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As someone else pointed out, most of the re-entered objects that are reasonably intact are spherical tanks. They're one of the few components of a spacecraft that are very solidly built. Most are titanium, or titanium wrapped in Kevlar, so they can take re-entry temperatures. Spheres have good re-entry aerodynamics. Nose cones have been hemispherical since the late 1950, after it was discovered that pointy noses look cool but don't work well. (See the X-3 Stilleto, an unsuccessful jet plane from 1952. Looks it was designed by George Lucas.)

Another factor is that they are hollow. The hollow sphere will have a very low sectional density, so they will have a low terminal velocity and will quickly decelerate enough that they won't burn themselves up. There wouldn't be a mystery if parachutes were landing.

As someone else pointed out, most of the re-entered objects that are reasonably intact are spherical tanks. They're one of the few components of a spacecraft that are very solidly built. Most are titanium, or titanium wrapped in Kevlar, so they can take re-entry temperatures. Spheres have good re-entry aerodynamics. Nose cones have been hemispherical since the late 1950, after it was discovered that pointy noses look cool but don't work well. (See the X-3 Stilleto, an unsuccessful jet plane from 1952. Looks it was designed by George Lucas.)

Its actually just sensationalism, as usual.
Look here at types and descriptions of reentered objects.
How many 'spheres' do you count?

The latest information I know of is listed here: http://reentrynews.aero.org/1991063b.html and it's usually about 12 hours out of date (at least that was the case few years ago).

Besides, moon shots with unmanned vehicles are pretty cheap, and probably comparable to the costs of developing the deep water surveying and placement technologies needed to set casks in subduction trenches.

Where do you get that moon shots are cheap? A Delta IV Heavy launch costs upwards of $300M, independent of the cost of the payload. Word on the street is that the real cost is something like $700M (big launch vehicles are heavily subsidized by the military. Shuttle launches cost something like $1B). SpaceX claims that they'll get that cost down to $60M for the equivalent of a DIV medium, but that won't go to the moon. I wish them the best, but I'll believe it when I can use my Visa Plutonium to make the deposit on one.

In addition, a not small percentage of these will fail. And rockets, like nuclear power plants, tend to work when they work, and fail spectacularly when they don't, and for the same reasons. Lots of energy in a small volume. Something between 7-10%. So every 15 launches, you get to write off a complete launch facility due to radioactive contamination (blowing up on the launch pad - best case), and a whole lot of downwind real estate (airburst - worst case).

Even in the best case, it ain't cheap to abandon a launch site - "the $4 billion SLC-6 was refurbished at a cost of about $300 million to accommodate Delta IV missions.".

Subduction zones don't seem like a great idea; too many unknowns, though I'd bet that undersea researchers would be thrilled to get a fraction of the cost of moon shot to explore the idea. The next generation deep sea submersible had an estimated cost of $21M in 2008.

Grandparent is right, these things were way overbuilt.

Grandparent needs to read more and I think you do too.

Launch Successes (s) and Failures (f), 1957–1999

With about a 6%-7% chance of failure of not even making it to the planet, you want to make as few launches as possible and get the most out of each.

Then you have everything that could go wrong during landing. e.g. Beagle 2 and the crater it left in the martian soil.

Yep, thank God NASA is run by actual rocket scientists rather than internet experts.

Nope Putting a huge radiator on your spacecraft will only get you so far.

it would not surprise me if the Saturn V's "small" pogo suppressors weighed over 1600 pounds in total.

The Saturn V is a much bigger rocket than Aries I.

The article is concerned mostly with military GPS, which is only slightly less susceptible to jamming than civilian GPS. The main weakness of GPS wrt jamming is that it's a very low power signal, usually clocking in at -160dBw. There's a good survey of the state of GPS antijam circa 2002 here.

"These people were not engineers or this would never have happened."

Engineers never have anything blow up or go wrong...

http://www.ov-10bronco.net/users/merlin/Flight/kaboom.htm
http://www.aero.org/publications/crosslink/winter2004/02.html

Areal view of what was believed to be the original impact site and Lake Cheko.

I'm no geologist so I can't comment on whether or not this lake looks typical but I will say that, judging by the coloration of the foliage around it, this is probable the same land as the river/stream that winds to the west of it. Interesting is that if you follow it northwest for miles it looks smooth cut. Once it passes Lake Cheko, it seems to become more speckled and pock marked. Doesn't seem 'natural' to me for an inlet and outlet to be positioned so close together on a lake--though the topography could indeed make that make sense if I could see a map of it.

