How quickly could I launch something out of the solar system?
October 2, 2013 6:13 PM   Subscribe

In an aside for a short story I'm writing, a vanity billionaire notices the news about Voyager leaving the solar system, and decides she wants to make her mark on the Universe by 'shotgunning' some things out into interstellar space.

My vague 'spacey-wacey' idea of how this could work would be a satellite get launched into space, then a bunch of small 'pellets' get launched from there towards the sun's gravity well, to be slingshotted outwards. The pellets would only need have enough kit on board to enable people on earth to identify their locations (plus say a message from the vanity billionaire), so as to be able to inform the vanity billionaire when its done.

Can anyone thought-experiment me through a firmer explanation of how it could happen in practice, and particularly a timeframe from idea through to exiting the solar system? How could humanity start littering interstellar space if they started today?
posted by jjderooy to Science & Nature (25 answers total) 1 user marked this as a favorite
 
Do you mean in a terminal velocity kind of way or how many years would it take to do this project kind of way?
posted by tnecniv at 6:27 PM on October 2, 2013


You could probably model it with this

I think the quickest way would be to slingshot around the sun and other bodies, like the Voyager probe did. If you didn't care about tracking it, you could probably send something close to the sun and on a hyperbolic trajectory quite quickly...
posted by baggers at 6:37 PM on October 2, 2013


As an initial way of thinking about this, at a market price of $10k per kg to LEO (Ariane 5), you could throw 50,000 kg up for around $500M (outsourced); since you don't really need insurance maybe a little cheaper. This would be two launches. The remainder of the $1B would be spent on people, project, materials, and the items themselves. If the items need a fuel source that will function outside the solar system, for example if they are to be heralds that spend their future actively broadcasting the glories of Ms. Vanity to the galaxy at large, the cost is immediately prohibitive and it will not work; maybe she buys RTGs from the Russians though.

Assume that you will exit via a tour of the solar system which means some amount of attitude adjustment is going to be necessary and some amount of ground support. Voyager 1 is a good enough model of that, and it was 815 kg (at launch, it's less now). So around 50 Voyagers.

Of course, that's a long trip, and launch windows come into play.

Total cost of V1 + V2 was $968B, btw. Ms. Vanity will do better by outsourcing and buying in bulk (and not having a ground crew or advanced sensors).
posted by rr at 6:41 PM on October 2, 2013


You could do it this way: launch a satellite into low earth orbit equipped with a railgun. Use this to regularly fire small, perhaps bullet-sized capsules close to, but not right at, the sun. With sufficient speed and the right aim, they would slingshot around the sun and out of the solar system. Fire a lot and someone might spot one eventually when it flies near them, especially if they were highly reflective to radar or similar.

Of course, they might assume it was a weapon, especially if it hit someone or ploughed into an inhabited planet. I doubt they would appreciate it, and they might track it back and wipe out our descendants.
posted by baggers at 6:54 PM on October 2, 2013 [1 favorite]


Does immediate speed matter? There's always a flotilla of objects set forth with solar sails. Bonus - the sails could be made so big, that you'd probably see them from Earth for a while too. Talk about vanity!
posted by jquinby at 7:03 PM on October 2, 2013


Response by poster: Thanks for the comments so far. To clarify, I'm looking for the fictional conversation to go something like:

Vanity Billionaire: So how soon from launch could be get something out of the solar system?

Sane Scientist: Well, it took Voyager 36 years to do its 19 billion kilometres ...

Vanity Billionaire: Yes, yes, but I'm not interested in the science - I don't need pictures of planets, or fancy instruments. I want to say hello to the Universe, and I want to say it asap. This is art, with my name on it.

Sane Scientist: Well, if its all about speed, we could launch a minimalist probe and [do x - complicated]

Vanity Billionaire checks phone or something.

Sane Scientist: ... and that would get us out in say [y years].

Vanity Billionaire: That's what I'm talking about!
posted by jjderooy at 7:42 PM on October 2, 2013


It's going to depend a lot on how you choose to define the solar system. If you go with the definition used for Voyager, the edge is where the solar wind stops, called the heliopause.

From my googling, we're not sure what the shape of the heliopause is. It might be a sphere, or it might be a teardrop, or an ellipse.

