# We can hit a 23,000 MPH comet with a probe but we couldn't pull off Star Wars? **URL:** \ **Category:** Factual Questions\ **Created:** [July 4, 2005, 2:51pm UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016 "2005-07-04T14:51:45Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Jurph](https://avatars.discourse-cdn.com/v4/letter/j/50afbb/32.png) [@Jurph](https://boards.straightdope.com/u/Jurph)\ **Post date:** [July 11, 2005, 2:40pm UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/21 "2005-07-11T14:40:33Z")
> [@Little Nemo](#): > > ICBM’s travel at 6 to 7 km/sec. Somewhere between 21600 to 25200 kph. A Soviet Topol ICBM is about 21 meters long and 2 meters in diameter. Sure, the missile is 21 meters long. But the boost stages comprise about 90% of that length, and are gone within the first 5 minutes of flight. For the other 25+ minutes, it’s mostly drifting, with the post-boost vehicle making tiny course corrections for a few more minutes in the ascent (possibly even “faking” towards Target A and then changing course towards Target B). Once the reentry vehicle is spun up and released, it free-falls up to apogee and then back down to the target. Not much heat signature to track until it begins to reenter. The reentry vehicle is very small - a cone that has roughly the height and girth of a professional (American) football player. It’s moving _very_ fast, and probably traveling in formation with a few decoys, jammers, chaff, and other distractions. Imagine trying to hit a baseball pitched to you in a blizzard, while five or six guys stand near the pitcher and throw snowballs to the catcher at the same time. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [July 11, 2005, 3:00pm UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/22 "2005-07-11T15:00:22Z")
Again, each missile may contain several re-entry vehicles. And each of those RVs may have ‘penetration aids’ intended to help them foil interception, and some of them may be decoys. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [July 11, 2005, 5:29pm UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/23 "2005-07-11T17:29:12Z")
> [@](#): > > Sure, the missile is 21 meters long. But the boost stages comprise about 90% of that length, and are gone within the first 5 minutes of flight. The length really is the primary factor anyway. Nobody would try to intercept a missile from the side; your “best” chance would be to aim along the path of flight. So you’ve got one missile flying along at 15000 mph aiming to hit a six foot wide target that’s also traveling at 15000 mph. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [July 11, 2005, 5:30pm UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/24 "2005-07-11T17:30:41Z")
That should have been “really isn’t” not “really is”. ---
**Author:** ![Soylent\_Gene](https://avatars.discourse-cdn.com/v4/letter/s/ecae2f/32.png) [@Soylent\_Gene](https://boards.straightdope.com/u/Soylent_Gene)\ **Post date:** [July 11, 2005, 7:02pm UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/25 "2005-07-11T19:02:15Z")
Something that made the comet impact easier was that the Deep Impact probe was in the same trajectory as the comet. The collision was attained by the speed difference of the two objects. The Comet merely over-took the probe, kind of like a really bad rear-ender. This is a lot easier collision to manage than if they were trying to cross paths like an ABM and an ICBM. ---
**Author:** ![Pushkin](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@Pushkin](https://boards.straightdope.com/u/Pushkin)\ **Post date:** [July 11, 2005, 11:43pm UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/26 "2005-07-11T23:43:15Z")
> [@Stranger On A Train](#): > > It’s a shame, really; lacking sufficient backing and inability to set reasonable timelines means that billions of dollars spent upon the system are a waste, while deploying _any_ system still encourages opponents to do all they can to defeat or overwhelm it. So, it doesn’t work AND it makes the situation worse. Good call Interesting post and links. But I still can’t stand reading that an ABM system won’t stop ships with nuclear devices on board coming into harbour and blowing up a coastal city etc surely noone claimed it would? 😕 ---
**Author:** ![Tuckerfan](https://avatars.discourse-cdn.com/v4/letter/t/eada6e/32.png) [@Tuckerfan](https://boards.straightdope.com/u/Tuckerfan)\ **Post date:** [July 12, 2005, 12:45am UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/27 "2005-07-12T00:45:45Z")
> [@Pushkin](#): > > Interesting post and links. > > But I still can’t stand reading that an ABM system won’t stop ships with nuclear devices on board coming into harbour and blowing up a coastal city etc surely noone claimed it would? 😕 No, but the threat for a nuclear attack is most likely going to come from a shipboard nuke and **not** from an ICBM. ---