I would guess this is quite feasible indeed to be part of whatever happened nearly 100 years ago. Check out the last page of this PDF which seems to show the comet/asteroid approaching at an angle (thus the strange blast pattern). At that trajectory, you'd think there'd be a chance for whatever hit to break apart and skip. Maybe the other abnormal marks in the stream are from other pieces/debris?

Probably fueled by the sci-fi stories written about the same topic (like the 1946 one by Alexander Kazantsev), I find it interesting to read about things like the Tunguska Genetic Anomaly whether they be true or not. Maybe these are the scientist's tabloids? :)

check out http://www.aero.org/capabilities/cords/debris-risk s.html

Second of all the, Mars' rovers spent considerable time in transit to Mars with no outside protection at all.

This page gives some good information on exactly what the effects are and what can be done about them.

Third of all while there is some protection offered by Mars, it is still much worse than anything on Earth.

And don't forget that the Mars rovers are controlled by computers. Computers are far more vulnerable to ionizing radiation than other forms of electronics. And really, ESCs are pretty simple, being mostly just analog components. They should be relatively resistant to ionizing radiation -- far more so than the computer components that control them. So I don't think that's really a big issue -- just protect them half as well as you protect the computer parts, and you'll be just fine. And also don't forget that the Mars rovers already almost certainly have several ESCs ... it's not like using brushless motors would add ESCs where there were none before.

... than underused shuttle facilities at KSC is the Air Force shuttle facility on the west coast, which cost $6 billion, and was never used at all.

"Having a say, and "dictating" are two different things. Only a small fraction of shuttle missions have been military-related. Having a few percent dictate the entire design would not be very rational."

Military mission needs contributed a great deal to the design of our current vehicle, and the Air Force was heavily involved in the process. In fact, the shuttle was about to start launching military missions from CA's Vandenberg Air Force Base when Challenger happened. Most people don't realize the amount of spending associated with the shuttle program that came from the military side:
http://www.aero.org/publications/crosslink/winter2 003/05.html

My mistake; twice a day (plus 1/365ths of an orbit). It would also be a huge menace since it would be plowing through the geosync belt, crashing into the world's most densely packed satellite constalations. Once it hit one unlucky bird, the debris from the collision would polute the entire belt with high speed projectiles, causing further destruction. Potentially ending in a chain reaction which leaves the entire orbit unusable for thousands of years. Please don't do this.

Our tanks have targetting systems that can see through smoke and lock onto targets miles away, our troops have glasses that can see at night, and I can go down to the local sporting goods store and buy a laser rangefinder that will accurately measure distances out to a mile or so with a margin of error of an inch or less ... but a SPACESHIP can't land because of a few clouds?

The shuttle can trigger lightning on a cloudy day.

This could easily disable electronic devices on-board.

Protecting Space Systems from Lightning article.

It will take years or decades for it to lose enough energy to fall back into the atmosphere. Considering that a paint fleck caused a 4mm crater in the windshield of a previous shuttle mission, leaving a few tons of trash floating around is a very bad idea.

^Satellite Orbital Analysts Toolkit^Satellite Orbital Analysts Program

STK = Satellite ToolKit, made by Analytical Graphics

Here is what an FFRDC is. I would actually love to work at Aerospace if it wasn't so fscking far away from me on the freeway... stupid SoCal.

Comparing that to Japan's main delivery system over the past few years, the ill fated H-2 and current H-2A design's combined 77% success rate with only 13 launches compared to the hundreds of US launches, and it's clear that most of the world has a huge leg up on Japan (including China) when it comes to space delivery.

I'm just concerned that Japan seems to want to leapfrog the manned space flight process altogether in favor of this whole automated robots with rocket delivery idea. There's a big technological gap between extended manned space flight (not to mention construction of space stations) and such and just firing rockets out into space.

ESA has a similar facility, as does NASA Goddard. And from what I've heard contractors like Boeing have experimented with the same kinds of ideas.

It would be nice if they'd find a way to repair or replace the Hubble Space Telescope, though.

Funny you should mention that. NPR's "Morning Edition" program reported this morning that NASA hired a company called The Aerospace Corporation to conduct a confidential study to determine the best way to deal with Hubble, including two completed instruments that were originally supposed to fly to Hubble aboard the Space Shuttle.

The conclusion? Well, the report itself is confidential and won't ever see the light of day. The executive summary, however, has been obtained through a FOIA request. In short, they don't think a robotic servicing mission could be completed before Hubble dies. They recommend flying a new bare-bones replacement for Hubble with the two new instruments onboard. In their opinion, it'll be cheaper and it's more likely to work.

Of course, there are those who dispute the study's findings. They say that there already exists a robot of sufficient dexterity for performing the mission. It was designed to fly on the ISS and last ten years. A Hubble service mission would last at most a few months.