If you're trying to reach the heliopause and it's not roughly spherical, figuring out which direction to go in is going to be pretty important.
posted by justkevin at 7:58 PM on October 2, 2013 [1 favorite]


ok...voyager is about as big as a small building, mass-wise...using the same rocket (was it a saturn 5?) you could probably catch up to it with your cell phone (plus maybe a small RTG (radioactive battery, like voyager has)) in under 5 years....much less mass to move...
posted by sexyrobot at 8:01 PM on October 2, 2013


how about literally catching up to voyager?...like, cellphone+RTG+like, a freaking magnet...then just piggyback...that would be RAD!
bonus points for it being the phone she had when astronomy became a thing for her...like all pink and blinged out and hello kitty and Carl Sagan's autograph stuffed under the battery cover...
posted by sexyrobot at 8:07 PM on October 2, 2013


Look at the graph of the Voyager Grand Tour here. As you can see, most of Voyager's velocity--in particular, the velocity needed to put it above escape velocity from the sun--came from the probe's gravitational slingshots around Jupiter and then Saturn.

You won't be able to duplicate the rest of Voyager's 'Grand Tour' for another 150 years or so, when all the outer planets have that kind of helpful alignment again, but as you can see from the graph most of the velocity comes from the first two, Jupiter and Saturn, and I believe those are in useful alignments quite a lot more often. Still, you are likely to be waiting X years until you've got a good alignment of those two planets.

As sexyrobot says, you could gain some extra velocity by eliminating most of Voyager probe and equipment and just replacing it with more propellant. Then you would burn this extra propellent in an Oberth Effect maneuver during the period of closest approach to Jupiter and/or Saturn during the gravity slingshot manuever.

This would buy you some additional velocity, though I couldn't say how much exactly without working out a whole lot of details. My sense is, that the vast bulk of the additional velocity comes from the gravity well maneuver itself and the Oberth Effect burn would only add a bit of icing on the cake.

Another option would be to send the probe around the sun first, then to Jupiter and Saturn. You would do your Oberth Effect burn on the way around the sun, which would maximize the effectiveness of the maneuver.

My sense though is that all these maneuvers are going to be only marginally faster than Voyager. They won't be 100X faster, or 10X faster, or even 2-3X faster. More likely, 25% faster or something along those lines.

To get massively higher speeds than Voyager you'd need massively more propellent in solar orbit (to be burnt in one or more Oberth Effect maneuvers) and that's something that even billionaires won't be able to do. The fact that Voyager includes some cameras and stuff doesn't slow it down nearly as much as you would think, because most of its velocity came from Gravity Slingshot maneuvers that are going to work the same regardless of whether you stripped the spacecraft down or not.
posted by flug at 8:21 PM on October 2, 2013


As mentioned above, the best way to get a feel for how this stuff works, and test out some realistic scenarios, is to use the Orbiter Space Flight Simulator.

The paper by G. A. Flandro that outlined the possibility of the Planetary Grand Tour using Gravitational Slingshot maneuvers, as realized by the Voyager missions, is interesting background reading about the whole concept and is available online here.

However, here is the answer I think you're looking for: This paper by Longuski and Williams summarizes the results of an automated system they used to search for 'planetary grand tour' type opportunities.

If you look at Table 1 (p. 364) they summarize a whole bunch of different possibilities, including what year, what planets, and how long it will take.

On that list is the opportunity that comes every 13 years for a mission from Earth to Jupiter to Pluto, arriving at Pluto in only 2500 days. That puts our "megalomaniac space probe" at approx. 40 AU in approx. 6.8 years, whereas Voyager 1 took about 13 years to reach that same distance (that's the distance of Voyager 1's Pale Blue Dot photo, taken in 1990).

So there you go--2X as fast a Voyager to reach that point.

FYI I can't say for certain if Megalomanic Space Probe (MSP) will be going faster or slower than Voyager 1 was at that point. Voyager 1 & 2 both spent a fair bit of time billiarding their way around to various planets in various parts of the Solar System. MSP would save time by going straight to Jupiter then straight to Pluto. But not sure if it's going faster or slower than Voyagers at that point.
posted by flug at 8:52 PM on October 2, 2013


then a bunch of small 'pellets' get launched from there towards the sun's gravity well, to be slingshotted outwards

FYI this won't do anything for you. If you just launch pellets (or whatever) towards the sun they will end up in an elliptical orbit that returns exactly to where they started. So your pellets will end up in a nice elliptical orbit whose furthest point from the sun is 1 AU.

