Deep Space and Interplanetary Exploration - The Universe is Timeless

[kato]

Current state of active interplanetary probes (other than Mars, Mars is boring):

Rosetta : Keeps bumbling around 69P/C-G. Hit safe mode again last week 5 km from the comet, same reason as last time. Team has announced final landing operation - planned for September - will be detailed "soon".

Juno : Woken up and testing its equipment before insertion into Jupiter orbit next month. Not much to report.

Akatsuki : Orbit adapted for continued operations in Venus orbit until 2020 now.

Cassini : On revolution 236 around Saturn, T-120 Titan flyby just went by as normal yesterday. Tour schedule for the rest of the mission - until mid-september 2017 - has been announced, and includes (from today) 173 planned moon flybys; however only 6 will be "close", all at Titan, and in total only 16 other moons will be covered. Of the seven large moons in the system Rhea, Iapetus and Dione won't be visited.

Dawn : Photographing Ceres. Still. They're trying to extend the mission until early 2017 it seems.

Hayabusa 2 : Enroute to Ryugu. Should arrive in two years.

New Horizons : On course for 2014 MU69. Still sending data from the Pluto flyby.

Voyager 1 and Voyager 2 : Interstellar medium yaddayadda. Voyager 2 should - by NASA estimates - lose capability for gyro operations this year, Voyager 1 next year. NASA hopes to keep both still sending data till 2020-2025, but the gyro loss indirectly affects accuracy in craft-to-earth communications, and hence may mean a loss of signal at virtually any time afterwards.

[Daryk]

Interesting, i don't know if is wishful thinking by Space.com and person came up with it.

Asteroid Seed Ship, aka convert a Riod into a ship.  I think it's bit of a stretch. Not i think it's not possible but i think its stretch.

A stretch it might be, but it sure looks like a way to get Mars' mass high enough to hold a proper atmosphere with a minimum of expense.

[ANS Kamas P81]

Iapetus won't be visited.

Don't want to risk showing off that curious object in the middle of the white side.

[worktroll]

Rhea, Iapetus and Dione won't be visited.

"All these worlds are yours ... except those ones. Attempt no landing there."

[kato]

The moons to be photographed are:

- ring gap moons : Daphnis, Atlas, Pan, Prometheus, Pandora
- inner moons : Epimetheus, Janus, Helene, Polydeuces, Tethys, Telesto, Mimas, Enceladus, Pallene and Methone

Of these two groups only Calypso, Dione, Aegaeon and Anthe won't be flown by. Of the outer moons beyond that, only Titan will get visits. About 30 in total, also given that Cassini uses it for orbit control.

Only relatively close flyby planned for this year will be one at Pandora at 13,800 km distance - offhand the best pictures taken so far were from 52,000 km. Titan gets another 1,000 km flyby next month, a couple below 2,000 km, and Cassini will then switch to 3,000+ for next year to better explore the F ring.

Of those not flown by, both Rhea and Dione will instead have occultation observations this year, with Cassini's ultraviolet imager checking for atmospheres while they pass in front of a star.

So I guess... Iapetus is indeed the odd man out.

[Weirdo]

Crap on a cryogenic cracker, Cassini gets around! Did they give it ginormous fuel tanks for orbital adjustments, or is this a case of truly epic flight planning?

[kato]

There's just a ton of rocks out there in its way ;)

Realistically, Cassini is on an elliptic inclined orbit, which means that on each orbit it always passes somewhere between the inner moons at its perigee and it always passes through the ring plane twice per orbit (going through the gaps). Flybys of the outer moons are mostly "targeted" and require orbit adjustments; about half of Cassini's orbits did not match the current regime, but put it in place for e.g. Enceladus, Rhea etc. Cassini previously perfomed such moon encounter regimes in which it mostly orbited within the equatorial plane. The current regime simply bumples Cassini between the back side of Titan at apogee and the opposite side of Saturn at perigee, with flybys of the other large moons being more coincidental when they happen to be close. Most of the planned flybys are "distant flybys" at around 60,000 to 120,000 km. The intention behind the current regime is to (massively) increase inclination through gravity assists at Titan, so that half the orbit is now spent considerably "above" the equatorial plane and the other half considerably "below" it - Saturn therefore looked like this for Cassini in April when it was "above".