I found this in a link from the "consequences" link in the story.

A shuttle windsield impacted by a paint chip at 3 to 6km/sec
http://www.aero.org/cords/debrisks.html

Wouldn't it be easier to just look up the failure rates published by Lockheed Martin

In a nutshell? EELV.

Yeah.. LM still does use kerosene. Cheaper is usually the prime value, especially in the competition for EELV. Which, by the way, is why Atlas II and IIAS are gone.

Oh, and burnoff from normal hydrazine is fatal, days later. That's why they have to scrub the pads at the Cape and Vandenberg between launches. O2's just a pain in the ass to store. Volatile stuff.

Seems they do about the same or even worse than cluster bomblets.

Um, not that I automatically disbelieve you or anything, but could you elaborate and/or cite some sources?

Here is an article.

Please note that I made no claim to the amount of ozone a single rocket launch depletes, it is fairly small. But rockets do destroy ozone, lots of rockets are launched every year, and the number of launches is undoubtedly going to increase as time goes on.

Interesting...I had never given that much thought until now. For anyone else who's interested, here's more info on rocket emissions.

Perhaps the intention is to emulate the practices that the DoD is trying to use to fix their space problems. But these practices have had limited implementation so far, and its not clear that they actually help at all. Besides, having seen first-hand how many DoD space programs (including some of extreme national importance) are run, I'm not sure that the DoD is necessarily the best model to be following. I won't even get into how idiotic the whole "systems-of-systems" buzzword/fad is.

As an aside, I wonder if one of the reasons for the commission's recommendation to spin off the NASA centers into FFRDCs is Aldridge's experience as the president of a space-focused FFRDC (The Aerospace Corporation).

Also, there's the GPS Primer from The Aerospace Corporation, whose engineers are largely responsible for the development of GPS.

Polar orbits, however, get little to no benefit from the location of the launch site.

Actually, for polar orbits it is kinematically better to launch further from the equator, since you don't need to fight the Earth's rotation. That's the reason that the US built a Space Shuttle launch complex at Vandenberg AFB. Space shuttles were never launched from there, partly due to the Challenger disaster.

We have a hard enough time tracking the breakup of stuff we left up there in the past.

Space travel is hazardous enough ... even without the odd orbital debris. Just the odd paint chip can make for a very bad day.

You don't need a high-explosive warhead. If you want to impact the comet, all you need is some mass and a lot of velocity. Look at the damage that was done to the shuttle windshield on a previous mission by a chip of paint.

Actually, the PPS transmits the P(Y) code on both L1 and L2. That's how the military gets better accuracy: the 2 different frequencies experience slightly different amounts of ionospheric delay, and by measuring this difference it's possible to correct for the delay.

more satellites in view = better positioning accuracy

This is not strictly true, since the position accuracy depends a lot on the relative position of the satellites you are taking a fix from (if they're all bunched up then you will experience significant dilution of precision). More satellites in view may increase the likelihood that you'll get a favorable geometric configuration. But it doesn't always, which is why the current GPS constellation is optimized to provide good geometric configurations, instead of to maximize the number of sats in view.

To make matters worse, some cheaper GPS receivers just grab data from the first 4 satellites they detect, and satellites that are directly overhead will have (slightly) stronger signals than their counterparts near the horizon as a result of the smaller amount of propagation loss and atmospheric loss their signals will experience. So there's a good chance that a cheap GPS receiver will take a fix from a bunch of satellites directly overhead (particularly with many more satellites in the sky to form that bunch), even if a more favorable configuration is in view, and end up with a much lower accuracy than they should. That said, I believe that most newer receivers look at all of the satellites in view, and pick the best 4.

Also GPS is being heavily upgraded. They are adding a third signal with M-code(L3), and adding C/A code on L2.

This isn't entirely accurate. M-code will in fact be on transmitted on both the L1 and L2 frequencies, not on L3. You're correct about the extra civilian signal on L2 (designated L2C), although I'm not sure if it's identical to the L1 C/A code. There's also another civilian signal that will be broadcast on L5 - this one will be primarily for aviation use and "safety-of-life" applications. I don't remember what L3 is being used for, but I'm fairly sure it's not going to have any kind of navigation code on it. Check out this article in the Aerospace Corporation's online "Crosslink" magazine for a nice overview of GPS modernization.

Material typiclly doesn't come from elsewhere in the solar system and get stuck in some system's L4 points (like the Earth-Moon L4 or L5 points). The material that is there, if any, would have existed in that location since the formation of the system, i.e., anything near the Earth-Moon L4 or L5 points was there when the Moon formed.

