Does the gravity assist at jupiter cross within the 4 major moons?

No -- it's a short distance outside Callisto's orbit. Had it been launched in the previous window in Dec. 2004, it could have made a close flyby of Europa; had it been launched in the one before that in Nov. 2003, it could have made a close flyby of Io. Yet more lost as a result of Dan Goldin's idiocy.

I hope that Callisto is in that part of its orbit at the time.

Well, you can't deny the man did leave his mark upon space exploration! (Though not with the legacy he was hoping for I would imagine... )

Missing targeting opportunities like this are an almost unforgivable sin, especially on these "once per professional lifetime" type missions. Losing these fly bys means less science for the buck, an irony so glaring as to be obvious even to The Dan.

His Let's Give Murphy's Law A Head Start Program, also known as Better, Faster, Cheaper was directly at odds with choosing hi-profile PR one off missions. Decreased funding meant decreased testing and missed design flaws; leading to such innovative solutions as the Genesis probe's lithobraking and advances in deconvolving algorithms for imagery.

Perhaps I will start a Better Faster Cheaper rant topic elsewhere, I apologize for topic hijack.

And thanks again to Alan for visiting us and relating all the good news as it happens!

I have been following this forum (as well as ISSDG/Jupiter List and volcanopele's blog) for awhile now (great work by all!) and it's my first post.

The question I have is, re: NH - according to the paper on RH telecom design (DeBoy, C. C. et al. (2005). The New Horizons mission to Pluto: Advances in telecommunication system design. Acta Astronautica), the theoretical possiblity exists for NH to use both TWTA for downlink, resulting in a 44% reduction of downlinking time. Are there any concrete plans for such a capability to be used, esp. immediately after the encounter so that a larger browse dataset can be downlinked back?

Also, re: RALPH, has all the problems with the instrument been more or less dealt with (to a large extent)? I recall reading about LEISA having serious SNR/electronics problems during the optical tests, which when translated to the encouter, could have lead to fatal problems. Thanks!

Well, I have no objection to the "smaller and more frequent" part of "Better, Faster, Cheaper" -- since it means that you lose less from an individual failure due to a design flaw. (Mars Observer cost more than the next 4 US Mars missions combined.) Unfortunately, while this was a very good idea on Goldin's part, it seems to have been his ONLY good idea. (And its advent was probably inevitable at some point after the Challenger disaster had ruined NASA's earlier plans to require ALL US spacecraft to be launched on Shuttles, by the simple technique of making them too big to be launched on anything else.)

As for the Pluto probe: I learned at the 2000 meeting of the Solar System Exploration Subcommittee that he didn't want to fly it at all. All his repeated demands to go back and make the spacecraft even smaller than the last design team had made it were just his way of clandestinely killing it -- "Nobody gives a damn about Pluto", he told one aide. He was totally obsessed with astrobiology instead -- and while it remains my main reason (and that of a lot of other folks) for being interested in space exploration, he ran it into the ground.

hi Bruce, I think I had heard that story about Goldin and Pluto... amazing, really. I would be interested in hearing more about your take on some other bits if I can talk Doug into starting an exploration strategies topic...

I am just glad that he didn't succeed in stopping this mission, if that was his preference!

EDIT: (I started a Better Faster Cheaper topic over in EVA if anyone cares to join me... )

New Scientist has an interesting article this week about the possibility of a number of reasonably large unfound planets (total mass: sub-Mars) in the region between Pluto and the Oort Cloud. It describes a plausible explanation (the 'Oligarch' theory) for some of the more extreme orbital strangenesses out there, and gives some examples of search strategies etc.

My questions relate to this, and probably I'm hoping that Alan, or perhaps Bruce, can answer:

If an object is identified then what are the constraints on imaging it from New Horizons? At what point in the extended mission will images become impossible (I presume that we'll end up with some very low temperatures and a broken camera). By imaging, I mean anything up from a star-like dot - I'm not expecting pretty pictures!

I presume that if an object was identified before the Pluto encounter then the spacecraft might be retargetted, and that there would be a fair 'spread' of space which might be reached. However, if any sort of slingshot wasn't carried out (perhaps due to any putative body not being discovered in time, or a desire to maximise Pluto/Charon science, or (gasp!) no money) then what sort of maneuvering capability would New Horizons be likely to have by then? I expect that it'd be very slight, and hardly likely to allow much retargetting, but would just like to know for sure!

