NASA Mulls Missions To Neptune and Uranus, Using the Space Launch System

MarkWhittington writes: According to a story in Astronomy Magazine, NASA is contemplating sending flagship sized space probes to the so-called "ice giants" of Uranus and Neptune. These probes would orbit the two outer planets, similar to how Galileo orbited Jupiter and how Cassini currently orbits Saturn. The only time NASA has previously had a close encounter with either of these worlds was when Voyager 2 flew by Uranus in 1986 and then Neptune in 1989. Each of these missions would happen after the Europa Clipper, a flagship-class mission scheduled for the mid-2020s.

Comments

And the timeframe for getting another probe

[Rei]

... to Titan will be approximately three weeks after never :P

Well, at least they're not planning to follow up the wasteful 2020 flagship to Mars with yet another flagship to Mars as part of their ongoing Mars obsession at the cost of the rest of the solar system.

Re:And the timeframe for getting another probe

[Anonymous Coward]

Well, at least they're not planning to follow up the wasteful 2020 flagship to Mars with yet another flagship to Mars as part of their ongoing Mars obsession at the cost of the rest of the solar system.

While you seem to be one of those who sees those missions with disdain, there is a good logic for them.
1) Public favor. People got bored of the moon after a few visits, and Mars is the next most probe-able remote object to test probe tech on.
2) Theory testing. Mars probes have dealt with a fair deal of "that's interesting, but what about this other question?" that has lead to more advanced probes and rovers.

So, Mars is a good playground since they can't get funding to do live tests with major probes and landers on the moon anymore.

This logic is predicated on the assumption that NASA are logical and curious rather than being lead by a bunch of political appointees trying to manipulate the citizenry for votes. Or possibly "despite" instead of "rather than."

Re:And the timeframe for getting another probe

[Rei]

Mars is not the "next most probe-able remote object". Venus and Mercury have more frequent launch windows. And more abundant solar power. Capture is much easier at Venus, although surface survival is more difficult.

There are far more significant unanswered questions about bodies other than Mars that need "theory testing". Mars is the most studied body in the solar system outside of the Earth and the moon. And ranking the moon higher than Mars is at this point starting to get questionable. There are massive unanswered questions about many other bodies in the solar system. The incremental benefit for Mars is very low. Example: Venus is Earth's evil twin - such a close match for us in diameter and mass, formed right next to us, and yet it's a greenhouse hellscape without a magnetic field. We really don't know why. How much more of a fundamental geology question can you get than that? And as for fundamental biology questions, Titan is probably the best laboratory in the universe, while if the search is for actual extraterrestrial life, Enceladus probably gives you the best odds for your exploration dollar.

The public does not decide which NASA projects get funding, NASA does (except for a few big things mandated by congress). Nobody had a gun to their head and made them choose Mars 2020 or all of the others. In fact, with all of the craft we already have operating at Mars there's going to be a continuous stream of Mars news for the public for a long, long time. And really, what's been the biggest space stories of late, that show up say on the front page of Google News? New Horizons. Dawn. Rosetta. Cassini's latest flybies. The public likes pretty pictures and weird news, no matter where it comes from. And even congressional mandates these days are often for robotic probes to other worlds. When was the last time that congress mandated a probe to Mars like they did recently with the Europa probe mandate? They've insisted on general Mars policies, but nothing that specific in recent memory that I can recall.

Re:And the timeframe for getting another probe

[bananaquackmoo]

Maybe to you, but not to me.

Re:And the timeframe for getting another probe

[Coren22]

So, you are saying we should defund SNAP and put the money towards NASA? I can get behind that.

Fixing the problems on this planet will never stop, there will always be problems on this planet that need to be solved. No matter how much money you throw at it, poverty will exist until we have no scarcity. There are people who just don't understand how to not be poor, unless we decide to take over administrative control of their life, which we as a free society frown on. These are the same people on assistance programs that go out and buy a brand new iPhone, you can't teach these people to spend their money more wisely no matter how much funding you throw at it.

Re:And the timeframe for getting another probe

[Anonymous Coward]

Mars is not the "next most probe-able remote object". Venus and Mercury...

Excuse me, I shouldn't have laughed. Ahem. Mercury has the highest delta-v requirement amongst the planets. (Strictly speaking, Neptune may well be harder depending on the launch window.)

Re:And the timeframe for getting another probe

[Rei]

Excuse me, I shouldn't have laughed. Ahem. Mercury has the highest delta-v requirement amongst the planets.

