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m1omg
2007-Aug-27, 04:55 AM
What is the maximum acceleration that probe can withstand?

cjl
2007-Aug-27, 05:09 AM
That entirely depends on the design of the probe. Currently, most probes do not need to withstand more than about 5-7 gees, and are designed accordingly. However, there are electronics used in artillery shells, taking many thousands of gees. Of course, they are far heavier and more expensive than a similarly capable item that was only made for a few gees.

Launch window
2007-Aug-27, 05:12 AM
Missile heads, fired at targets can penetrate material with a g-forces close to 300 g's, whether or not the scientific equipment inside the missile head can 'survive' the impact is another matter.

Most high tech equipment is easily damaged by impacts, that's why space agency's prefer soft-landed spacecraft

tlbs101
2007-Aug-27, 05:29 PM
When we are contracted to provide avionics for space-flight, we are required to test the equipment to several 10s of gees, depending on the customer requirements.

The highest level we have tested to recently is 55 g RMS from 1 Hz to 2 kHz. Typically, the customer wants 20 - 25 g.

These avionics 'boxes' are inside the launch vehicles.

Typically probe avionics have a slightly reduced g-load because they are carried in a sort-of 'cradle' and it reduces the g-forces of launch.

Sometimes we test to failure, also. These levels are still in the 10s of gees for probe avionics, so that would dictate the ultimate force a probe could withstand. 30-50 g would be a good, typical estimate as an answer to your question.
.

joema
2007-Aug-27, 05:31 PM
The Deep Space 2 Mars microprobes were designed to impact Mars' surface at over 400 mph and function afterwards. Estimated g forces range from 30,000 g to 80,000 g.

http://www.solarviews.com/cap/craft/ds2.htm
http://www.ghg.net/ritakarl/probe.html
http://en.wikipedia.org/wiki/Deep_Space_2

Unfortunately the carrier vehicle itself may have malfunctioned, taking the microprobes with it: http://pweb.jps.net/~gangale/opsa/mars/MarsPolarLander.htm

However from "smart" artillery shells, the above microprobe tests, etc. we know it's possible for properly-designed electronics to withstand several thousand g's: http://en.wikipedia.org/wiki/M712_Copperhead

mugaliens
2007-Aug-30, 10:54 AM
Thanks, joema - you beat me to it.

Yes, and deep-penetration warheads can withstand quite a bit, as well.

Drbuzz0
2007-Sep-01, 12:37 AM
It depends on how long you're talking about. Even humans can withstand enormous g-forces for a brief pulse, if properly restrained.

Are you talking like a microscecond of G's from a collision or being fired from a gun or something or are we talking an appreciable period of time, like several minutes of acceleration?

mugaliens
2007-Sep-01, 11:27 AM
It depends on how long you're talking about. Even humans can withstand enormous g-forces for a brief pulse, if properly restrained.

Are you talking like a microscecond of G's from a collision or being fired from a gun or something or are we talking an appreciable period of time, like several minutes of acceleration?

Yes, like about 20 without injury, about 100 without dying.

We're talking on the order of 50,000 Gs, here.

joema
2007-Sep-01, 01:02 PM
Are you talking like a microscecond of G's from a collision or being fired from a gun or something or are we talking an appreciable period of time, like several minutes of acceleration?
The OP asked about maximum acceleration a space probe can withstand.

There are two ways to evaluate this:

(1) Negative acceleration (deceleration) as when landing without parachute or braking thrust. This can be very high -- around 50,000 g, but for a short period. From 400 mph, the Mars Deep Space 2 microprobes decelerated within about 1 millisecond. A properly designed space probe (or other electronic systems) can survive that.

(2) Positive acceleration from rocket thrust. This is limited by available thrust, which isn't much. If properly designed space probes can survive 50,000 g, they can obviously survive 10g sustained acceleration on a rocket.

To further illustrate this, a past antiballistic missile prototype called HIBEX accelerated at about 400 g, yet the on board electronics functioned: http://designation-systems.net/dusrm/app4/hibex.html

The Nike Sprint missile accelerated at about 130 g. Supposedly it accelerated to 3,600 mph within TEN FEET. It was electronically guided from the ground. so could obviosly endure that. It was succesfully test launched many times.

http://upload.wikimedia.org/wikipedia/commons/a/a2/Meck6.jpg
http://video.google.com/videoplay?docid=-5182850449033471260&q=sprint+missile&total=9&start=0&num=10&so=0&type=search&plindex=4
http://www.youtube.com/watch?v=nLpLEgAS574
http://srmsc.org/video/005017m0.wmv

Drbuzz0
2007-Sep-01, 10:17 PM
The OP asked about maximum acceleration a space probe can withstand.

