Pesky Dust Bunnies Impose Lethal Terminal Velocity(Vt) Factors

(Mars offers damn little deceleration drag, and our moon offers absolutely zilch worth of Vt)

By; Brad Guth / GASA~IEIS     updated: August 07, 2005

Besides whatever usual substances are physically influxing upon the likes of Mars, our absolutely naked moon and upon Earth itself, and of folks having to survive a given lunar EVA in spite of all the flak, this page is somewhat about the notions of skydiving, such as upon Mars, our moon or upon Venus which should to be a real hoot, that is if you don't get absolutely bored to death before touching down at 0.62 m/s, as being their nighttime density that's nearly 10% of water, as such I'm not all that certain that you'll even be needing a parachute for that one.

Very interesting report with a somewhat extensive composition upon dust influx;

Seems there's been an old figure published by Hans Pettersson in 1960, of there being an accumulation of 14.3e6 tonnes per year as the meteoritic dust influx rate (that's surviving reentry) as arriving upon the surface and into the vast oceans of Earth. Of course, much of that dust influx may never have reached the surface, instead converted into thermal energy and becoming more or less of another gas element, or gas composition as absorbed into our atmospheric matrix, and obviously some if not a great deal of space debris must have been deflected, which obviously depends entirely upon the incoming trajectory plus mass/density and even somewhat of composition and a touch shape having some influence if it's ever to survive a glancing blow, much less survive reentry as to reach the surface. Whereas the moon offers absolutely no such atmosphere to diminish nor to as to deflect squat, thus obviously everything headed directly towards and/or merely lingering within the path of the moon impacts with truly horrific energy, whereas nearly everything other that's merely headed towards the vicinity of, and/or sufficiently cruising near the moon's gravity (say up to 2r), will most likely become influenced by the lunar gravity into impacting upon the moon.

Though an actual household "dust-bunny" is more likely at most well under .1 mg/mm3 (100 kg/m3) rather than of the robust 2 mg of which I've given favor as to those sorts of lunar impacting dust-bunnies of outer space, having their somewhat more substantial nature of perhaps an iron like composition, and otherwise I've only been mindset upon using the notion of 2 mg as for keeping the math as simple as possible, especially since the kinetic formula (KE=.5MV2) essentially divides whatever mass by half, thus half of 2 mg worth of mass = 1e-3 g, which seemed like the right sort of averaging thing to apply, though in reality a micro-meteorite sort of "dust bunny" might actually be anything from 1 mg if not as much as 21.5 mg per particle, entirely dependent upon whatever the heck it's composed of (water 1.0, silica 2.2, basalt 3, iron 7.8, silver 10.5, or platinum 21.5).

Keeping in mind that, of a 2 mg dust-bunny as situated on the moon is going to become worth 1/6th that amount, whereas this sort of 0.333 mg lunar item is going to react very much like that of a household dust-bunny, especially whenever there's a exhaust thrust associated with a lunar lander taking up a rather considerable down-range approach, or that of whatever is impacting is surely going to kick a rather substantial amount of existing lose material and impact shards for great distances.

Also keeping in mind, that I've been asking of others about the terminal velocity of space itself, as obviously there are limits imposed upon physical items having to travel though this supposed vacuum of space, yet lo and behold, I've been kindly informed that there's absolutely nothing slowing anything down, except gravity. Which transposes into absolutely nothing keeping anything from speeding up as headed towards an influence of gravity. Even though I do not accept the absolute unlimited Vt of space as being the truth and nothing but the truth, in which case that only further reinforces upon the absolutely nasty and downright lethal dust-bunny factor upon folks having to survive while working upon the moon.

MOON DUST (as in those 2+mg dust-bunny category) = LETHAL INFLUX FOR FOLKS WORKING THE MOON:
Hartmann had suggested upon a figure of merely 4,000 tons per year, as obtained from his own published work, although this estimate was calculated from a terrestrial influx rate as merely taking into account the smaller surface area of the moon. Of the Apollo samples supposedly extrapolated a wee bit further conservative upon that figure, of their reported accumulations having to suggest 15 tonnes/year (there's absolutely nothing independently on hand to even support that low estimate). Another average meteoritic influx rate of roughly 4e-9 per square cm per year seems to have been more recently established upon an influx rate of approximately 21,000 tons per year. Whereas all of these are mere estimates or guestimates having to be based upon some notion that the moon was always exactly where it is, and thus nearly as old as Earth (perhaps -1 billion years).