Which would have been a great response, had I written:

Venus and Mercury have the lowest delta-V requirements

Which is, of course, NOT what I wrote. What I actually wrote was:

Venus and Mercury have more frequent launch windows.

Moving on...

With Mercury you can't save energy by aerocapture, but you can make very frequent flybys of Venus and Mercury to lose velocity - and making observations of both Venus and Mercury during each flyby. Messenger, for example, was launched in August 2004. It did an Earth flyby 1 year later, a Venus flyby 12 months later, then a Mercury flyby 15 months later, then 3 years later, orbital insertion. Now, that was a long time to orbital insertion, but not a long time before the collection of first data - it did minor data collection at Earth, more at Venus, and more during its first Mercury flyby. But more to the point, it was done with a tiny delta-V budget: 316m/s from Earth escape to Mercury insertion and 862m/s for the orbital insertion itself. Mars takes about 390 m/s from Earth escape to Mars transfer, 670 m/s for Mars transfer to Mars capture (if you can't aerocapture), and entering a similar orbit on Mars would take somewhere in the ballpark of 2000 m/s (5000 m/s to low orbit) (again, possibly reduced if you can aerobrake). While it's technically possible to use an Earth gravity assist to Mars, it takes much longer.

Now, of course, one could have used a more Mars-like delta-V to get to Mercury much faster, although due to the complexities of gravitational assists I can't work out readily here just how long it would take. But for Venus it's easy: 280 m/s from Earth to Venus transfer and then... well, aerocapture is pretty much a given if you want to (far easier than on Mars), but if you don't want to do it, then it's another 360 m/s to high orbit, then 2900 m/s to low orbit. But of course, Venus is a very easy body to aerocapture at, so it should be expected. Short transfer times to Venus, little energy to get there, easy to brake at, and frequent launch windows. How is that not more "probe-able"?

Re:And the timeframe for getting another probe

[Nethemas the Great]

Both Mercury and Venus have very nasty environments with which to deal with. Yes, they have launch intervals at tight intervals, yes there's an atmosphere to bleed delta-v, but at the same time a Venus rover would require comparatively huge engineering and material science investment, Mercury is a similar story unless hiding in a permanently shadowed crater is your only interest. Mars is a most excellent place to work out plenty of the other engineering challenges involved with such tools before we throw hostile environments into the mix.

Re:And the timeframe for getting another probe

[Nethemas the Great]

err... launch windows at tight intervals

Re:And the timeframe for getting another probe

[squiggleslash]

ASTRONOMER FIGHT!

(Imagines two bespectacled old men in white coats taking terms to bash each other over the head with large hand held telescopes)

Re:And the timeframe for getting another probe

[Rei]

Venus has an incredibly hospitable environment... in the cloudtops. Vastly more hospitable than the surface of Mars. And with how little we know about Venus, even something that doesn't land could completely revolutionize our understanding of the planet.

A higher budget mission could use a ballooning lander that makes repeated descents to the surface, then rises to recharge its batteries and let its coolant chill back down. Wherein it would be far more of a "rover" than anything we have ever sent to Mars - it could explore the whole planet.

Re:And the timeframe for getting another probe

[Rei]

Please, you two, please! Settle this like scientists! ;)

Re:Flagship-sized probe to Uranus?

[Rei]

Herschel, its discoverer, wanted to name it "George". ;)

Really, Uranus was a naming mistake - in keeping with the names of the other planets, it should have been named Caelus.

Ehh

[Intrepid imaginaut]

What size is a flagship?

Re:Ehh

[swb]

In naval parlance, Wikipedia defines it as:

A flagship is a vessel used by the commanding officer of a group of naval ships, reflecting the custom of its commander, characteristically a flag officer, flying a distinguishing flag. Used more loosely, it is the lead ship in a fleet of vessels, typically the first, largest, fastest, most heavily armed, or best known.

I've seen it used in automotive contexts where it seems to have a similar meaning -- I've heard the Mercedes S600 referred to as the "flagship sedan".

Since they won't be sending weapons or any admirals to those planets, I'm guessing that it will mean the biggest probe they can afford.

Re:Ehh

[Intrepid imaginaut]

Yes I know what a flagship is, the summary should read "flagship space probes" like the aticle does since flagships aren't, to my knowledge, of a uniform size.