Regarding the killer asteroids, you're totally right about deflecting them with small forces. There will be a conference next year, Planetary Defense Conference: Protecting Earth from Asteroids, where people will propose technical plans associated with defending Earth from approaching near Earth objects (comets and asteroids). The threat will be approached from three warning levels: short-term (less than ten years warning); medium-term (ten to 30 years warning); and long-term (more than 30 years warning). The more time we have to deflect it, the smaller the force needs to be.

There's some info and a really cool animation (gif) at the Aerospace Corporation Site that gives a little sense of the amount of junk out there.
The Johnson Space Center orbital debris site used to have some nice graphics too, but it's currently out.

There's some info and a really cool animation (gif) at the Aerospace Corporation Site that gives a little sense of the amount of junk out there.
The Johnson Space Center orbital debris site used to have some nice graphics too, but it's currently out.

look, we proved it wasn't made of cheese. and unless they are sending mining robots, there's not a lot to see there. doing this for national pride seems a strange thing to do. they should pitch in and send up some parts for the space station. the plus side is you learn from every shot. also, how long before there is so much orbital debris that sending a ship into orbit is certain doom? more players in the space race means that near-space environmentalism maybe the new cause for students to cry about. just a thought

This discussion has come up before.

And before you get modded up further, small pieces of grit are capable of creating holes in the the space shuttle's windshield.

So what? All it takes is one lucky hit to destroy billions of $ of equipment. That is much more money than most lotteries. And anyway it happens much more frequently than you imply.
From this useful site:

"For example, NASA frequently replaces space shuttle orbiter windows because they are significantly damaged by objects as small as a flake of paint."

Last October, when Dr. Decyk and I presented at the Aerospace Corporation, we accidentally showed up late. There were a bunch of powered-off PBG3's in bags there we had just seen for the first time. We brought one Asante Ethernet switch and some cables.

10 minutes later, in front of the audience, we had those PB's working as a cluster, and we were ready to present. We were told the audience was impressed. I could forward you the emails of some of the Aerospace employees who witnessed us.

You are certainly welcome to try out the software for yourself.

Have fun,
Dean

P. S. As for getting work done, you may critique my dissertation at: http://dauger.com/DaugerDissertation.pdf All the data was computed, analyzed, and visualized on Macs.

The second significant peak will begin around 12 noon EST and last until 2 pm EST on the 18th of November. The best viewing for this peak will be over Australia and the Far East. The level of activity for this event could be anywhere from 7000 to 15000 meteors per hour!

Anybody who can corroborate..

Here's a site that is predicting a ZHR (zenith hourly rate) of meteors during the height of the shower on the order of 1000-3000. Works out to one a second or so - which while not totally amazing - would be a much higher rate than I've ever seen.

They've got two models and both seem to be in relative agreement. It all depends on how the Earth is oriented and moving through the comet trail and the exact geometry of the dust distribution in the trail. But what the heck - I've hung out before, maybe this will be my year to get lucky!

For those on the East Coast, it'll probably be worth getting up a little (okay - a lot) earlier than normal. Check out Leo in the Southeast sky (about 45 degrees above the horizon) around 5 AM in the morning. That should get you right around peak.

The rate should start to ramp up after midnight EST peaking just before dawn. Those to the west will get to see the decline.

The only problem for those on the west is that with the constellation of Leo being the radiant (hence the name) and Leo being low or below the horizon, they'll be missing most of the show. It's just as bad or worse in Europe this time around, since they'll be in daylight during the predicted max.

While the concers of the public are most liekly grounded in Hollywood science fiction they are no less improtant. Every day small pieces of space debris are able to survive re-entry. Most of this debris is too small to damage structures or living things, it also is concentrated in relatively uninhabited areas. Regardless, large pieces of Iriduim satellites reaching earth is a distinct possibility. Many municipaliteis have plans for just such an event, plans that have scientific justification. While the possibility of this is remote, it is certainly in our best interests to consider the possibility.

I'd say a two foot by three foot fuel tank has a good chance of hitting the ground. I've seen (and touched) a two foot titanium ball from a delta second stage. You can see pictures of things that have survived on my company's website.

Disclamer: I do not speak for The Aerospace Corporation in any capacity.

I'd say a two foot by three foot fuel tank has a good chance of hitting the ground. I've seen (and touched) a two foot titanium ball from a delta second stage. You can see pictures of things that have survived on my company's website.

Disclamer: I do not speak for The Aerospace Corporation in any capacity.

A few months ago I heard of a proposal by The Aerospace Corp to use lasers for just this purpose. The idea was to generate light pressure on debris objects to cause orbital decay, not to disintegrate them. The experiment mentioned by the BBC is likely a feasibility demonstration.