In short, you can't use the sun as a gravity slingshot to escape from the sun's gravity. You have to use one of the planets--and Jupiter, as the largest planet, gives you by far the most boost.
posted by flug at 9:03 PM on October 2, 2013 [1 favorite]


FYI this won't do anything for you. If you just launch pellets (or whatever) towards the sun they will end up in an elliptical orbit that returns exactly to where they started. So your pellets will end up in a nice elliptical orbit whose furthest point from the sun is 1 AU.

Not quite - they'll end up in an elliptical orbit such that when they pass Earth's orbit on the way out they'll be travelling at the railgun's muzzle velocity. (assuming a circular orbit for the Earth, ignoring solar wind, etc, etc, etc)

But yeah, you can't do an unpowered gravity assist around an object to help you escape that object. The Voyager assists worked by shifting some of Jupiter's (and then Saturn's) Sun-relative momentum to the probe. The Oberth effect with a powered burn at perihelion (closest approach to the Sun) could be used to help escape our solar system, but then you're not using dumb pellets any more, and need to build the probe to withstand near-Solar approach.

Since you'd need a powered probe, I suspect that a Mediocre Tour (powered assists at Jupiter and Saturn, but skipping the rest of the outer solar system) would be the best bet.
posted by russm at 10:54 PM on October 2, 2013


How could humanity start littering interstellar space if they started today?

Well, the heliopause is a good start. But anything else is a bit ambitious, barring future physics developments. Voyager 1's not going to be at the Oort cloud for another 300 years, sadly. You may want to read cstross's essay The High Frontier.

small 'pellets'

For those small pellets, I'd suggest microsatellites.
posted by sebastienbailard at 11:02 PM on October 2, 2013


So your pellets will end up in a nice elliptical orbit whose furthest point from the sun is 1 AU.

Perhaps for a while, right?
posted by klausman at 12:06 AM on October 3, 2013


Would you leave the solar system any sooner, and with less effort, if you traveled perpendicular to the orbital plane? (i.e. "straight up") This would mean you'd skip the tour of the planets, but you's also skip dealing with much of their gravitational pull.
posted by Thorzdad at 3:42 AM on October 3, 2013


No, no, the planets are only a teensy percentage of the solar system's gravity well and mathematically all but drop out of the equation. (Jupiter is just 0.0009% of the Sun's mass.) They're incredibly useful, however, for slingshot effects to get you past escape velocity. In fact, Voyager 1 went past Saturn in such a way that it got a gravity boost that sent it out of the ecliptic plane, and if that's where you want to go, you're going to get there a lot more easily that way than doing it with only your own ion drive or whatnot.

For most practical purposes your spacecraft would want to be going someplace specific, thus its direction out of the solar system would be dictated by destination -- and where that bend takes place dictated by available outer planets, or you're getting out and pushing.

Anyway, let's say we are speaking in feasible near-term terms, solar sails are nowhere near practical, ion drives get you nowhere fast, and slingshot effects are never where you want them when you need them. Nukes, then, assembled in orbit and out of regulatory oversight (or by legal loophole, say, on your secret Pacific island base). Or possibly more ideally, a railgun in orbit or on the Moon. But there's going to have to be a bit of engineering and logistical lead time on anything.
posted by dhartung at 4:20 AM on October 3, 2013


Another option to consider: a space elevator to lift a large mass into low-Earth orbit, from which the object can set off to the edge of space. This solves, in part, the difficulty of getting the object off the Earth.
posted by dfriedman at 9:20 AM on October 3, 2013


Nthing everything flug said.

Also, this xkcd what if is on a similar subject, and it might be useful.
posted by Ned G at 2:20 PM on October 3, 2013


My first thought was just slap an ion drive on an RTG, but it looks existing ion drives generally takes about an order of magnitude more power than an RTG provides. Russia has launched a few actual reactors into space on spy satellites which could provide enough power, but those would only generate power for a few years, unlike the decades of power RTGs can provide.