Re:Ehh

[Rei]

Flagship is a technical term. NASA missions are divided into categories: Discovery, New Frontiers, Explorer, and Flagship. Flagship are the most expensive, and most infrequently launched. Flagship missions cost over a billion dollars, usually $2-3B. Because they're so expensive and infrequently launched, one expects a huge scientific return out of them - for example, although Cassini-Huygens cost $3.26B, it's returned such a treasure trove of data and incredible discoveries about the Saturn system that I doubt anyone would say it's not worth it. Is Mars 2020 going to return anything that worthwhile? Not even close. The sort of scientific territory it's exploring is far too well tread already; it's exploring small details, not huge unanswered questions. The Uranus or Neptune probes may or may not prove to be worth their price tag, but at least they stand a better chance. I know a lot of people for example itching to find out more about Triton after Voyager's tease, which was conducted with 1970s tech.

What's "flagship sized"? Did someone make that up?

[wonkey_monkey]

NASA is contemplating sending flagship sized space probes

Is the "flagship" the S.I. unit for space probe size?

Is it going to be this big?

After 2020?

[NMBob]

Give the contracts to the folks that built and flew New Horizons to Pluto. We'll be there next week and everything will work perfectly. Those folks did a great job.

Re:After 2020?

[Octorian]

You do know that New Horizons took nearly 10 years to get to Pluto, right?

Re:After 2020?

[rubycodez]

You article tells me it's possible to get to Pluto in under five hours

Re:What's "flagship sized"? Did someone make that

[Anonymous Coward]

Indeed, "Flagship class" refers to NASA's Flagship Program and doesn't say anything about the probe size. Given the need to carry a braking thruster all the way to the destination, I dare say that the actual payloads will be relatively small.

Re:Flagship-sized probe to Uranus?

[Chris Mattern]

Herschel, its discoverer, wanted to name it "George". ;)

And he wanted to love him and hold him and squeeze him and pet him...

Use RTGs for ion propulsion then comm.

[wisebabo]

NASA's needs Pu to get to Uranus (puns intended). If they can manage to get the correct isotope of Plutonium then a space probe that uses ion propulsion would have the necessary electrical power to drive the extremely efficient drive even when, as in this case, it is very far from the sun. Since the space probe DAWN has proven that multi-year thrusting of ion engines does work quite well, this would enable a "flagship" (read "big") mission to get to the very outer planets in less than a decade. It could spend roughly half its time accelerating to a high cruising speed then almost as long decelerating to be captured into orbit.

Then, once the mothership has arrived in orbit then, like Cassini, smaller spacecraft could be employed to explore the various moons and atmosphere of these gas giants. (Unfortunately since the moons of Uranus and Neptune may not be large enough to effectively permit gravity assists like Cassini uses with Titan or Galileo used with the four large Galilean moons, you might need smaller probes because the ion drive may have too low a thrust for dynamic orbital changes). Now the RTGs, having powered the spacecraft to the far reaches of the solar system, could be "gainfully" (ha ha) employed to power a high bandwidth radio transmitter/laser communicator. This would enable the small probes exploring the system to send lots of data back to earth without each carrying a huge antenna, only the mothership.

Why all spacecraft don't utilize the extremely high energy/weight RTGs for deep space PROPULSION is beyond me. I (maybe mistakenly?) think that the RTGs, since it generates its power from the natural decay of a radioactive element, is constantly "on" and if you don't use the power being generated YOU LOSE IT (anyone please correct me if I'm wrong!). So it would seem to be ideal for a space probe that needs to go somewhere far far away from the sun and for which a low thrust high impulse drive (like ion propulsion) that requires large amounts of electric power is ideal. Maybe it's because the DAWN probe needed to prove the ion technology before NASA could commit a flagship mission to it.

Too bad that the isotope of Pu that they need for the probe isn't the same that is used in nuclear bombs, that would be the most apt fulfillment of the biblical(?) phrase "beating swords into plowshares". Oh well, Congress needs to fund the reactor that is used in the nuclear fuel cycle that manufactures this critical resource for space travel.

Of course this is only a stopgap until we get either the Lockheed Martin or MIT (mini) fusion reactors working!

Re:Use RTGs for ion propulsion then comm.

[Cassini2]

RTGs are being phased out because (a) the probes need more power than ever with modern computers, and (b) because of environmental concerns. Unfortunately, most of the environmental concerns revolve around the word "Plutonium" and the much more dangerous Plutonium-239.