Bob,
Some good information at the NSSDC here... http://nssdc.gsfc.nasa.gov/database/Master...og?sc=NHORIZONS

"After passing by Pluto, New Horizons will be headed out to the Kuiper Belt where multiple Kuiper Belt Objects on the order of 50-100 km in diameter are expected to be targeted for encounter and similar measurements to those made at Pluto. This phase of the mission will last from 5 to 10 years. "

If they have the capability to image 50-100 kilometer objects, sub-Mars size objects should be a piece of cake. When they refer to "targeted", surely they must be talking visually only. By the time they reach Pluto, there won't be enough hydrazine left to do much of a course correction and flying 9600 kilometers at closest approach to Pluto won't allow for much of a gravity assist.
But it is big open space out there, and the sooner they spot something the more options they have.

Gary

We are hoping for a close encounter with at least one Kuiper Belt Object- we hope to have enough hydrazine after Pluto to target at least one small one. Small ones are easier to target simply because there are more of them so less of a course correction is likely to be needed to get to the closest one. We are currently conducting a search for suitable KBOs along our probable trajectory with the Subaru telescope on Mauna Kea. The KBO encounter is however dependent on having enough hydrazine, and we won't know till after launch whether we'll have the fuel to do it.

But the key is being able to get close with a targeted encounter, within ten thousand kilometers or so. We probably won't be able to do anything useful with large KBOs, except perhaps measuring their brightness at high phase angles, simply because they are few and far between and at our likely closest approach to any of them we still won't be able to compete with ground-based telescopes. Our telescope aperture of a few inches at a range of a few AU can't compete with a 10-meter terrestrial telescope 40 AU away.

Even if you still have half the hydrazine left after the encounter with Pluto, that would give you less than one degree of course correction. (If I did my math right)
And since the spacecraft at that point will be 2-1/2 degrees out of the plane of the solar system, wouldn't that make an encounter with a kbo fairly unlikely?

Gary

We've done the numbers and we have a decent chance of finding a KBO even within that narrow cone, and accounting for the latitude of the spacecraft. We simply have to chose one of the smaller, more abundant, objects.

Hurry up and launch it before someone decides Pluto isn't a planet any longer.

Question: is the final trajectory for the new horizons probe elliptical or hyperbolic? I would have thought that it would be going fast enough to escape (11km/s past pluto is faster than the 6.7km/s escape velocity I get for out there, at least if you're going mostly away from the sun at the time) but a slashdot article today is suggesting it will return to 1au in 50,000 years or so. So what's right?

Hmmm. I'm guessing SlashDot is wrong here. The SlashDot article has one sentence saying it will return, but I've never before heard that it isn't on an escape trajectory. The NH website doesn't even say what the flyby velocity of Pluto is, so there's no way to tell from that site. I've seen other places saying 11 km/sec for the flyby, but I don't know if this takes into account that Pluto is already travelling a few km/sec outbound as this mission is arriving well past preihelion for Pluto. The outbound velocity might be 13-16 km/sec.

I would imagine that NH would not end up returning to 1AU, since after the encounter with Jupiter, it will have a perihelion closer to five AU.

If the galaxy were not filled with gravitational knots (other stars), you might expect the Voyagers and Pioneers to return in 225 million years.

New Horizons is on a one-way trip, outward bound.

The planned trajectory is hyperbolic from the solar system. The flyby
speed at Pluto depends on the arrival year. For a 2006 Jan launch and a 2015 July arrival, it is about 13 km/sec.

-Alan

Are you saying that the Voyagers are *not* on hyperpolic trajectories?

Until these posts, I've always been under the impression that all four of the distant human spacecraft were travelling at above Solar escape velocity...

That 225 million years involves an orbit...around the galaxy

Doug

Doug:

That, I can accept!

And obviously, it'll be perturbed to hell and back by then, so Adios, Amigo!

Bob Shaw

Something different; I'm curious about how much fuel NH would have to take to be able to do a POI-burn. Probably a lot considering it's velocity.

Well, a low circular orbit of say, 100km around pluto would require...
umm

a=v^2/R f=MA f=gM1M2/R^2...

UMM

ahh

right

boil all that down and basically the orbital velocity of any spacecraft is....