If we took that more recent estimate of 21,000 tonne/year as a basis, that's 21e9 grams, and that becomes 21e12 mg, whereas the 40e12 of all the ups and downs of what the lunar surface has to offer represents that better than 0.5 mg/m2 arrives per year. Thus within any given 20 m X 20 m patch of lunar terrain, there's that average 0.5 mg dust-bunny touching down every day.

Of course this tonnage worth of essentially lunar dust-bunnies isn't necessarily exclusive to any such 2 mg class of particles, as more than likely those sorts of accumulations could actually be below 1 mg, but still not inclusive of the overall influx of most other micro-meteorites, plus others that should average as better than 3.5 g/ccm, and not to exclude actual meteorites of any greater size/bulk, as well as much greater density/ccm, of which the surface of Earth receives the remains of perhaps one such delivery per km2/year. Especially as to the degree and extent that has been clearly identified of what's previously been existing on Mars, which by the way offers somewhat of an thin atmospheric buffer zone that'll vaporise and/or deflect any number (possibly deflecting <10%) of such incoming debris to a fairly good extent, of which there's been absolutely nothing as such defending our moon for all of these billions of years.

Obviously of what's within the path or specifically targeting upon the moon is going to eventually impact, as there's absolutely no atmosphere to deflect nor diminish anything, whereas upon average this initial encounter of good velocity should be considered as a minimum of 15 km/s, even though the gravity influence of 1.623 m/s should skew that estimate to a somewhat greater velocity of at least 20 km/s. Being that any item just drifting through could also become a 40+km/s event, and of whatever is mutually advancing head-on towards one another makes that encounter into the 66+km/s event, whereas the likes of a well known 72+km/s meteor + the 30+km lunar SOA = 105+km/s, and that's got to hurt.

However, I do believe the formulas stipulate that from just a 25 second free fall should impose at least another 1.642 km/s on top of whatever the initial velocity, whereas 50 seconds worth offers 13.36 km/s, and so on. And since there's no atmosphere, the 250,000 m3 volume of the entire Hindenburg will just as likely impact at the same moment as would the 1 cmm dust-bunny. Fortunately there are relatively few of those 240 tonne Hindenburgs headed for the moon, though obviously there are potentially billions if not trillions of potentially lethal dust bunnies per day, where any one of which might just as soon nail your hide as not. All that you'll have to do in order to survive is not to be standing upon any one of those 40e12 m2 of lunar soil that might be on the receiving end of one of those daily dust-bunny impacts, although one such impact per 100 m2 could certainly ruin the day as for being anywhere within that (10 m X 10 m) impact zone, thus the odds of encountering one such dust-bunny per m2 upon at least once every 100 days is still suggesting rather damn poor odds, if not an absolutely piss poor situation if you're situated anywhere within that impact shard range, or potentially lethal 10 m2 death zone.

In other words of wisdom; THE MOON IS NOT A WALK IN THE PARK.

At 2r the initial influence becomes but 1/4 (g=0.40575 m/s), and at 4r we're down to an influence of 1/16th (g=0.101 m/s) of what the 1r surface gravity constant of g=1.623 represents, thus of whatever is of a glancing blow that's much over 3r (3,476 km), and especially those of 4r being 5,214 km away from the lunar surface isn't nearrly as likely to being sucked in. Though once again, even this aspect becomes somewhat dependent upon the particle trajectory and of it's mass and speed in relationship to that of the moon, such as for mission orbiting needs to sustain their speed, or else. A particle of mass of any size or volume having sufficient mass and applied velocity, thus kinetic energy of it's own (such as that of an intentionally orbiting satellite), such a particle, meteorite or whatever can just keep on trucking pass the moon, with only it's path somewhat altered by the lunar gravity influence. Although, if such a dust-bunny were to be averaging along at such a 4r near miss of 15 km/s relative the the lunar motion, within the time of just passing by the moon's diameter is 231 seconds worth. However, upon the expanded 4r radious, of a glancing/non-orbiting event, thus nearly a straight pass-by trajectory becomes roughly 1000 seconds, 16+ minutes worth, which is a relatively long duration of being within lunar gravity exposure, even if that's only 0.101 m/s/s. A full half circumnavigation about the moon at r4, while sustaining 15 km/s is 24+ minutes worth, somewhat insuring a most likely return of that item until there's nowhere other to go, except into the lunar surface or Earth because, what other influence is there to keep that eventual impact from happening?

