Why has the US been the only country to explore past the asteroid belt so far?

[brahmanknight]

?

[nacnud]

It hasn’t.

[Svetoslav]

Okay, if we exclude Rosetta, if we exclude Huygens landing on Titan (which has been conducted by an European probe) ... we should better paraphrase the question as : why is the USA the only country that was able to explore the planets beyond Jupiter with a national mission?

There is a good answer:

The USSR ( later Russia ) was never able to advance in the field of microelectronics as much as the USA. Remember the Mars 4-5-6-7 failures due to bad transistors? Remember how the triple-redundant computer of the Phobos probe gradually stopped working in late 80s? Soviet computers were always inferior compared to the western computers. Russian satellites work for months, maximum several years. American satellites work for decades.

That's why the USSR never attempted to send a probe beyond the asteroid belt. It would have never worked that long and reliably.

As for the other countries like India and China - their space programs are too young or slow. China and India are too focused on the Moon right now. Looks like China is already capable of creating long-working space probes, remember Chang'e 2? And they'll eventually send a mission to Jupiter, that's already in their plans, but it will take time.

[DreamyPickle]

This is an interesting question.

One aspect is that nuclear power sources are required which only the US and Soviet Union have historically flown. It's only recently that a solar-powered probe has made it to Jupiter.

Another issue is the extremely high delta-V requirement. The Voyager probes used the hydrolox Centaur upper stage which has no Soviet equivalent. I don't know the performance of Proton or Zenit to high C3 trajectories but based on their fuels it's likely pretty bad.

It hasn’t.

What are you referring to? Only flown non-US probe that I can think of is Huygens but that was a collaboration with the US.

[Durham Park]

An awfully lazy quick look at Wikipedia gives Ulysses, Galileo and Cassini but they are all indeed European collaborations with NASA.

[Robotbeat]

RTGs are a big one. It’s a unique capability that only the US and Russia have really had for terrestrial uses and only the US made a normal part of space operations. Another is cost you benefit ratio. The US space program is better funded than any other, meaning we not only send missions to the nearest planets but also further and further away from Earth.

Also, long-lived vacuum and space-rated electronics were not a thing the Russians/Soviets had until recently. They mostly rely on electronics in sealed, pressurized canisters. These tend to not last as long in space, and missions to outer planets could take years or even decades. So even if the Russians had big rockets, terrestrial RTGs, and a moderately funded space program, they never got beyond Mars for space missions and even for Mars had extremely poor luck.

And it’s true that Russian rockets tend not to use hydrolox, meaning their high c3 payload are small compared to the lift-off mass, they have compensated by using many, many stages (which contributed to the low launch reliability). Another reason for lots of stages, besides the lower Isp, is the higher tank dry mass of many Soviet rocket stages. The US used balloon tanks and such to get extremely good tank mass, which reduces the need to stage as often. This is why the two stage Falcon 9 can actually get pretty good performance to even fairly high energy trajectories. (The one area the Russians maintain a performance advantage is staged combustion engines… they get good T/W and high Isp for a given propellant, compensating a bit for high tank mass and not using hydrolox much… of course, Atlas V, which has become a workhorse of deep space missions, used Russian engines for the first stage… and I have to point out that Delta II was a deep space workhorse for years in spite of not using balloon tanks or hydrolox… it just used lots of stages like the Russian vehicles).

tl;dr: US had perfected in-space RTGs and long-lived space electronics, has more reliable rockets to higher energy, and importantly, more money than all the other robotic space probe programs combined.

[jebbo]

On RTGs, for Esa, this seems to be the state of the art:

https://link.springer.com/article/10.1007/s11214-019-0623-9

So, flight design by ~2025 ready for missions ~2030

--- Tony

[deadman1204]

A few reasons:

1. It takes ALOT more money. NASA is better funded than any other space program in the world.

2. Mostly requires RTGs. That limits things to countries with plutonium.

3. It takes really big rockets that not everyone has

4. It takes alot of tech. Russia has languished for decades, and china has basically stolen most of their stuff from russia (their rockets are remarkably similar to Russian rockets.... very much so) or the US (see jpl hack of 2018 where they stole all our data on landing crafts on mars).