**Author:** ![NillyWilly](https://avatars.discourse-cdn.com/v4/letter/n/3da27b/32.png) [@NillyWilly](https://boards.straightdope.com/u/NillyWilly)\ **Post date:** [July 12, 2005, 1:23am UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/28 "2005-07-12T01:23:02Z")
Why do you say that an attack is most likely to come from a shipboard nuke? Are you including submarines in that category? ---
**Author:** ![Tuckerfan](https://avatars.discourse-cdn.com/v4/letter/t/eada6e/32.png) [@Tuckerfan](https://boards.straightdope.com/u/Tuckerfan)\ **Post date:** [July 12, 2005, 1:30am UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/29 "2005-07-12T01:30:51Z")
> [@NillyWilly](#): > > Why do you say that an attack is most likely to come from a shipboard nuke? Are you including submarines in that category? The only nations with nuclear weapons that have a beef with the US are Iran and North Korea (though there’s some doubt if they actually have any nukes yet or not). Neither one of them is currently capable of lobbing a nuke at the US via an ICBM. NK supposedly is close to having the ability, but its doubtful that even if they actually do have a missile with the necessary range, that it could be successfully fired. Given that neither of those two nations can do it, then there’s really **nothing** for us to worry about, so far as ICBMs or submarine launched missiles go. ---
**Author:** ![Si\_Amigo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/si_amigo/32/2877_2.png) [@Si\_Amigo](https://boards.straightdope.com/u/Si_Amigo)\ **Post date:** [July 12, 2005, 1:49am UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/30 "2005-07-12T01:49:07Z")
> [@NillyWilly](#): > > Why do you say that an attack is most likely to come from a shipboard nuke? Are you including submarines in that category? I think that he is saying that it will be carried on some obsure frieghter that docks into or near a major harbor. Much more realstic and feasible than a missle attack. Think low tech. ---
**Author:** ![TokyoBayer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tokyobayer/32/13989_2.png) [@TokyoBayer](https://boards.straightdope.com/u/TokyoBayer)\ **Post date:** [July 12, 2005, 3:46am UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/31 "2005-07-12T03:46:31Z")
> [@Tuckerfan](#): > > The only nations with nuclear weapons that have a beef with the US are Iran and North Korea (though there’s some doubt if they actually have any nukes yet or not). Neither one of them is currently capable of lobbing a nuke at the US via an ICBM. NK supposedly is close to having the ability, but its doubtful that even if they actually do have a missile with the necessary range, that it could be successfully fired. Given that neither of those two nations can do it, then there’s really **nothing** for us to worry about, so far as ICBMs or submarine launched missiles go. Please feel free to speak for yourself. Some of **us** live within NK’S missile range. :mad: As mentioned above, decoys and other countermeasures are a major factor. Look at how well flares, chafe, etc. do against heat seeking missiles. ---
**Author:** ![Tuckerfan](https://avatars.discourse-cdn.com/v4/letter/t/eada6e/32.png) [@Tuckerfan](https://boards.straightdope.com/u/Tuckerfan)\ **Post date:** [July 12, 2005, 3:55am UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/32 "2005-07-12T03:55:29Z")
> [@TokyoPlayer](#): > > Please feel free to speak for yourself. Some of **us** live within NK’S missile range. :mad: IIRC, they haven’t had much luck with their missiles which are supposed to be able to hit Japan, either. Not that I like the thought of Japan getting nuked. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 12, 2005, 4:30am UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/33 "2005-07-12T04:30:01Z")
> [@](#): > > Please feel free to speak for yourself. Some of us live within NK’S missile range. And it would therefore be perfectly reasonable for Japan to consider implementing a missile-defense system. Reasonable to consider it, though not necessarily to do it: That would depend on the likelihood of an attack, the cost of the system, and the expected likelihood that the system would work. But it’s completely unreasonable for the U. S. to consider such a system, because there are no threats to the U. S. which would be addressed by such a system even if it worked, and it distracts attention away from other much more plausible threats. ---
**Author:** ![TokyoBayer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tokyobayer/32/13989_2.png) [@TokyoBayer](https://boards.straightdope.com/u/TokyoBayer)\ **Post date:** [July 12, 2005, 5:02am UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/34 "2005-07-12T05:02:33Z")
> [@Tuckerfan](#): > > IIRC, they haven’t had much luck with their missiles which are supposed to be able to hit Japan, either. Not that I like the thought of Japan getting nuked. Believe me, if you don’t like the thought of Japan getting nuked, I’m much less pleased. Their accuracy isn’t great yet, but they’ve launched a missile over Japan in the past. Coming from a certified crazy country, that’s not something to be taken lightly. I don’t believe that the current method is a good approach, but something must be considered. IIRC Japan and the US are working on a joint missile defence program separate from the Son of Star Wars approach. ---