Thus the clearing/collection zone of the lunar path is most likely within the 4r grip of gravity influence, a pathway or collection zone of 13,904 km, whereas beyond that range you shouldn't need all that much speed and/or thruster energy in order to avoid being sucked in. However, a sperical/donut collection zone of nearly 14e3 km worth is actually quite a good deal to respect, especially since the moon itself offers absolutely no other influx protection whatsoever. In other words, the moon physically collects and collects, if not on the first pass then eventually in the future is where all that is headed for and thereby enters the collection zone shall arrive upon either the moon or that it attempts to enter the environment of Earth, that is unless something greater than the moon comes into this gravity tug-a-war zone. The last time I checked, there was nothing other.

A somewhat more current estimate upon the meteoritic dust influx rate that's actually been reaching the surface of Earth has been suggested that this rate could be as much as 100,000 tons per year, although we also have ourselves yet another 5e6 ton/year estimate which apparently squares nicely with the nickel content of deep-ocean sediments. Of course we must take into account that up to 90% of whatever tonnage that's incoming never makes it to the surface, as for being deflected and/or vaporised by our relatively thick atmosphere, as compared to that thin atmosphere of Mars which most likely can't deflect 10%.

"One is tempted to ask why it is that Pettersson's 5-14 million tons per year figure is slammed as being 'tentative', 'very speculative' and 'completely wrong', when one of the same critics openly admits the results from the different, more modern methods vary from 100 to 1 billion tons per year, and that even results from identical methods differ?
Furthermore, it should be noted that Phillips wrote this in 1978, some two decades and many moon landings after Pettersson's work!"
  And, I'll have to agree, as to how can folks of such supposed expertise and of having all of that NASA/Apollo feedback be so entirely wild about their amounts if deposited tonnage per year, as you'd think every researcher would have become setteled upon a specific amount that at worse case should not vary by more than +/-5%. Obviously there is still a major disagreement that's at risk of exposing a great deal more than meets the eye.

It's rather clear, as far as supporting Earth science, and that of being primarily influenced by our moon, that our need for having an array of small and thereby relatively efficient and minimal cost, as well as well dispersed probes (javelin or otherwise) reporting back to Earth upon the intensity of the physical lunar environment, and thereby of the ongoing severity of impacts, as can most accurately be determined from such miniature seismic and even by way of sufficiently sensitive acoustical measurements that can extract such data from the micro-thin sodium like atmosphere, as these deployments certainly would have accomplished the task of obtaining such invaluable data, as in real moon and thereby real time feedback as of decades ago. Interactive Earth/moon laser communications should also have been established, so that as an actual robotic laser cannon deployment would have become the standard by which significant interplanetary communication would have been taking place as of at least a decade ago. I'm not absolutely certain, but I do believe all of this could have been managed at least two decades ago, if not before, and at most not 10% the cost of our doing Mars, and of just the lunar VLA/SAR imaging performance alone would have easily superseded Hubble for the likes of everything that's humanely accessible, and even as far out as Sirius/abc is barely within the lunar VLA/SAR imaging capabilities, and then some.

In other words, the moon as for being as hot/cold and downright otherwise nasty towards mere humans as it is, at least it offers us a virtual real time sterilized morgue of accumulated dust, plus loads of micro-meteorites and of course tens of thousands of sizable meteorites and of their shards, as to a far greater extent and of obviously being hundreds of times closer than of any obtained from the likes of a sub-frozen and irradiated to death Mars surface. Plus, there'd have to be loads of subsequent lunar basalt shards from such entirely uninhibited as well as non contaminated impacts, by which a great deal of truth about the lunar geology as well as for the environment of space and of the honest to God risks of space travel could have been well established (no more spendy and potentially lethal guessing games), as of decades ago. Instead, we've got absolutely zilch, as in squat nothing worth of any database to utilize, and only NASA's moderated hype and infomercials made to look and sound like real science, and/or loads of their skewed (politically corrected) suggestions as to what's out there, and of their subsequently focusing our limited funding and talents upon what's of importance for our next adventure that can't benefit humanity even if it tried.