Alternately, you can just do in-space salvage of one of the nuclear weapons platforms that the US or Russia secretly launched during the cold war and use them to power an Orion drive.
posted by ckape at 3:04 PM on October 3, 2013


Just for fun I fired up Orbiter to try out a few scenarios 'in real life' so to speak.

I started in low earth orbit--you're either going to start there or pass through that point on this mission, and from the orbital dynamics standpoint it doesn't make much difference which of those you actually do.

The first thing to understand in anything relating to orbital dynamics, is that in space you're not going to 'shoot something' towards the sun, or whatever, and it will just go there. Rather, you're going to introduce a change in velocity of some sort or other, and that is going to change the orbit of the object, and depending on where that orbit goes, that is where the object will go.

Just for example, if you're in low Earth orbit and you shoot a gun towards the sun, you will NOT end up with a bullet hitting the sun. Rather, you'll end up with a bullet in a slightly different Earth orbit than it was in the first place--and it will not get anywhere near the sun, because the velocity of a bullet is not anywhere near Earth escape velocity, even when added to the (very considerable) orbital velocity of an object in low-earth orbit.

So the situation in low Earth orbit is:

- Orbital velocity (relative to Earth): 7.7km/sec
- Escape velocity (from Earth): 11km/sec

- Orbital velocity (relative to Sun): Ranges from about 24km/sec to 36km/sec depending on which side of the earth you're on (ie, whether your motion is added to the motion of the Earth as it orbits around the sun, or subtracted from it). This is important because it means that you can exit Earth orbit with velocity anywhere from (say) 28km/sec to 40km/sec relative to the sun. Those solar velocities, and their associated orbits are, obviously, very different from each other.
- Escape velocity (from Sun): about 45km/sec

My point has to do with railguns and the like. Wikipedia has a nice article on railguns that gives two basic scenarios:

Railgun #1: A weapon type railgun that fires a small projectile (a few pounds) at 3.5km/sec. This is the type of thing that one could (with only a little stretching of the imagination) imagine being lifted to low-earth orbit.

Railgun #2: A space-launch type railgun that fires a larger projectile (400KG) from Earth surface at 7.5km/sec. This is way, way, way, WAY larger than anything we can envision launching into low-earth orbit at the present time. And the power requirements to shoot even one projectile are HUGE and well beyond what we can handle with current technology. So this is a 'far distant future space fantasy' option.

My point is, that neither Railgun #1 (somewhat realistic under current technology) nor Railgun #2 (futuristic space fantasy) will launch a projectile from low-earth orbit to solar escape velocity.

Railgun #1 is actually rather pathetic, and starting at LEO and firing at the point of maximum velocity relative to the sun, even the very small and light railgun projectile will barely reach even Earth escape velocity. It launches at 7.7km/sec (orbital velocity relative to Earth) and adds 3.5km/sec to that for a total of 11.2km/sec relative to Earth--just above escape velocity.

Relative to the Sun, we wait until the point in our orbit around the Earth where we can launch the small Railgun #1 projectile at max delta speed to the sun (36km/sec). The railgun adds another 3.5km/sec for a grand total of 39.5 km/sec orbital velocity relative to the sun--well below escape velocity.

So the Earth ends up with another very small moon, but we're not even close to leaving the solar system here.

Railgun #2 does a little better.

We end up at 15.2km/sec relative to Earth, so well above escape velocity there.

But from the sun perspective, we have 36km/sec + 7.5km/sec for a total of 43.5km/sec. So we're well under escape velocity there.

We end up with another object orbiting the sun in the general vicinity of the Earth, and nothing more than than that. Not even close to leaving the Solar System.

I tried another similar scenario--let's call it "Super Duper Railgun #3" which is capable of shooting its projectile at 9km/sec. FYI to achieve this delta-v using a rocket in Orbiter, I needed about a 1000 second burn, which is HUGE (an entire Saturn V burn, all three stages added together, is only about 1200 seconds).

This was just enough reach solar escape velocity. From that start I let it fly at maximum time compression for as long as I had patience. When I gave up on it, it had traveled 144 AU from the sun in about 40 years, current speed about 16km/sec.

By way of comparison, Voyager 1 is now 125 AU from the sun and traveling 17km/sec after 36 years.

