Uranus

[robnissen]

<font color="yellow">New Horizons' visit is going to be heartbreakingly brief.</font><br /><br />Well put. Hopefully New Horizons won't be like that first Mars probe that just happened to view the only part of Mars that had a strong resemblence to Earth's Moon. I doubt that will happen with New Horizons, because I assume, although I don't know, that it will get closeups of much, if not all of one side of Pluto. Hopefully, that side of Pluto doesn't look like Earth's moon. <img src="/images/icons/smile.gif" /> Of course, if it did, that would be quite a news flash. <img src="/images/icons/smile.gif" />

 

[jaxtraw]

<blockquote><font class="small">In reply to:</font><hr /><p>To me Sedna is probably a dwarf...<br /><br />...As far as origin is concerned I do not know. Given the relatively low perihelion for an OOC-object, I would bet on solar origin, with formation in this region. <br />But the other three options are open: <br />1) formed far closer to ice limit, then ejected to the outskirts (but requires two big delta-Vs, one for aphelion, one for perihelion (*)) <br />2) extrasolar, pre-existing the Sun, caught in the Solar primordial nebula, and surviving its spiraling <br />3) extrasolar, captured by Solar System along Sun's galactical path<p><hr /></p></p></blockquote><br /><br />--or it's a former moon of a planet that once orbited at around 80AU which, er, isn't there any more...<br /><br /><img src="/images/icons/wink.gif" />

 

[alokmohan]

Probes are costly.Lets visit mars and terraform so that we can have our future home.

 

[h2ouniverse]

In reply to:<br />--------------------------------------------------------------------------------<br />or it's a former moon of a planet that once orbited at around 80AU which, er, isn't there any more... <br /><br />--------------------------------------------------------------------------------<br /><br /><br />Yes why not.<br />Actually to me that was included in the "solar origin, with formation in this region" assumption.<br />I hope the new dwarves Mike Brown should soon announce will include multiple systems.<br />For they are generally more prone to have some active bodies. (hence liquid water at some depth, again).<br /><br />Watery regards.

 

[ihwip]

While we would need to have a very speedy probe heading to Uranus I think utilizing the gravity of Saturn to slow down might help cut down on the travel time. Another idea would be to jettison a probe early with force to slow down the orbitter. Does anybody have an estimate of a best case scenario?

 

[jaxtraw]

<blockquote><font class="small">In reply to:</font><hr /><p>One expansion on my previous post. When Voyager spied Jupiter's ring system, it wasn't that big of a surprise in that due to Uranus' unique tilt we already knew we had two confirmed ring systems already among the giants. That's kind of what I meant by that paradigm altering occultation that occurred not long before Voyager itself came to be.<p><hr /></p></p></blockquote><br /><br />Some years ago I read a book about the discovery of the Uranian ring system written by its discoverers. When they wanted to have Voyager look for a Jovian ring or rings, they encountered enormous scepticism from NASA scientists who thought the chances of a Jovian ring to be tiny.<br /><br />The paradigm shifts, and people downplay how resistant they were to said shift afterwards. It's a bit like, if the Global Warming/CO2 hypothesis were to be disproved, a few years later you'd find lots of climatologists saying, "well you know, I was never entirely convinced..." kind of thing.<br /><br />Anyway, the impression I got from that book was that the ring discoverers were considered by much of the astronomical community to be rather loony to be even proposing a Jovian ring.

 

[jaxtraw]

I think the problem with a Saturn gravity un-assist would be that (a) that leaves a long cruise time at lower speed (between Saturn and Uranus) and also you could only do it once per Saturn orbit (plus a bit because Uranus is moving too) when they're in the correct orbital positions. With a year of 29 years, that's not many launch windows.<br /><br />Throwing away mass is just an inefficient rocket <img src="/images/icons/wink.gif" />

 

[3488]

Hi anvel.<br /><br />If a Uranus orbiter was approaching now, it would not be too difficult, because<br />the Uranus system will be prested edge on, in other words the spacecraft would<br />already be in the plane of the system.<br /><br />Had lets say Voyager 2 entered orbit around Uranus (imaginary exercise) back in January 1986, <br />Voyager 2 would have entered a polar orbit around <br />the gas / ice giant planet, <br />as the Uranian system was presented to Voyager 2 as a 'Dart Board'.<br /><br />Now that would be more difficult to bring into the plane of the major moons, as Voyager 2's<br />orbit would have to be bought down from a polar orbit into an equatorial one.<br /><br />Now & in 2049, the Uranus system to an approaching craft would be presented equatorialy.<br /><br />Neptune is a difficult one. The way around it would be for a Neptune orbiter to brake into orbit <br />over Neptune's morning hemisphere as that would enable a retrograde orbit, <br />matching Triton's (Galileo & Cassini broke into orbit around Juiter & Saturn respectively <br />over their afternoon hemispheres, to enable prograde orbits).<br /><br />With Neptune, true this would solve the problem with Triton, but Proteus, etc would be <br />travelling very fast indeed in the opposite direction, not to mention Neptune's own rotation<br />would be in the opposite direction.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[nexium]