Clearly those terrific images of past and current Mars probes have stipulated as "proof positive" as to the extensive influx of your typical meteorite, micro-meteorites and dust making their way onto the Mars surface, and to always consider that Mars actually has a slight atmospheric buffer zone, whereas our moon essentially offers nothing whatsoever. Yet oddly the Apollo documentation not only managed to allude nearly all the radiation factors of what was fully solar plus cosmic influxing, as well as for enduring the horrific secondary issues of their being entirely surrounded by a fairly massive resource hard X-Ray class TBI dosage, but then somehow never could manage to photograph a single landscape that reflected at 11%, much less of the much darker basalt that should have been just about everywhere, nor were any of their photographs the least bit spectrum skewed, or capturing terrain as accommodating 1% of the meteorite debris and shards as depicted strewn about Mars. Not in all of their supposed EVA timelines, cameras with ordinary Kodak film taking those perfectly unskewed pictures nearly continuously, was there ever an impact of any sort noticed, even though a dust-bunny clocking in at merely 9.48 km/s should have been rather impressive to say the least, as that's merely accounting for 60 seconds worth of free fall yields 2921 meters, and that's for not even including whatever initial velocity, whereas that of a 2 mg dust-bunny is going to yield a rather nasty 22.477 MJ event. If you'd care being a little more honest, try out a little greater mass, as well as for adding whatever the likely initial velocity factor into that dust-bunny and/or speck of whatever influx and, lo and behold, you've got yourself serious "Trouble in River City", or in any other town on the moon.

As for another calculation upon the lunar "Dust-Bunny" impact factor:   I'm fairly certain that you should be capable of offering an all inclusive calculation, thus complex and therby impressive do-everything formula that'll easily supersede these three primitive individual formulas that I've utilized. And BTW; you should accomplish this for a free fall as based upon the likes of 120 seconds and so forth, out to a distance of at least 1728 km, then try this out on an actual spec of sand at 20 mg, or a somewhat larger particle of 200 mg and so forth, such as for whatever a 2 kg nasty rock has to offer, especially if that rock were comprised of mostly iron and a little platinum composite fore creating an item of 10 g/ccm, of which I do believe such can certainly ruin your entire EVA, even though a 3~4 g/ccm worth of mostly basalt is bad enough, or even that of a dust-bunny (due to it's itsy bitsy size), as such could quite easily penetrate most any moon suit.

distance traveled (d=.5g*t2)
Time (t) = square root of (d/.5g)
Final Velocity (Vf=Vi+g*d)
Kinetic Energy (KE=.5M*V2)

Of course, as the further out you are, the more the duration that's available for the fall from heaven (as per distance traveled before final impact yields the greater Vf) is where I believe the formula needs to become modified as for depicting the average of gravity influence, as obviously at the range of 1738 km away from the lunar surface is where the gravity constant starts in at 0.40575, as opposed to being on the surface at 1.623 m/s/s. Thus I'm using a rather simplistic g=1 m/s/s as influencing a free-fall from 1738 km, that which should transpire within 1463 sec (24.4 minutes), obtaining that final velocity of 1738e3 m/s as based upon using the average g=1, delivering a worth of 3e12 Joules per couple of grams, whereas that nasty 2 kg item will be stricking home plate at 3e15 Juoles.

Unless I've managed to skew those numbers, it seems that 1738 km/s upon final impact is certainly way more impressive than any 72 km/s worth of some meteor, and still way more than the combination of 72+km and 30+km giving 102+ km/s, by a factor of 17:1. Thus is why I've been looking for the Vt of space travel, so that I might apply that as needed in order to establish the real honest to God lunar environment.

SKYDIVING Mars and especially our moon has got to hurt

From the research of what others accomplished, I understand that the terminal velocity of a 100 kg (220 lb) skydiver upon Mars is roughly capable of obtaining 725 mph (324 m/s), as opposed to a maximum of 125 mph (56 m/s) free fall with perhaps a 0.1 m/s soft landing on Earth, or perhaps that of a 10 m/s semi-soft landing upon Mars having a parachute that's roughly ten fold larger. On the other hand, of the Venus skydiving terminal velocity when taking into account the mostly CO2 instead of O2/N2 of Earth = 1.5:1, the 65+kg/m3 as opposed to the 1.2 kg/m3 of Earth = 54:1, and the 90.5% gravity makes for the near surface Vt of Venus as being roughly 0.62 m/s.

