast that happens to be moving. This is either going to take a huge, massive rocket, probably huger than anything humanity has put into space before. Or a centuries-long journey through, possibly, Jupiter's Lagrange points on a low-energy complex trajectory.
The alternative to all that is a close encounter at a minimum of 13km/sec (~Jupiter distance velocity, probe at aphelion of prograde orbit), with a tiny, cold object that you're passing on a prograde trajectory while it's going the other way. Not much of a mission if all you have time for is a single blurry picture.
...or a solar sail...
That will take you downwind only, like a balloon in a steady wind. Nice but totally rudderless, and you will start out with the speed of the earth around the sun of about 108,000 km/h. There is really no sailing, as we who know, know it, in a solar sail, no rudder no lateral plane. You would leave the sun like a corkscrew, round and round, further and further.
Once you're in space, Orion isn't an issue. It's just the pesky part about getting past the atmosphere and all that biological stuff which poses a problem.
Freeman Dyson calculated that the cumulative cost of an Orion launch was 1-2 extra deaths per year due to fission products in the atmosphere and concluded this was too high a price to pay for a launch. Compare and contrast with most companies which would happily let hundreds of people die as long as their product is sold and marketshare increased.
FWIW one of the things which killed Orion was presenting the concept to JFK as a launching a multithousand ton "space forttress" into orbit capable of lobbing nooclear weapons at any location on the planet and dodging whatever was fired at it thanks to the manouevring capabilities inherent in the propulsion system. He was horrified by the concept and reportedly ordered it shut down the following day.
Would it be possible to get to a retrograde orbit with a very close pass of Jupiter? Possibly multiple passes, possibly including Saturn passes as well?
I suspect anything's possible.
The main question is how long a mission you want (a lazy, looping trajectory over the course of decades, with the associated ground monitoring and support), or whether you have access to a significant propulsion system that can scrub quite a lot of your dV for you and accelerate the process. As another poster mentioned, we're talking about slowing down by >10 km/s and then putting it back on in the opposite direction.
At that range of course solar isn't much use, so for your power source you're looking at an RTG which means your maximum mission life is determined by the rate at which your isotope cools and electricity generation drops off (based on Voyager, gives you at least 40 years, but probably not more than 60).
What other posters are hinting at is ultimately the "Interplanetary Transport Network", which is a grandiose way to describe replacing propellant expenditure with computational power. The theory behind the ITN is that due to the transient stability of a Lagrange point halo orbit, a very small dV can define a wide range of exit trajectories. If any of those trajectories intersect a Lagrange point somewhere else, then the spacecraft can jump between points at extremely low cost. This is one of the possible mechanisms for explaining how natural objects (which have, in a human sense, no controllable thrust) wind up in retrograde or other weird orbits to begin with.
The downside: To get between planets might take centuries. Part of this is because possible trajectories don't always intersect a useful destination until planets/moons align in the right place. The other reason is that drifting between points is extremely slow compared to high energy 'conic' travel.
I suspect any probe sent to this asteroid would end up doing multiple gravity assists, exactly what bodies it would encounter would depend on when it was launched.
If you were just going to use brute force, a more efficient way might be* to start out by boosting from an Earth orbit up to a very eccentric (ie oval shaped) orbit with a really high aphelion (ie the furthest point in the orbit would be out by Pluto or something). Then once you're all the way out there the orbital velocities are a lot smaller so flipping your rotation would only require prodigious use of deltaV, not utterly ridiculous amounts.
Then you just need to match velocities once you get back down level with it, avoiding any unwanted interactions with the other planets on the way.
* I've not done the maths, it might not work.
@Mark 85.
Since any entry documentation is lost or long gone it is illegal and clearly in a 'Hostile environment'
So it should only be a matter of time before the relevant authorities catch up with it.
As a non-rocket scientist with the maths abilities of a lump of cheddar; would it be possible to send a probe the wrong way around the sun to achieve a braking effect rather than a slingshot effect and then use other sources of gravitation to accelerate it in a retrograde orbit to catch up with the immigrant?
What we see (and hear) is the gas layer, sure. The outstanding question is how large is the rocky ego at the core. Might be huuge. At least the density is the best ever. Perhaps there will be some gravity detected at some point which can be used to compute the mass... Perhaps. Perhaps not. I don't know.
We in the mighty and free United Kingdom will have nothing to worry about from alien asteroids. After next March we will have control of our borders, policed by the powerful RAF Air (and Space) command. Any cheeky asteroids trying to smash into the Home Counties will be turned back by our wonderful Border Force personnel and told to go back where they came from.
Of course they could sneak across the non-border into Norn Ireland and then take a ferry to Liverpool...
Best comment I saw was on Twitter and along those lines. It said something along the lines of "Don't tell the Home Office - they'll arrange to have a thruster landed on it, and use that to send it back where it came from."
(Can't be arsed to find/link to the original tweet.)
Nice one. But no problem telling the Home Office. Their inability to successfully organise anything more complicated than a morning cuppa and a Digestive is well known. We'd end up with dozens of hungry asteroids in parking orbits, waiting for their thrusters.
The Home Office Christmas Party must be an absolute disaster!
BeeZee and other objects could have come from the another galactic arm. Boffins some years ago stated that the matter in our galaxies arms separate away based upon mass as the more massive stuff leaves the lighter stuff behind, we in the following arm catch up to this lighter matter and it becomes part of out galactic arm for a while.
Just what would would be left behind is speculation while the other moves onward would probably be just dust & hydrogen but it could include a stray object or two with eccentric orbits.
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The simulations indicate that (surprise!) this object's retrograde Jovian orbit is stable. Okay. Don't understand it, but I can believe it. What I cannot believe is that this single fact is enough to infer that the object has been here for five billion years. Why not one million? Or 100,000? Moreover, I understand that the gas giants formed closer in and then migrates out. Is this still believed? If so, does the simulation indicate a stable orbit during such a transition?
Problem #2: How does item #1 imply that the object is extra-solar in origin? Could we not have an Oort cloud object get knocked by Neptune to Saturn to Jupiter with at least as great a probability?
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