Sqrt of G M1 / r

where G is newtons tiny number, M1 is the mass of the body ( pluto ) and r = radius from the centre of the body

I get 865 m/sec for an orbital velocity - so you'd have to have a delta V of 12.1km/sec - Consider MRO, which is 50% fuel by mass - and can manage a Delta V of about 1km/sec

Of course - if you broke into a very eliptical orbit - it would be less delta V than that - but that maths is beyond me

Doug

SO:

At roughly 400 kg's of (dry) mass, that would mean it has to descellerate roughly 20 % of MRO's mass....which will consume a fifth of 1100 kg's of fuel, being 220 kg's for each delta V of 1 km/s for NH.

Times 12,1 (or do i forget an exponent here ?) means 2660 kg's of hydrazine, which would make NH 3 tons in total.

I'll forget about it.

But then - at the beginning of that burn, you're having to decellerate 3 tons as well

It's called the rocket equation I believe, cant remember the specifics of it - but it's the equation that tells us that at launch, not only is a rocket launching it's payload, but it's launching all it's fuel as well - which gets consumed en route.
Put it this way - 12km/s is 60% MORE than the speed required to orbit the earth - and you have some very mighty rockets to start doing that

Doug

I knew i forgot about that while i was writing (you have to bring the fuel you need later on, which costs energy as well). But roughly we could say, that it would have to be an inverted delta II or something like that.

Why not brake gentle after jupiters assist with an ion thruster or something and ooze in orbit by just the right speed and angle ? Why do these OI burns always have to be so brute and violent just before passing the target ?

If you used an ion thruster it would add years to the mission. It has taken Hayabusa months to approach its target gently.

Nick

give a deceleration of 1 mN on 400kg - you've got an acceleration of 0.0000025 m/s^2

So the 12km/sec would take about 152 years

Doug

I wonder then how they'll manage to get the probe as described in the "far out" thread to 100 km/s with ion thrusters within a scientists lifetime. Stack em up probably !

Let's forget about orbitting Pluto. It's too expensive and way out of proportion. A flyby within my lifetime would be perfect for me: i am wondering about what it looks like there since i could read.

Keep in mind that for this scenario to work, NH would need to be on an elliptical orbit with a aphelion at Pluto's expected location. That would be a very slow journey.

What about a space-based launch? This'd assume a stable space station, like the ISS's descendant, and preferably one a bit higher than the ISS. Maybe a few launches of main modules, assemble in space, and send it on its way.
Even so, it'd need to be big (like, probably larger than Cassini), but at least the problem of a launch vehicle wouldn't be an issue.


That aside, I'd still love to strap an ion engine onto New Horizons and switch it on once the Pluto flyby is done. Fling the thing outta here fast.

The main problem with low-thrust orbiters for the really distant outer Solar System is that, after you thrust for a long time to get to the planet fast, you then have to thrust just as long to slow down the flyby speed enough to be able to brake into orbit around the planet when you get there. Unless, that is, you have a planet with a substantial atmosphere -- such as Uranus or Neptune -- in which case you can have the best of both worlds: use an ion drive to ram the probe into the outer Solar System rapidly, and then eject the ion-drive module just before arrival and use aerocapture to brake into orbit around the planet. Which, in fact, is exactly what JPL plans to do in its current Neptune Orbiter design.

You might, perhaps, be able to do that at Pluto, using a ballute, if you get there before the extremely thin atmosphere freezes out. (JPL is seriously considering adding a modest-sized Triton soft-lander to the Neptune Orbiter, having discovered that most of the lander's preliminary braking can be done by skimming through Triton's extremely thin air with a ballute that would be quite low-mass.) But in Pluto's case, there's a real chance that the air WILL have frozen out by the time you get there. In any case, the important thing to do with KBOs -- including Pluto -- is to examine as large an assortment of them as possible, rather than spending large amounts of money focusing on just one (even one as relatively distinctive as Pluto).

In fact, Pluto, unlike the other large KBOs we know, may suffer from the same problem Triton does, if to a lesser degree. Namely, it is a binary, and as such, tidal heating may have melted it enough that it is no longer truely representative of a primitive KBO.

It is considered unlikely that even the impact that broke off Charon (let alone the tidal effects afterwards) heated Pluto as much as Triton was heated. (It was probably a much slower-speed collision than the one that created our Moon.) But there may indeed be differences between Pluto and KBOs undamaged by collisions, albeit much smaller than the differences produced by the tidal heating that totally melted Triton -- and so, once again, a broad sample of KBOs is indeed important.

(Note that the 2002 Decadal Survey actually listed a survey of multiple KBOs as a MORE important scientific goal for New Horizons than studying Pluto specifically.)