Am I to understand that a head on close approach to Triton would decelerate a probe, while approaching from the rear accellerates the probe = gravity assist manuver? Neil

 

[vogon13]

A beginning polar orbit about Uranus (and eventually gravitationally adjusted to equatorial) would be very interesting for the magnetosphere and fields and particles folks (they always feel short changed anyhow). And it would still provide interesting viewing aspects of the moons as the craft penetrated the equatorial plane as it's orbit was cranked down.<br /><br />Statistically, for most random feasible launch dates we are going to approach Uranus at an average 45 degree angle to the equator, might as well look at it as an opprotunity.<br /><br /><br /><img src="/images/icons/laugh.gif" /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[h2ouniverse]

Hi Anvel,<br /><br />Aerobraking would be great. Unfortunately NASA (and a fortiori ESA!) looks quite shy at tempting that. They consider suicide entries into atmosphere (done on Jupiter, envisaged for Saturn), but not capture at short term. Apparently the issue is the predictability of the atmosphere thickness and pressure profile at the time of the aerocapture. <br />Underestimate upper atmosphere altitude, and you burn the probe. Overestimate it, and the probe will continue escaping Uranus gravity well.<br /><br />But to know that, you need more studies and measurements of the atmosphere...a vicious circle!<br /><br />Do you know whether they are progressing in building robust capture scenarii?<br /><br />Regards.<br />

 

[robastor]

anvel<br />solar system<br />08/14/07 03:56 PM<br /> <br />Re: Uranus [re: 3488][link to this post] <br />Reply to this postReply <br /><br />One of the things overlooked about Uranus is how it changed the paradigm about planetary ring systems. By being tipped over on its side, an occultation by a star easily revealed its ring system. Ponder for a moment if Uranus had not been like this, but had a rotational axis similar to the other gas giants. It is likely that those rings would have escaped detection until the arrival of Voyager.<br /><br />Recall how when Voyager finally arrived at Uranus much of the world including planetary scientists erupted in a great big ho-hum. Had this ring system remained a mystery until Voyager, the Uranus encounter would not have been so apparently anticlimactic.<br /><br />--<br /><br />Actually, the anticlimax was because of another over shadowing event. Voyager 2's closet approch to Uranus was offset by two days (if I remember giht) of the Challenger explosion. All attention shifted away from Uranus for that reason. I remember feeling very let down that there was hardly any coverage until a few months after the fact. Astronomy magazine had the first true in-depth encounter report that I remember seeing, approximately three or four months later.<br /><br />Rob

 

[h2ouniverse]

I have already suggested to use Titan to aerocapture around Saturn but was answered by JPL analysts that the mission analysis would be too sensitive (this time to Titan's position vs the probe trajectory). <br />I am afraid they are right.<br /><br />There is no aerocapture by Saturn considered now, just entry probes for study of the top 20 kilometers.<br /><br />I think we need an entry/rebound strategy and probe design that would result into a negative feedback loop, self-adjusting trajectory. But no specific idea about how to achieve it.<br /><br />Regards.

 

[Kalstang]

I would like to thank you all for participateing in this thread. It is very interesting to read and I have enjoyed it immensely. Thank You. <div class="Discussion_UserSignature"> <font color="#ffff00"><p><font color="#3366ff">I have an answer for everything...you may not like the answer or it may not satisfy your curiosity..but it will still be an answer.</font> <br /><font color="#ff0000">"Imagination is more important then Knowledge" ~Albert Einstien~</font> <br /><font color="#cc99ff">Guns dont kill people. People kill people</font>.</p></font><p><font color="#ff6600">Solar System</font></p> </div>

 

[3488]

I think you issue is risk.<br /><br />I agree, I think aerobraking is certainly a way forward to reduce journey.<br /><br />I agree, the MESSENGER mission to Mercury is taking far too long to reach such a close<br />target.<br /><br />NASA I think is afraid of failure. I can see that. There is no way that I would want <br />to see the mission fail however.<br /><br />The advantage of a ciruitious route is the possibilty of extra science. Remember the <br />Galileo encounters of asteroids 951 Gaspra & 243 Ida?<br /><br />They alone were worth the extended journey time to Jupiter. I know, on the original route<br />an encounter with the very large asteroid 29 Amphitrite<br />was on the cards!!!!<br /><br />But also on the other foot, is the possibilty that extended journey times increases <br />the risk of damage, increases the risk of impacts from natural objects, solar activity, etc.<br /><br />Is a follow up mission to Saturn after Cassini officially on the cards????<br /><br />I hope so!!!!<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[jaxtraw]

Doesn't Mercury have a similar "slowing down" problem? It's easy to get there, more difficult to get into orbit because of the velocity picked up on a (Hohmann??) "transfer orbit falling into the sun".<br /><br />So the circuitous route is a means to need less slowdown on arrival, or something, if memory serves. It's all really down to our power-compromised chemical rockery again... leastways I think that's why MESSENGER's spending half a lifetime getting there.<br /><br />I really think entirely personally that we ought to drop ISS and the manned programme for a little while and concentrate on (a) robots and (b) propulsion systems. But I say that as a Brit, so by "we" I mean "everybody else" since "our" space budget is about 50p. So hats of to the Americans, Russians, Japanese, and the rest of Europe for doing what you're doing.<br /><br />I read just now that the Peoples' Republic Of Ukay is spending £170bn on quangos- bureaucratic agencies like the British Seaweed Marketing Board and the Park Bench Regulation Agency and so on. Make me prime minister and I'll scrap them all, give half back as a tax cut and spend the other half (a) funding a nuclear rocket programme and (b) getting an orbiter to Pluto to greet New Horizons when it gets there <img src="/images/icons/smile.gif" />