There are two ways to evaluate this:

(1) Negative acceleration (deceleration) as when landing without parachute or braking thrust. This can be very high -- around 50,000 g, but for a short period. From 400 mph, the Mars Deep Space 2 microprobes decelerated within about 1 millisecond. A properly designed space probe (or other electronic systems) can survive that.

(2) Positive acceleration from rocket thrust. This is limited by available thrust, which isn't much. If properly designed space probes can survive 50,000 g, they can obviously survive 10g sustained acceleration on a rocket.

To further illustrate this, a past antiballistic missile prototype called HIBEX accelerated at about 400 g, yet the on board electronics functioned: http://designation-systems.net/dusrm/app4/hibex.html

The Nike Sprint missile accelerated at about 130 g. Supposedly it accelerated to 3,600 mph within TEN FEET. It was electronically guided from the ground. so could obviosly endure that. It was succesfully test launched many times.

http://upload.wikimedia.org/wikipedia/commons/a/a2/Meck6.jpg
http://video.google.com/videoplay?docid=-5182850449033471260&q=sprint+missile&total=9&start=0&num=10&so=0&type=search&plindex=4
http://www.youtube.com/watch?v=nLpLEgAS574
http://srmsc.org/video/005017m0.wmv


Right, I understand the OP means acceleration, but does that mean acceleration as in a rocket (somehat continuous I would assume) vrs acceleration by a strong impulse, such as being fired from a cannon or some sort of confined explosion engine.

There will obviously be a limit to how many G's you can exert from acceleration over a long period of time by how much energy you have. Your tanks will run dry pretty fast if you're accelerating enough to be doing 500 G's.

mugaliens
2007-Sep-01, 10:24 PM
The Nike Sprint missile accelerated at about 130 g. Supposedly it accelerated to 3,600 mph within TEN FEET.

I've seen more than my fair share of videos on it and I'm still amazed!

This is my favorite video (http://www.youtube.com/watch?v=XpDJ2WBWm0E), though.

Drbuzz0
2007-Sep-01, 10:52 PM
I've seen more than my fair share of videos on it and I'm still amazed!

This is my favorite video (http://www.youtube.com/watch?v=XpDJ2WBWm0E), though.

Yeah you gotta love the Sprint launch. It looks like it's from Benny Hill, sped up to comical speeds... but no.. that is actually the real time film.

Amazing piece of technology. It was only in the inventory for a short time. It was realized that it would be very difficult to hit an ICMB so the sprint and spartan carried nuclear warheads which would destroy any within the area by blast and hopefully even tragets a few miles or more away by the neutron and X-ray flux.

But then it was decided that it wasn't a good idea to intercept nukes with nukes, because you could ruin satellites and cause fallout problems, and possibly a geomagnetic storm which would damage the power grid and sensative radio receivers and also make it impossible to get decent AM reception.

So instead they were taken out of service, that way we wouldn't have to worry about all the radio stations knocked off the air and all the satellites damaged and the possibility of fallout entering the atmosphere because we'd all have been converted to a superheated gas when they blow up in the cities instead of the mesosphere.

cjl
2007-Sep-02, 02:40 AM
The Nike Sprint missile accelerated at about 130 g. Supposedly it accelerated to 3,600 mph within TEN FEET. It was electronically guided from the ground. so could obviosly endure that. It was succesfully test launched many times.
As cool as that sounds and all, the reality is slightly different. Yes, 130g is VERY fast, but not enough to get to 3600mph in ten feet. I've launched one rocket that accelerated at a constant 60g, and it still took 310 feet to reach mach 1, at only 760mph. At 130g, it would be going roughly 210mph in 10 feet, 360mph in 30 feet, 1400mph in 500 feet, and 2050mph in 1000 feet. It wouldn't reach 3600mph until around 3000 feet up. That's still incredible though :cool:

joema
2007-Sep-02, 12:47 PM
Thanks for pointing that out. I saw a reference stating that, but you're right, it's impossible.

Even if Sprint 1st stage acceleration was a sustained 130 g, this wouldn't remotely reach 3,600 mph in 10 feet.

However it's still impressive. 130 g equates to 4,186 ft/sec/sec (1275 m/sec/sec) acceleration. This would do:

- 0-60 mph in 20 milliseconds
- Mach 1 in about 130 feet
- 1/4 mile elapsed time: 0.79 sec @ 2,254 mph

Count Zero
2007-Sep-03, 02:24 AM
I'd be more inclined to believe the 3,600 mph in 10 feet over the 130 G figure. In the Navy we had SAMs (SM2ER, iirc) that would clear the rail at over Mach 1.