The most extreme elliptical orbit with a perihades (?) of 100 km would be the orbital velocity you derive times sqrt(2) (minus a tiny pinch so it doesn't quite escape). That would thus save about 300 m/sec off the 12.1 km/sec figure -- not a huge savings (2.5%). It's pretty obvious this isn't going to work unless the NH payload were the size of a pea.

It'd pretty much have to have been, eh? Breaking a chunk off Pluto is a whole lot easier than breaking a chunk off Earth. A major impact with the relative velocity of the "selenogenic" Earth impact probably would've blown Pluto apart.

Such a large percentage of KBOs are binaries, what does that mean for the singletons that are left, since I assume most collisions would not form binaries, but create a bunch of smaller planetoids. IE, are there *any* "primitive" KBOs? What does "primitive" mean, anyway, if they all had to accrete by impacts?

space.com

Mission update.
It will take the probe 2 months to reach Jupiter!!!! Warp 4 or 5 I think....

On Star Trek: Enterprise, they went from Earth to Neptune in 6 seconds, so 2 whole months is kinda slow.

I think they should have called it DIET COKE
Device for Investigating Energetic Traces of Charged Objects Kneeding (sorry) Explanation

A sponsorship opportunity missed I think.

According to the link now, it will take 13 months after launch to reach Jupiter. This is in line with estimates earlier on this thread.

Bill

I don't know of another large KBO that is a binary (and by binary I mean has a moon that is a considerable percentage of its own size - I know lots of them have moons).
There are a lot of unknowns. And it has been suggested that tidal heating is a possiblity for Pluto/Charon as well.

Yes, but New Horizons will be travelling onwards for decades, and Star Trk: Enterprise never made it into the next season...

...I'll bet on the tortoise!

Hehe.

Yes, but New Horizons will be travelling onwards for decades, and Star Trek: Enterprise never made it into the next season...

...I'll bet on the tortoise!

Hehe.

I had been under the impression that tidal heating tends to dampen the eccentricity of a satellite's orbit, which implies that it can only last for a limited time before the orbit becomes nearly circular which removes the energy source. In Io's case (and Enceladus' too?) of course, this hasn't happened because the orbital resonances of those moons with other, larger moons force the orbital eccentricity.

So how could Pluto/Charon maintain tidal heating without a third large body in the system? Does this hypothesis assume that tidal heating only lasted for a short period after Charon's formation? Or are solar perturbations enough to keep Charon's orbit slightly elliptical?

As far as third bodies go, does the Sun count? That seems to be working for the Earth-Moon system.

Primary launch window for New Horizons is January 11 - February 14, 2006. If the spacecraft roars skyward within the first 18 days of that window, scooting by Jupiter for a gravity assist, it will reach Pluto in 2015.

"It’ll be the fastest spacecraft ever to Jupiter…13 months after launch," Stern said. "We pass the Moon in just nine hours."

Wow, just 9 hours to Moon How fast travel the spaceship 400,000 km/9 hours = 44,444 k/h = 12.34 km/sec. The previous astronaut must bear more than 3 days to reach moon.

The nuclear powered spaceship with 20 years of operation is really cheap against a widelly published a relatively cheap Phoenix Scout with $386 million for only no more than 5 months. The cost of New Horizons, including the launch vehicle and operations through the Pluto-Charon encounter, will be roughly $650 million.

More information article New Horizons Pluto Probe from space.com

If you want to send your name to Pluto!!! Visit and register at at New Horizons Web Server

Rodolfo

Pioneer 10 took eleven whole hours to pass Luna's orbit in 1972.

As I recall, the fastest an Apollo ever traversed the distance between Earth and Moon was about 56 hours -- and that was Apollo 8's homeward journey. (With no LM, they had more fuel remaining when it came to TEI, and they burned a little longer to get home a little sooner.) However, due to vagaries of trajectories, the Apollo 10 crew were the fastest, reaching a slightly higher velocity just prior to entry interface than any other Apollo crew ever managed.

-the other Doug

The astronaut had the disadvantage that it tried to orbit or even land on the moon.

As I am new with the space and am starting to understand about the space limitations.

Our actual problem is that with the present technology, the space must carry kilograms of combustion to space in order to break there (Hoffman Delta-V). It is understandable that it is very expensive to send extra kilograms to space for the breaking process. The solution must be that the space is able to generate braking force without having to carry the extra kilograms. Now, we have ion electric engine but it is not enough to break for a high speed of above than many kilometers/sec. Now I know at the present time there are many man working to overcome this.

Rodolfo