Those gravitational boosts are vital.

The closest in speed so far would be 'New Horizons'. But even then NH is going at 14.5KM/sec compared with Voyagers 18KM/sec. There are no probes currently that would catch up to Voyager.

18km/s is almost understated in terms of speed, so I looked it up to more familiar measures of speed: 65,000kph or 40,000mph. The only thing I really learned here was how even in the thousands of miles or km per hour, it’s just inconceivable how fast that is. Km per second was a better measure after all.

> it’s just inconceivable how fast that is

And even more inconceivable is how slow it still is in terms of human spaceflight outside of the Solar System.

What is crazy to me is that even at those speeds, it is over 18,000 years from reaching one light year distance. The closest star is 4.2 light years away. So to ever reach it we would need multi generational ships or some way to go much much faster.

Round the world in 40 minutes

Travelling from New York to LA quicker than playing the song "From New York To LA"

But the more copies you make of something, the cheaper they become. The R&D cost is the same and is only paid once whether you're building 2 space probes or 2000.

The probe itself is a relatively insignificant cost. The launch costs and timing windows are the limiting factor.

The tyranny of the rocket equation is the fact that to carry more fuel to orbit, you need more fuel to get it into orbit, which itself needs more fuel. That's why gravity assists are so essential for escaping the solar system on a budget.

The planetary alignment that enabled the Voyager launch windows only occurs once every 175 years.

We should definitely be sending out more probes, but we can't just do it whenever we want, at least not without a lot more expense.

The specific alignment for the Voyager missions was to permit flybyes of all the gas giants: Jupiter, Saturn, Uranus, and Neptune, with only two spacecraft. Both V1 & V2 visited Jupiter and Saturn, with Voyager 2 continuing on to both Uranus and Neptune. All visits were flybyes, that is, the probes were within the vicinity of the target planets, but did not orbit them for any prolonged length of time.

More conservative trajectories giving fewer flybyes but relying on more probes would be possible, and are in fact what we've accomplished with the Gallileo & Juno (Jupiter), Cassini-Huygens (Saturn), and New Horizons (Pluto) spacecraft. There are NASA (U.S.) and Chinese proposals for a return visit to Uranus and Neptune, though those remain in planning stages.

<https://www.space.com/nasa-uranus-orbiter-and-probe-mission-...>

The orbiter missions had a much longer time-on-station. For Gallileo, roughly 7 years 9 months, Cassini-Huygens 13 years, and Juno 7 years to date, with another 5 or more possible.

The Ulysses solar probe also flew past Jupiter, using the planet for an orbital assist to both slow it down to approach the Sun more closely and incline its orbit above and below the planetary plane so that the Sun's poles could be observed directly.

> But the more copies you make of something, the cheaper they become. The R&D cost is the same and is only paid once whether you're building 2 space probes or 2000.

The problem with that idea is, except for a few geeks, no one wants to spend that kind of money on space probes.