The best RTGs use a chemically locked Plutonium-238 Oxide that is probably one of the safest fuel sources ever invented. The stuff is non-reactive ceramic that is almost indestructible, and is readily rejected by the human body if ingested. It's not even particularly radioactive, as radio-active isotopes go, because to make the RTG last for a long period of time, it is necessary to use an isotope with a sufficiently long-lived half-life characteristic. Plutonium-238 Oxide is the polar opposite of the more typical dangers from Plutonium-239 that everyone worries about.

See RTG generators and plutonium oxide for more information.

Re:Use RTGs for ion propulsion then comm.

[Megane]

You could also use solar power for ion engines, but that barely gets you to the asteroids before you run out of sunlight (Jupiter gets what, 4% the sunlight of Earth?), not to mention the amount of reaction mass needed. It would work great for the inner solar system, though.

Re:Use RTGs for ion propulsion then comm.

[Rei]

Why all spacecraft don't utilize the extremely high energy/weight RTGs for deep space PROPULSION is beyond me

First off, even with the little we use today, we already have a serious shortage of it. At least funding has been reestablished to produce more. But production rates are going to be very slow and expensive, and this means that the fuel will continue to be expensive. Unfortunately, 238Pu needs to be thought of as a manufactured product, not a waste product. It's impractical to extract from nuclear waste - you have to first separate out neptunium (which isn't too common to begin with, which means lots of reprocessing, which is expensive), and then you have to bombard it with a lot of neutron flux for a long time (neutron flux being very valuable, as it's what you can use to make power (by bombarding a fissile target) or medical/ industrial isotopes). And you need a lot of plutonium to be useful for space probes (kilograms), not the sort of ng/ug/mg quantities usually used in medicine and industry.

The net result is that RTGs are almost always the best option from Saturn on out, usually the best option for Jupiter, sometimes the best option for Mars and the asteroid belt, and seldom for Earth on inwards.

Re:Use RTGs for ion propulsion then comm.

[Rei]

1) RTGs are not being "phased out". They're actually going to become more common in the coming years, now that 238Pu production has restarted.
2) Computer power consumption has dropped, not increased.
3) For outer planetary missions, there is literally no better solution to produce X number of watts, whatever number X may be (up until you get into the many-dozens-of-kilowatts range, where it probably pays to start developing an outright fission reactor)
4) Few people would consider 238Pu to have a "long half life". There are certainly things that it's long in comparison to, but as far as "long lived radioactive" products are considered, it's not even close to being considered one.
5) Plutonium is not "rejected by the human body", it's accumulated in the bones, and alpha radiation inside the body has 20 times the destructive power of beta and gamma per MeV (also, with beta decay, 2/3rds of the energy is usually lost as a muon antineutrino)

Note: Please don't misinterpret this, I'm pro-RTGs. I just wanted to correct the facts.

Re:Use RTGs for ion propulsion then comm.

[Rei]

1) There's nothing to make staging any harder for ion craft than for chemically-fuelled craft

2) Dawn's ISP has a max of 3100sec. There's plenty of room to be improved.

3) A probe at a gas giant (or moon with an atmosphere, such as Titan) could potentially orbit through the exosphere, scooping up new propellant. While that would be no insignificant engineering work, there's nothing making it impossible. The relative velocity of the ions it'd be scooping are far lower than the exhaust velocity of a good ion engine, meaning that it could compensate for the drag by thrusting with only a small fraction of the propellant that it collects. And most ion engines are very propellant-choice flexible - they don't have to use xenon, and it's not a huge penalty to use other gases. So such a probe could leave orbit and even return to Earth. As a bonus, any leftover propellant upon arriving at Earth would be a sample return.

My personal dream mission is something akin to #3 for Titan, with a VTOL rotary-nacelle lander carried along for the ride - the orbiter being its "tugboat" and communications relay. A one-year mission at Titan with realistic flight speeds and recharge times should allow such a lander to go to pretty much everywhere interesting on the moon. If the probe's payload was sufficient, the VTOL lander could be supplemented by an ascent stage (my calculations show that something like a scaled down Pegasus upper stage should be sufficient, and its propellant mix appears to tolerate cryogenic conditions), so you'd get small surface samples from all over Titan returned as well. And if you have a probe in the Saturnian system with an atmospheric scoop, you might as well do a Stardust-style aerogel flyby of Enceladus and scoop a bit of Saturn's exosphere on the way back - the mass penalty required for adding both to the mission is trivial. An Enceladus flyby needs a sheet of carbon aerogel with a closable shield (if desired, the impact velocity could be kept low if desired by entering into a Molniya-style Enceladus orbit, having near zero velocity high over the plumes). A Saturn scoop needs a tiny additional tank and valve so that its sample doesn't get mixed in with the bulk gas taken from Titan.