Unfortunately, as for any notion of folks skydiving on the moon, whereas that pathetic (considerably far less than Mars) lunar atmosphere isn't helping one bit. Even though the gravity is roughly half that of Mars, your terminal velocity factor is simply a real fear-factor absolute killer, whereas the following jump by that 100 kg fearless soul is offered as just an example;

15 seconds of free fall offers 182.6 meters.
This also creates your Vf of 296 m/s (achieving nearly 5.3 fold Vt of skydiving upon Earth)
Then a somewhat nasty 4.38e9 Joule impact (thats 4.38 GJ, as in creating your very own personal crater).

Not only is this seriously bad news for any lunar skydiver, but also of accommodating those micro-meteorites and even common dust bunnies that come from afar, that soon become the real pesky sorts of dust-bunnies from hell that'll need to be avoided at absolutely all cost. Unfortunately, I have no freaking ideas as to how a mostly synthetic moon suit could survive such an environment, at least not unscaved, or perhaps perforated is more likely.

In other words; for something to reach the final impact velocity of 30 km/s, that item (regardless of shape, volume or mass) need only require at most 19 km, and that's barely 1.1% of 1r (1738 km), thus the factor of g=1.6 m/s/s applies.

I realize that from time to time I've managed somehow to nearly always get my formulas mixed up, in part by way of my having too much on what's left of my mind, plus by way of my not having one of those do-everything sorts of math software packages, like all of my critics rely upon, thus my long-hand and all too often short-handed methods mixed in with what some of my three remaining dyslexic brain cells having been somewhat creative, whereas I've either managed an unintentionally overshot or undershot the mark, but none the less proven my point to the sorts of honest folks that are actually a bit smarter than they claim, which of course can't be said for the bulk of NASA's "spin" and "damage control" moles and borgs, as they always seem to claim they "knowing nothing" unless it's been officially posted within their NASA/Apollo bible of all there is to know about space travel, not to mention our moon, and it seems even of that much is only to be shared on a need-to-know basis, or exploratory discovery game of playing their cold-war hide-and-seek.

The consideration as for the Venus terminal velocity may need to be checked out, as I'm fairly certain I've over/under shot the mark there as well, but again you should by now get the notion of what's what, as even if my math becomes a little skewed, the Venus atmospheric density of 65+kg/m3 as opposed to our 1.2 kg/m3 offers the first factor of 54:1, plus the fact that the Venus atomsphere is mostly of CO2 is good for another 1.5:1 that starts getting interesting at 150+km as opposed to our 50 km, offering another 3 fold opporyunity of decelleration zone depth that's in addition to whatever the final density and of 90.5% gravity to boot (not to mention another 5+% density increase as for their season of nighttime) is going to deliver that 0.62 or less m/s factor of Vt.

Calling Venus is about making reservations (if we're not being allowed to officially look at Venus, much less even discuss the possibilities, then it certainly can't hurt focusing a few laser cannons upon it);

If you're perchance the sort of individual that's more interested in the truly viable prospects of our achieving interplanetary communications (contacting ETs without utilizing radio), as for that relatively simple and extremely efficient quest, I've added lots of notions, if not a little too much quantum packet information into this following page;

Here's the latest deliveries upon what other is new and improved, and of what's certainly hot, as offering a bit more than you may need to know of what my three brain cells can deliver on behalf of Sirius lizard folk terraforming the likes of Mars, Earth and Venus.
Cost or Consequences is merely offering yet another vantage point or skewed perspective.
Of lizard folk from Sirius/c terraforming the likes of Earth might be asking a bit much.
Cometh the ice ages, right on a Sirius schedule, every 110,000 years, at least until mankind came along.
The likes of carbon life on Sirius/c, Venus and even Mars should have their fair share of diatoms.

To the INDEX page: GUTH Venus (with loads of recently posted UPDATES)
alternate URL's:  and
Copyright © 2000~2004 - Brad E. Guth
GUTH Venus: All Rights Reserved
Webmaster: Brad Guth - Brad Guth / IEIS~GASA   ~  1-253-8576061
created: March 11, 2004

Brad Guth / IEIS
(due to officially DHS sanctioned email account bashings, as well as unauthorized moderation of my email, if push should come down to shove, you can post your reply in Google using "bradguth-email" or simply include "guthvenus" within your subject line, in that way I'll find you, though even GOOGLE can be moderated/excluded by you know who)