In short, railguns of any even semi-realistic sort are going to do worse than Voyager, not even escaping solar orbit. Even our super-energy-hogging "direct escape" from the low-earth orbit doesn't do any better than Voyager 1.

Unless you really want to get into just straight space and science fantasy, your quickest way of exiting the solar system is going to be some optimization or enhancement to the gravity slingshot ideas used by missions like Voyager and the speed improvement is likely to be incremental rather than astonishing. You can imagine things like optimizing the gravity slingshot maneuvers for max exit velocity rather than max planets visited, and converting maybe 3/4 or even 9/10s of Voyager's 1800 pounds of spacecraft mass in more propellent, which will result in somewhat higher final spacecraft velocity.
posted by flug at 5:07 PM on October 3, 2013


in-space salvage of one of the nuclear weapons platforms that the US or Russia secretly launched during the cold war and use them to power an Orion drive

Yes, the old atomic bomb drive is certainly capable of getting places much faster than anything we've discussed here (somewhere between 20 and 200 times faster). But even just one atomic bomb is more in nation-state territory than 'one wacky rich person' territory, and for Orion you need materials for the equivalent of many, many atomic bombs plus the rocket & space technology on top of that, plus the technology to put the two together.

An idea more in 'one wacky rich person' territory is this--using a single, small-ish atomic bomb explosion to launch a projectile from Earth's surface at well over both earth & solar escape velocity.

Of course, that has a 0% chance of working in reality, because the Earth's atmosphere will slow the projectile to well below escape velocity long before it hits outer space (see the linked article for the explanation). But as a literary device, this has some promise because your premise could be that your sane scientist has found a real solution to that issue, maybe by increasing the initial speed to say 20X escape velocity and doing something or other to dramatically reduce the atmospheric friction of the escaping plug. So it loses some velocity in the atmosphere but still exits with say 10X escape velocity.

Or maybe the "plugship" is launched from the moon, solving the atmospheric problem instantly. Honestly its far more feasible to envision transporting one small-ish nuke to the moon, plus some drilling equipment or whatever, than (for example) taking rail guns and all the complex power-generating and construction equipment that goes with them to the moon, as some suggested above. Plus, the atomic bomb plugship ends up reaching many times the velocity of even a large, complex rail gun.

At that point you've got a simple projectile exiting low-earth orbit at somewhere around 110km/sec, putting it 3-4 times faster than Voyager. Or it's exiting lunar orbit at ~220km/sec, giving us 6-8 times the velocity of Voyager.* And we readers could probably swallow a scenario where a wacky rich person could come up with a single small-ish nuke from somewhere . . . transporting it to the moon and doing a whole lot of horsing around with it there--I'll leave it to you to decide if that is really believable. Maybe he sells it to the Chinese as the primary goal of their upcoming moon missions or something . . .

I'm assuming you can figure out the reasonable enough time estimates for your purposes, based on these figures. Voyager 1 took 36 years to travel 125 AU from the sun. So 3-4 faster would be 8-12 years to reach 125 AU and 6-8 times faster would be 4-6 years to reach 125 AU. These are approximations, of course.
posted by flug at 6:06 PM on October 3, 2013


This will be easier if you convince your billionaire that getting somewhere is more important than leaving the solar system — Voyager is not going anywhere in particular, so if you aim your probes right, you'll greatly improve the odds of getting found by aliens before Voyager.
posted by Tom-B at 7:39 PM on October 3, 2013


Unless you really want to get into just straight space and science fantasy, your quickest way of exiting the solar system is going to be some optimization or enhancement to the gravity slingshot ideas used by missions like Voyager and the speed improvement is likely to be incremental rather than astonishing.

Optimising your gravity assists for pure speed rather than science value would be pretty easy. Voyager 1 passed Jupiter at almost 4 times the planetary radius, and Saturn at a touch over twice the planetary radius. Dropping those approaches as close as possible to the atmosphere and doing a powered assist as deep in the planetary gravity well as you can would give you a significant boost over what the Voyagers achieved.
posted by russm at 9:39 PM on October 3, 2013 [1 favorite]


FYI this article is an excellent discussion of the gravity assist maneuvers, how they work, how they worked for the Voyager missions, and how the effect can be maximized for various purposes. The graphical explanations are very good as well.
posted by flug at 11:47 PM on October 4, 2013


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