The speed of incomming asteroids?

[spacester]

Aw shucks . . . I’ve posted the formula for dV savings due to surface velocity many times here so it wasn’t that hard.<br /><br />I've spent years here as 'the math guy', all the time wishing for someone else to show up to help out. The elite types typically cannot be bothered to go deep enough into a subject to provide true understanding. We amateurs are genuinely excited about these topics and are not jaded in our thinking.<br /><br />I am not surprised one whit that someone else has shown up pointing out that ‘official sources’ on many of these questions are frequently wrong in certain details. Things like ‘escape velocity’ when they mean ‘orbital velocity’, confusing prograde with retrograde, stuff like that is amazingly common. <br /><br />My pet peeve is mission planning for Mars that completely fails to account for eccentric orbits. Some of the finest papers on going to Mars don’t even account for the 18-1/2 year cycle of delta V required. This is a fundamental physical constraint that needs to be incorporated in the mission design right from the start.<br /><br />I dunno if I’m going to be hanging out here much in the future, so perhaps as I accept your ‘brass filigree’ with one hand I should pass the ‘space math torch’ to you with the other. If these guys don’t get the picture pretty quick on this elitism thing I may just give up.<br /> <div class="Discussion_UserSignature"> </div>

 

[yevaud]

Apparently, so I did, at least with respect to short-period (e.g, less than 15 years) Comets. However, as to that distribution I'd mentioned:<br /><br /><i>The space orientation of the orbits of long-period comets appears random, <b>the number of such comets in prograde orbits being almost the same as the number in retrograde orbits.</b></i><br /><br />http://history.nasa.gov/SP-345/ch4.htm<br /><br /><i>Short-period comets do tend to have prograde orbits lying close near the ecliptic, but long-period comets exhibit all inclinations and all orientations, <b>both prograde and retrograde, roughly uniformly distributed in all directions from the Sun.</b></i><br /><br />http://astronomy.nju.edu.cn/astron/AT3/AT31402.HTM <br /><br /><i>This would also explain the fact that long-period comets move in all directions. <b>Roughly half of them move along their trajectories in the retrograde direction, opposite to the orbital motion of the planets.</b></i><br /><br />http://ase.tufts.edu/cosmos/view_chapter.asp?id=14&page=3<br /><br />And finally,<br /><br /><i>This must be reconciled with the <b>apparent equality of the number of prograde and retrograde new comets</b></i><br /><br />http://darwin.nap.edu/books/0309043336/html/260.html<br /><br />Ah well, my faulty recollection. Still, as to the retrograde versus prograde aspect of longer-term Comets, we are both equally correct.<br /><br />Interesting how a Comet can translate from Prograde to Retrograde, isn't it (Although the obverse is nearly impossible)? Galactic tidal forces as (one of) the principal mechanism(s). <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>

 

[yevaud]

Er, before you go accusing me of confusing prograde and retrograde (my using the wrong terminology from time to time notwithstanding, which, by the way, you have done as well - thanks for conveniently not mentioning that fact), see my above post. I didn't confuse the two. Thanks, "Math Guy." <br /><br />And frankly, I don't recollect you using any more math than any other user here. <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>

 

[spacester]

I made no accusations, sir. I was quite general in that statement. I refer to 'official sources' such as NASA and others. It's not as bad these days as when I started.<br /><br />Your recollections are quite incomplete, perhaps because you failed to participate in some of the more free-thinking M&L threads in the early years. Not all the math is in this forum. Trust me, I've posted a LOT of math and you do not credit yourself by challenging me on this. Of course, since the archives are lost for all time, my case cannot be made as well as I'd like.<br /><br />But shortly after the big forgetting, I reposted one of my first forays into the long math post.<br /><br />The Lunar Trebuchet Proposal<br /><br />I have some other stuff in my archives. All that effort and you don't even recollect it; elitism again, muchly?<br /><br />Oh BTW, Imaginova, you're welcome. My pleasure, don't mention it. <div class="Discussion_UserSignature"> </div>

 

[MeteorWayne]

Everything you said agreed with my post. Except....<br />1. A short period comet is defined as one with a period of 200 years or less. This is not my opinion, it is the rule implemented by Brian Marsden and friends.<br />I personally include one or two others with ~400 year periods, such as the parent object of the Lyrids meteor shower. That makes no difference in the statistics. <br />Long period comets are in a completely different range; 1000 to 100,000 year periods (or never for hyperbolic orbits).<br /><br />2. I never really made any statement regarding long period comets. They cone from the Oort cloud and are a small (if spectacular) piece of the pie. Despite that, I also have a possible explanation as far as the low likelyhood (or at least equal to the reverse so it balances out) of retrograde, long period comets becoming prograde. Because they are travelling against (retro) the path of the mass of the solar system, the gravity of any planet has less time to act. A prograde object has much longer periods to be acccellerated, hence it is more likely to have the orbit changed. Since accelleration's term is seconds per second (i. e. squared), that makes a big difference, much as Velocity Squared rules the energy of a meteoroid. <br /><br />MW <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[yevaud]