Seriously, the potential scientific value of all of those sample returns would be almost unimaginable. We don't even know what tholins are as things stand, and yet they may have been the progenitor to life on Earth. And there's always the chance that signs of actual life, past or present, would be found in Titan or Enceladus samples.

There's of course a lot of engineering work (which means unknowns, which means risk) in such a mission. So it would be wonderful if they could retire part of those unknowns by testing out propellant scooping at Uranus or Neptune.

Re:Use RTGs for ion propulsion then comm.

[Rei]

First off, you say "dust lodged in the lungs" as if that's a good thing. It's an intensive alpha emitter. Check out how miniscule of quantities of radon (another alpha emitter) it takes to pose a health threat. But yes, most plutonium dioxide ingested in that form passes through (not without irradiating the digestive tract first, of course); the ingestion route is more hazardous for more soluble forms of plutonium.

Re:Use RTGs for ion propulsion then comm.

[Xyrus]

Very Kerbal. Much wow.

The problem with RTGs is that the contain the word "nuclear" in their description. This induces hysterics in the idiotic population that a mishap will result in an Earth Shattering Kaboom(tm).

I blame Marvin the Martion for this.

Re:Use RTGs for ion propulsion then comm.

[electrosoccertux]

rocket...tropelled...grenades...

hm..,no....thta's not right....whatever...it's too late to google

Re:Finally a mission for SLS

[Megane]

...and the rocket that was supposed to get American astronauts back into space... now has unmanned planetary probes as its main missions. Score another one for ATK!

Re:Fast Launch Cost

[oh_my_080980980]

There's no one who thinks what you said makes sense. Seriously. No one.

Re:neptune and uranus?! what on earth for?

[oh_my_080980980]

RTFA:

"Neptune’s moon Triton is an enticing option for many of the same reasons that prompted the Europa Clipper mission. No other large moon in the solar system has a retrograde orbit. That leads astronomers to suspect Triton is actually a captured Kuiper Belt object — a larger cousin to Pluto. Triton is also nearly as big as Earth’s Moon but has smoke-stack like plumes from ice volcanoes that erupt nitrogen frost onto its surface. "

Re:Stop justifying SLS already, use many launchers

[WindBourne]

it is for that reason why a rocket company would be smart to develop their own tug/fuel depot on their dime.
Basically, build several sizes of tugs that have a common interface. In fact, LIDs while being big, would be ideal.
That would make it cheap to hook up to various sats, as well as Bigelow, ISS, tools, etc.

Who is really missing the boat on this would be rocketdyne since they have engines, but do not have active systems.
Another one would be Blue Origin. they have the money and the engines.

Re:What's "flagship sized"? Did someone make that

[Coren22]

Personally, I would love to see NASA come out with one this size:

https://en.wikipedia.org/wiki/...

I think that was a flagship...its arms could be classed as flagships.

Re:Flagship-sized probe to Uranus?

[bkmoore]

Like, does it take a flagship to search for Klingons?

Yes because it's a five-year mission: to explore strange new worlds, to seek out new life and new civilizations, to boldly go where no man has gone before.

Re:Flagship-sized probe to Uranus?

[rubycodez]

you sure have matters licked

Re:NASA needs more Antarctica defense money

[dargaud]

I used to find those kinds of posts funny, but now I just want the troll gone because there's always some kind of idiot who will copy it on facebook or other "I read it on the intharnet"

Finally, Capt. Obvious

[bzipitidoo]

Sending orbiters to Uranus and Neptune has only been the most blindingly obvious next step in space exploration for at least 20 years. Why does Jupiter rate a second orbital mission (Juno) before either of Uranus or Neptune have had one?

Retrieves Popcorn...

[trooper9]

This is gonna be awesome.

Re:Flagship-sized probe to Uranus?

[tehcyder]

This topic just screams for some juvenile humor...

There is a sense of humour blindspot on slashdot about Uranus. I can only assume it is a bit of a sore spot.

Why Mars [Re:And the timeframe for getting anoth

[Tablizer]

Mars has been explored heavily because a manned Mars mission (MMM) has been in planning since W announced the project during his term. True, the funding for MMM has been waxing and waning, but so far the plan is still alive (even if sick).

It makes sense to probe Mars heavily before a MMM. For one, the question of past or existing life has yet to be answered. If there is life on Mars, that will greatly affect how a MMM is done.