Going by dry mass percentage the fuel tanks are about on par with Rosetta. Then again Cassini did not have to play catch with a comet.
What Cassini does have in comparison to others is time. Endurance. With the mission extension it's currently on Cassini will have performed 293 orbits of Saturn before it is intentionally dumped into the atmosphere. Juno for example will only get 33 orbits at Jupiter.

[worktroll]

Presumably it can also make orbital changes by small maneuvers at apogee (aposaturn?) - not like it has to match delta vee with different moons.

Still, seriously great stuff!

[kato]

(aposaturn?)

Apokrone (from Cronos) or in a slightly more vulgar pinch -saturnium, although -apsis is always fine. -gee is only used with Earth.

[rebs]

Ancient linguistic roots for terms our ancestors of yore could not have properly imagined... without help from a monolith.

snip

[cray]

Pluto pics of the day: where the flatlands' nitrogen ice crashes against the water ice mountains.

https://solarsystem.nasa.gov/galleries/the-jagged-shores-of-plutos-highlands

[rebs]

Thank you for bringing that to our attention.  New Horizons was worth every penny put into the mission.  The resolution of these pics we've received and will keep receiving blows my mind.

[kato]

Should have instead sent it to become a Uranus orbiter, like one project is currently proposing with the flight spare body of New Horizons (with internals being flight spares of Cassini, MER and Rosetta - like New Horizons, just in different config). Currently NASA exploration flagship priority 3, after Mars 2020 and Europa Clipper.

[worktroll]

The energetics involved ... ugh. Anything fast enough to get there in a useful timescale - remember how long it took New Horizons, or Cassini - would need massive delta-vee to then go into orbit.

As much as I'd love trans-Saturnian orbit missions, I'll wait for a drive tech breakthrough.

W.

[BirdofPrey]

We need more probes designed to utilize areocapture.

Also, I am waiting for someone to send a blimp probe to venus

[Lazarus Jaguar]

As much as I'd love trans-Saturnian orbit missions, I'll wait for a drive tech breakthrough.

W.

I'll keep saying it.  We Need Orion!

[kato]

Anything fast enough to get there in a useful timescale - remember how long it took New Horizons, or Cassini - would need massive delta-vee to then go into orbit.

Proposed flight times are 12.8 years if sent on an Atlas with gravity assists and SEP and about 8 years for the direct route utilizing SLS.

[ANS Kamas P81]

Proposed flight times are 12.8 years if sent on an Atlas with gravity assists and SEP and about 8 years for the direct route utilizing SLS.

Is that with a flyby velocity, or slow enough for orbital injection?  Remember it took Cassini SEVEN years to get to Saturn, and not go too fast that she couldn't slow down in time and sail off into the deep.  Uranus is literally twice as far as it is to Saturn, and has 1/6 the mass - any proper orbits around that planet are going to be closer and even slower than Saturn's, which means you're still flying over twice as far (2.7 billion km instead of 1.2) and now have to travel at a lower speed for the target orbital velocity - which for Cassini is right around 5.4km/s.  Your target velocity will be lower than that at Uranus; just to pick a number Luna orbits around Earth at just over 1km/s.  It's safe to say that "between these figures" will get you a suitable orbit to go swing around the planet and buzz the moons.

Cassini really is one hell of a program with a success that shouldn't be overlooked.

[kato]

That's with orbital injection. There's a study on trajectories here: http://www.lpi.usra.edu/opag/meetings/aug2015/posters/6-UranusTrajStudy_Hughes_et_al.pdf
New Horizons and by deference the Uranus Orbiter using the same frame would be a lot smaller than Cassini btw. About one-quarter in dry mass. The trajectories computed above allow for at least 60% fuel, about equal to Cassini.

An orbiter at Uranus wouldn't focus on the moons btw, especially since any probe launched from Earth would enter a polar orbit around Uranus - Uranus' axis is tilted nearly 98° to the solar ecliptic and the moons are coplanar to it. Moon flybys can therefore only occur at most twice per orbit.

[rebs]

Proposed flight times are 12.8 years if sent on an Atlas with gravity assists and SEP and about 8 years for the direct route utilizing SLS.

Yes, SLS is the great hope.  I pray the NASA political footballs stop being punted long enough for it to become reality.

[ANS Kamas P81]

An orbiter at Uranus wouldn't focus on the moons btw, especially since any probe launched from Earth would enter a polar orbit around Uranus - Uranus' axis is tilted nearly 98° to the solar ecliptic and the moons are coplanar to it. Moon flybys can therefore only occur at most twice per orbit.