 

[brellis]

<font color="yellow">It's all really down to our power-compromised chemical rockery again...</font><br /><br />Risk versus reward: let gravity do its thing over a longer period of time, and there aren't a bunch of nukes floating around the solar system.<br /><br />On the other hand, we know we can build, launch and insert them into their orbits safely, so why not put nukes on all of them?<br /><br />Another tack: ion propulsion. Send multitudes of probes out with ion engines, and 20-50 years from now, they've arrived at their targets, for relatively little $$. No danger of getting nuked in the future. <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[3488]

Yes Mercury does have that huge problem, enormous speed during Hohmann transfer<br />& Mercury's small mass (about 5.6% that of Earth).<br /><br />Yes the circuitous route does enable a considerably slower approach speed.<br /><br />However, it still seems a very long time to reach this nearby planet.<br /><br />You are British too? Yes iagree about these stupid quangos. Scrap the blooming lot.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[jaxtraw]

I think an interesting perspective on govt. spending is presented by the quangos. We're a small nation who supposedly can't afford a meaningful space programme and yet-<br /><br />Spending on quangos in 1997 (when TB came to power) was around £24bn. Now it's £170bn. That's £146bn per year expenditure we weren't spending before.<br /><br />Cost of NASA (2007): $16.8bn, less than £10bn. If we just cut the quango budget by £10bn- less than 6%- we could spend as much on a space programme as the mighty USA!<br /><br />So maybe we shouldn't spend that much. But with a much more modest budget we could still, for instance, do some incredibly good science with probes to, say, the asteroids. I'd be over the moon if the first 1 Ceres lander was sporting a Union Jack <img src="/images/icons/smile.gif" /> <img src="/images/icons/smile.gif" /> Or why not fund another pair of MERs? (Less than a billion, surely). And so on...

 

[h2ouniverse]

Hi jaxtraw,<br />1) Mercury is pretty difficult to reach as well indeed (more than 30 km/s delta-v difference, and that's just for Sun's gravity well).<br />2) And yet NASA (Messenger) and ESA+JAXA (BepiColombo) are spending billions for that, instead of the Outer system (sigh!)<br />3) I would be proud of an European or ESA flag floating on 1 Ceres (provided that it is COSPAR-compliant, properly sterilized, LOL). UK contribution and geo return in space programmes are one-sixth of ESA Science budget. Brits are entitled to feel the 12-starred blue banner represent them as much as other taxpaying peoples of this continent.<br />4) ESA's science budget is anyway so low when compared with NASA's<br />5) Sorry to ask, what the hell is a quango??? <br /><br />

 

[Swampcat]

<font color="yellow">"Sorry to ask, what the hell is a quango???"</font><br /><br />QUAsi-Non-Governmental Organization.<br /><br />Google is your friend <img src="/images/icons/wink.gif" />.<br /><br /> <div class="Discussion_UserSignature"> <font size="3" color="#ff9900"><p><font size="1" color="#993300"><strong><em>------------------------------------------------------------------- </em></strong></font></p><p><font size="1" color="#993300"><strong><em>"I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."</em></strong></font></p><p><font size="1" color="#993300"><strong>Thomas Jefferson</strong></font></p></font> </div>

 

[brellis]

<img src="/images/icons/laugh.gif" /><br /><br />I thought it was the currency of some obscure nation. <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[yevaud]

If I ever found an obscure nation, that's what I'll name it. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[jaxtraw]

I found an obscure nation, and I did!<br /><br /><img src="/images/icons/laugh.gif" />

 

[jaxtraw]

I think it's QUasi Autonomous Non-Governmental Organisation...<br /><br />It's how UK.gov increases the sprawling bureaucracy. If they want to regualate cheese, for instance, in the old days you'd have Her Majesty's Department Of Cheese. But nowadays in order to pretend it's not a government bureaucratic department they make it pretend-independent and call it The Cheese Agency of the Office Of Cheese (OFFCheese for short). The major advantage to government is that it's outside the civil service and government, so whereas the Cheese Minister would be responsible for the failings of a HM Dept. Of Cheese, nobody's responsible for OFFCheese and it can just sit there consuming money and telling people what to do and nobody can do anything about it. If they ban Wensleydale for instance, you can moan, but you can't actually bring them to account to explain why.<br /><br />Anyway, I appreciate this is all too political. What I was saying really was if we have to give billions of groats to agencies, I'd rather a few of them go to a proper space agency instead of some bunch of waster regulating cheese. Maybe then we could get a proper assault on the Ice Worlds going and get loads of science done. I'd like that.