Count Zero
2007-Sep-03, 02:27 AM
I've seen more than my fair share of videos on it and I'm still amazed!

This is my favorite video (http://www.youtube.com/watch?v=XpDJ2WBWm0E), though.

Too bad the video stopped so soon. In the extended version of that film, after a few seconds you can see the Sprint turn white-hot from its passage through the atmosphere. :eek:

cjl
2007-Sep-03, 03:20 AM
I'd be more inclined to believe the 3,600 mph in 10 feet over the 130 G figure. In the Navy we had SAMs (SM2ER, iirc) that would clear the rail at over Mach 1.

Knowing rockets, I would be more inclined to believe that whoever told you that they clear the rail at mach 1 is wrong. Getting a rocket to accelerate at those kinds of values, even "just" at 100g, is a tremendous feat, as it involves very high thrust yet lightweight motor designs. The highest I've ever heard of a solid rocket achieving was roughly 320g right at the end of the burn, when the rocket (which was pure carbon fiber and barely thick enough to take the forces) was lightest and had almost no fuel left. The casing of the motor was run at about 5% below its pressure limit, and everything on the rocket was barely able to take it. With some slight modifications and a LOT of testing, this might hit a little higher, but 3600mph in 10 feet (43,000 gees) is completely out of the question. For that matter, hitting mach 1 in less than about 30-40 meters is out of the question too, unless it literally used an explosive charge (no, I don't mean a rocket, but like a gun or a high explosive) to propel it off the rail.

Count Zero
2007-Sep-03, 09:32 AM
Knowing rockets, I would be more inclined to believe that whoever told you that they clear the rail at mach 1 is lying.

Excuse me, but when did the antonym of "correct" become "lying"? Has it become inconceivable that someone may simply be wrong? Is it somehow satisfying to create moustache-twirling villains out of people you haven't met, and who cannot defend themselves? Shame on you.

That said, he may well have been wrong. I haven't done the calculations. To his credit, he was a GMM (Gunner's Mate - Missiles) on USS Mahan when they were the test-ship for the SM2ER in the '80s, so his job was the care, maintenance and loading (but not firing) of these missiles. At the time, I was inclined to believe him because I had seen an SM1ER launch just a short while earlier (from <200 feet away), and its acceleration was faster than I could follow.

Looking around, I can't find acceleration data on the SM2ER, but I did find this (http://ed-thelen.org/) site, which talks about the Nike-Hercules missile. This bird was much larger than the SM2ER, but they had a lot in common. Both missiles followed plotted-intercept paths and had comparable ranges in this profile. Both were 2-stage missiles with a high-acceleration booster that burned-out after a few seconds, and a slower-burning sustainer. According to the above site, the Nike-Herc accelerated at 25 Gs, and was moving at 1,700 mph (straight-up, which the SM2ER did not do) after 4.4 seconds. It seems reasonable to assume that the SM2ER would have had similar performance.

cjl
2007-Sep-03, 05:55 PM
OK, sorry. That was an unintended negative tone. I meant for it to be a neutral "was wrong," but forgot to read it before posting to check.

As for incredible acceleration, that I definitely would believe. Here's a rocket accelerating at about 70 or 80 gees:

http://www.youtube.com/watch?v=FpZUXJ3aTxk

That one still didn't reach mach for about 150-200 feet. Definitely impressive though.

Grashtel
2007-Sep-03, 08:44 PM
Looking around, I can't find acceleration data on the SM2ER, but I did find this (http://ed-thelen.org/) site, which talks about the Nike-Hercules missile. This bird was much larger than the SM2ER, but they had a lot in common. Both missiles followed plotted-intercept paths and had comparable ranges in this profile. Both were 2-stage missiles with a high-acceleration booster that burned-out after a few seconds, and a slower-burning sustainer. According to the above site, the Nike-Herc accelerated at 25 Gs, and was moving at 1,700 mph (straight-up, which the SM2ER did not do) after 4.4 seconds. It seems reasonable to assume that the SM2ER would have had similar performance.
From the length given on the Wikipedia page for the SM-2ER (http://en.wikipedia.org/wiki/Standard_missile) is correct and that the launcher shown is a standard one then the launcher is no more than about than 10m long so the missile would have to accelerate at something like 6,000g to reach mach one before leaving it.

Count Zero
2007-Sep-04, 12:35 AM
Mathematics triumphs over rumor once again! Thanks guys. I hate putting out bum dope.