<i>perhaps because you failed to participate in some of the more free-thinking M&L threads in the early years.</i><br /><br />Ok, let's get this out of the way here and now.<br /><br />Spacester, <i>I predate you</i> here. I've taken two moderately long leaves of absence, and lost my entire post count twice (and so had to re-register twice). But I was here at the end of 99/very beginning of 2000. And if you don't believe me, ask Calli, Leo, Betel, Llovingo, Eddie, Pizzaguy, Orstio, SDCoyote, Stickhippie, Ricimer (Saiph), Peter, Fromazhi, whoever. Hell, you probably don't even <i>know</i> who some of them <i>are</i>.<br /><br />I still talk to Steph (PLC), Yales, Orstio. In fact, the first people to engage that nut-job Project Orion in scientific combat over his bizarre and dangerous ideas were Yales and I. Fact. That was over a year before you ever even appeared here, thanks. Shall I have Yales make an appearance and correct you on this?<br /><br />Further, go look in the Environment forum if you believe I do not post strict and well-informed scientific threads (Meteorology, Climatology, and Atmospheric Physics lessons I-IX).<br /><br />AND I might add, this was your comment: <i>I am not surprised one whit that someone else has shown up pointing out that ‘official sources’ on many of these questions are frequently wrong in certain details. Things like ‘escape velocity’ when they mean ‘orbital velocity’, <b>confusing prograde with retrograde</b>, stuff like that is amazingly common.</i><br /><br />You do not own this forum, this message board, and you darned certain <i>aren't</i> any paragon of scientific accuracy either. You are as fallible as <i>anyone</i> here. Anyone may misquote something in the heat of engagement. <i>Anyone at all</i>. And most have, <i>and freely admit it</i>. Saiph pointed out my error and I accepted it like a gentleman. <br /><br />AND, since you repeat the implication, apparently you did not actually <b>read the post I directed you to -</b> <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>

 

[yevaud]

Ok, fair, except that "200 years" is contrary to what NASA/JPL states; they state quite clearly that their guideline is 15 years or less as the short period Comets. Although they do also consider long-period as being 200 years or more.<br /><br />Of course, there are the (so far not mentioned) Intermediate period Comets, so we may be actually discussing the overlap between the two.<br /><br />(Pardon the diatribe at Spacester, but that has been in abeyance for some time now) <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>

 

[spacester]

Dude, chill out. I was talking about textbooks and authoritative websites. I wasn't talking about you at all. I see now that the choice of prograde/retrograde was a stupid one - I did not mean to refer to this thread but I guess I did in your mind.<br /><br />Yes you predate me here, I didn't claim otherwise. I mentioned the early days but I was trying to refer to the fact that most of my most math-intensive posts never attracted the interest of those who would go on to be authority figures here. I did a lot of math on M&L threads that you guys never posted on. After years of this, I notice a pattern. You stayed in the other forums for the most part.<br /><br />I've made errors and I've admitted them but I try very very hard to make none at all. My error rate is quite low, but I have gotten sloppy by my standards the last year or two. After all, I'm an amateur and the burden is on me to do my homework.<br /><br />I'm going to leave it at that and let you chill out a bit. <div class="Discussion_UserSignature"> </div>

 

[yevaud]

Then you chill out as well. We both can be blunt instruments at times. Let's not. <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>

 

[Boris_Badenov]

As a chef, a very amateur astronomer, & a SDC junkie, I think you guys are nothing short of wizards. But when you argue over finer points to the edge exhaustion, it makes you look petty. <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[yevaud]

Yes, this is exactly true. Look on all of this as clearing the air between us so we don't do so again. The preferable result. <br /><br />In fact, if you look at the dynamic here at SDC, some of us can be scientific brawlers in a sense. We wade in and take a stance, draw a line in the sand. Many of us learned to do this back when, when we had many, many members of the "woo-woo" crowd, frequent flamers, lot's of Trolls.<br /><br />Well, they're pretty much gone, but the attitudes remain. So over time, stress builds between people. Sometimes we need to let off the tension between us.<br /><br />Spacester is not a bad guy. There was just apparently an undercurrent of stress between us. I think that's over now. All well and good. <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>

 

[spacester]

Wow, what a well-worded post Yevaud!<br /><br />Agreed totally, back at ya. Please know that your gracious post hits home. Yeah, the woo-woo days formed a lot of habits, but also that’s when guys like you were at your finest. I had a different approach and loved setting them up for guys like you to move in for the kill. I remember the whack-a-nut ship and crew, PLC was great, too bad we lost her. BTW I remember every one of those old names except one; I lurked for um 3 months or so. In some ways it’s more complicated these days I guess; to me that’s due to the slow pace of actual space progress, a collective yearning for new glory days.<br /><br />I'm done venting and I've made the points I needed to make. I've put my point of view out there and you guys have been tolerant enough to let that happen, so I commend y'all for that and I'm already sick of this attack mode anyway. My points are now in the public domain and you guys have been exposed to them so I'll just let the thing ferment for a while. I finished my presentation on my six-word answer (To Ensure the Advancement of Civilization) today so I expect that thread to simmer down as well as we move into just dialog.<br /><br />Not that my iconoclastic streak is wholly satisfied. I'll still be rousing rabbles here and there. With apologies to Adlai, ‘Zealotry in the pursuit of Space Flight is no vice’ <img src="/images/icons/laugh.gif" /> <img src="/images/icons/wink.gif" /> <br /> <br />Oh I almost forgot, I do owe you guys an apology. Um, give me another week or so and by then I should be ready to do that correctly. (There’s a thread title I need to edit, among other things).<br /> <div class="Discussion_UserSignature"> </div>