[Vahe231991]

A few reasons:

1. It takes ALOT more money. NASA is better funded than any other space program in the world.

2. Mostly requires RTGs. That limits things to countries with plutonium.

3. It takes really big rockets that not everyone has

4. It takes alot of tech. Russia has languished for decades, and china has basically stolen most of their stuff from russia (their rockets are remarkably similar to Russian rockets.... very much so) or the US (see jpl hack of 2018 where they stole all our data on landing crafts on mars).

The Chinese have proposed two spacecraft capable of traveling past the asteroid belt, the Gan De and Interstellar Express. For now, these are design studies only, as financing development of these spacecraft requires not just the help of the China National Space Administration but also Chinese state-run energy companies that invest in uranium deposits and manufacture the components essential for interplanetary missions.

[RoadWithoutEnd]

In addition to everything already mentioned, I would bring up JPL.  There is an immense but incalculable value in institutional competence, and JPL has that in spades when it comes to crazy deep space technology that seemingly lasts forever.  If NASA didn't have JPL, the historical playing field in probes might be more level.

The details aren't very enlightening, but basically prove the value of a university / government lab partnership for doing the impossible.  And for whatever reason, JPL / Caltech ended up being profoundly and consistently productive while other partnerships were less frequent and less consistent.

[Jim]

  If NASA didn't have JPL, the historical playing field in probes might be more level.

Goddard and APL could have taken up the slack.

[libra]

  If NASA didn't have JPL, the historical playing field in probes might be more level.

Goddard and APL could have taken up the slack.

And Ames with Pioneer. Perhaps Langley, too - they played a major role in Viking.

[Jim]

 Perhaps Langley, too - they played a major role in Viking.

And Lunar Orbiter

[RoadWithoutEnd]

  If NASA didn't have JPL, the historical playing field in probes might be more level.

Goddard and APL could have taken up the slack.

Maybe, but JPL's achievements are crazy even compared to the other greats in probe work.  NASA hit the jackpot there.  Not to get sentimental, but it seems like JPL is where the spirit of Apollo retreated to when politics betrayed human spaceflight, and still shines very bright there.

JPL's motto, "Dare Mighty Things," gives me goosebumps because they actually mean it. 

I don't think the Soviets ever discovered that kind of institutional asset in their program.  They were more practical, less obsessed with the dream of it all.  And the outer solar system is definitely Dreamland from a practical space perspective, demanding a maximum of technical vision with a minimum of concrete return.

Beyond pure science, the main benefits of outer planet exploration are (so far) spiritual.  Those images speak to us on levels that are hard to justify in economic or security terms, and accomplishments in nearer space were winning much greater prestige on shorter timelines.

[janerampl]

I believe this is due to the fact that NASA is not so corrupted and deteriorated as the Russian space program is. The Russians could have done this before everyone else, but the political factors are hard to disregard. 

[Eric Hedman]

Also the will to do it with interest from both sides of the aisle is a big factor.  When Richard Nixon was asked to support the Grand tour mission with the rare alignment of the outer planets, he was so interested he asked why not send two spacecraft instead of one and we got Voyager 1 and 2.  This kind of science has interested all kinds of people with influence across the country.  That provides the will to do it.

[MATTBLAK]

Stole or copied? It may not be a difference with much distinction; but it is a difference.

[daedalus1]

ESA JUICE is soon. Jupiter orbiter and Ganymede orbiter.

[Proponent]

When Richard Nixon was asked to support the Grand tour mission with the rare alignment of the outer planets, he was so interested he asked why not send two spacecraft instead of one and we got Voyager 1 and 2.

Could I ask what the source is for that statement? Among the reasons for my implied skepticism are that 1) in that era it was routine to launch two spacecraft into each launch window (e.g., Mariners 8 & 9), and 2) the Grand Tour as originally proposed was never actually funded.  Rather, the scaled-back "Mariner Jupiter-Saturn" was renamed "Voyager."

[Proponent]

Goddard and APL could have taken up the slack.

And maybe Ames, too?  It ran Pioneers 10 & 11.

Outer-planet missions are cutting-edge stuff; I'd say the major reason the US has done so much more than the USSR/Russia is its much larger and more productive economy, which supports a substantially superior technological base.

I would further guess that the US might have accomplished even a bit more over in the past if JPL had had more competition from other centers.