Sure it could.  As you approach Uranus, you're relatively close to its orbital path. Instead of staying within the general ecliptic, simply aim "down" or "up" as you make your capture passes and you'll end up in a suitable orbit around the planet interfacing with the moons.  Just like the difference between a polar orbit and an equatorial orbit; you just make a different approach to be slug around in the right direction.

[kato]

Won't get a good look at the methane smog clouds around the south pole that way though. The moons are just a couple boring rocks like about fifty others around other planets that have already been looked at.

[ANS Kamas P81]

Won't get a good look at the methane smog clouds around the south pole that way though. The moons are just a couple boring rocks like about fifty others around other planets that have already been looked at.

An excellent point abut the methane clouds, but then again the solar system's just FULL of surprises...

[cray]

Won't get a good look at the methane smog clouds around the south pole that way though. The moons are just a couple boring rocks like about fifty others around other planets that have already been looked at.

People said Pluto was going to be boring, too. A dead ball of ice unchanged since the dawn of the solar system. ;)

Remember it took Cassini SEVEN years to get to Saturn, and not go too fast that she couldn't slow down in time and sail off into the deep.

Well, the Atlas V proposals for Uranus are suggesting twice the flight time as Cassini. ;)

But it's amazing what a few km/s here and there can do for flight times in space. You only need a few hundred m/s extra to cut the Earth-moon flight time from 3 days to 1 day, or about an extra 1000m/s round trip. A few extra km/s and suddenly Uranus is only 10 years away, or 8.

[worktroll]

We need more probes designed to utilize areocapture.

Aerocapture works best when relative velocities are relatively low. The higher the delta vee, the more ablative mass is needed. Also, you need pretty good figures on atmospheric density & composition against height, & be able to make good predictions over time (eg. the Martian atmosphere is denser in the summer hemisphere than the winter one, which gets CO2 freezing out on the winter polar cap). Not sure we have that much good data on the trans-Saturns.

The answer is of course to add more fuel for course corrections, which means more mass, which means more ablatives, and so on ad infinitum.

Great book - "The Atomic Rocket" - by the son of Freeman Dyson, covering Orion, makes the point that one of the problems finding a sponsor for the project was that - at the time, 1950s - no-one could think of a 'good reason' to be able to loft 10K tons into space ...  :'( :'( :'(

[kato]

What we need are shields. These shields:

https://www.nasa.gov/feature/magnetoshell-aerocapture-for-manned-missions-and-planetary-deep-space-orbiters/

(edit: link that actually works for me - http://msnwllc.com/Papers/Kirtley_MSNW_NIAC_12MAR_final.pdf )

[Natasha Kerensky]

Yes, SLS is the great hope.  I pray the NASA political footballs stop being punted long enough for it to become reality.

The next Administration will try to terminate SLS and not because of politics.

SLS (and Orion MPCV) flight safety projections are coming out worse than the Space Shuttle, which two prior Administrations terminated because of safety issues.

SLS can't do humans to Mars.  Its flight rate is nowhere near high enough to support the tonnage needed for NASA's own reference missions for human Mars expeditions. 

Congress just proposed terminating the Asteroid Retrieval Mission, the only other human target on the books for SLS besides Mars.

Multiple NASA, industry, and university studies show that SLS is not needed for human lunar missions, if the next Administration goes that route.

It costs more to use SLS than saved in shortened mission operations for robotic planetary missions.

SLS development schedule has slipped multiple years and development costs keep going up with no end in sight.

NASA has no handle on SLS's upper stage beyond the first demonstration launch.

Hundreds of millions of dollars and months of schedule have been lost to basic errors and bad management of ground facilities.

I could go on, but you get the idea.  FWIW...

[kato]

It costs more to use SLS than saved in shortened mission operations for robotic planetary missions.

Given that one calculates around 10 million per year for mission operations that is always a given (unless we're talking 150+ years saved when compared to Delta - arguably the case if we ever send something to Planet Nine, once we know whether it's out there...).

[ANS Kamas P81]

http://www.cnn.com/2016/06/15/health/nasa-cassini-saturn-ring-mysterious-activity/index.html

Well ****, the fithp are coming.

[worktroll]

Baby elephants wearing platform shoes under hangliders!