**Author:** ![NicePete](https://avatars.discourse-cdn.com/v4/letter/n/ee7513/32.png) [@NicePete](https://boards.straightdope.com/u/NicePete)\ **Post date:** [July 12, 2005, 5:11am UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/35 "2005-07-12T05:11:04Z")
Dang, you guys can politicize _anything_, can’t you? Did not RTFT, but a missle is moving in atmosphere. A comet is moving a vacuum and is therefore infinitely more predictable. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [July 12, 2005, 6:48am UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/36 "2005-07-12T06:48:04Z")
> [@Stranger On A Train](#): > > Er, please cite. To my knowledge, no full-up test of the GMD (Ground-based Midcourse Defense) system has even been conducted, much less successfully. I read about nifty Star Wars laser stuff, not any of that wimpy ground-based missile stuff. [“In November 2004 all six modules of the COIL laser were successfully fired for the first time. The COIL laser is to be installed in late 2005. The first prototype is scheduled for completion in 2006. A second system is being considered for 2008.”](http://www.airforce-technology.com/projects/abl/) ---
**Author:** ![Pushkin](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@Pushkin](https://boards.straightdope.com/u/Pushkin)\ **Post date:** [July 12, 2005, 10:27am UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/37 "2005-07-12T10:27:14Z")
> [@Tuckerfan](#): > > No, but the threat for a nuclear attack is most likely going to come from a shipboard nuke and **not** from an ICBM. I know, but its still a peeve of mine when someone points out that a space based laser or ground based missle system won’t be sniffing around freighters in mid atlantic or pacific. That’s what the Navy, Coastguard, Intelligence services will be doing. Its sort of liked doing away with police speed traps because they do nothing for burgularies. I know, its probably not the same sort of thing and I realise SDI is a bit far fetched for decades if not longer, but when there’s ample evidence that its a bit of a dead donkey why mention shipboard nukes? Sorry, like I said, its a peeve of mine 🙂 ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [July 12, 2005, 1:51pm UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/38 "2005-07-12T13:51:02Z")
> [@Sage Rat](#): > > I read about nifty Star Wars laser stuff, not any of that wimpy ground-based missile stuff. > > [“In November 2004 all six modules of the COIL laser were successfully fired for the first time. The COIL laser is to be installed in late 2005. The first prototype is scheduled for completion in 2006. A second system is being considered for 2008.”](http://www.airforce-technology.com/projects/abl/) From your cite: [indent]_The ABL is designed to detect and destroy theatre ballistic missiles in the powered boost phase of flight immediately after missile launch. The aircraft loiters at an altitude of 40,000 feet._[/indent]The ABL is a _theater defense systemn_ designed to operate on a battlefield in close proximity to the launch site, knocking out the missile in boost phase by firing at the booster, rupturing the case and igniting the propellent. It is not effective against terminal-phase RVs and is a whole 'nother animal as compared to _strategic_ defense like KEI and GMD. In order destroy an ICBM, you’d have to have a plane up at the right time and within line of sight of the booster trajectory; difficult, if the launching party is, say, China or India. > [@Pushkin](#): > > I know, but its still a peeve of mine when someone points out that a space based laser or ground based missle system won’t be sniffing around freighters in mid atlantic or pacific. That’s what the Navy, Coastguard, Intelligence services will be doing. The point of that line of argument is that even if we did have an effective way to respond to a strategic attack (a massive flight of missiles headed to every destination to which Northwest flies in the continental US) it would merely cause a nation or party interested in a terrorist attack to pick a different vector, even assuming the option of a missile was possible to begin with. Sailing a weapon in on a boat is trivial; boats enter and leave American waters regularly, usually without so much as a by-your-leave. Requirements of registration with port authorities and Coast Guard approval are difficult to enforce. Shipping one over as, say, a shipment of electronics or Bebe shirts or rice is almost as easy. And as **Tuckerfan** astutely notes, the parties most interested in potentially doing us harm lack the reliable capability to send one via air, anyway. In the case of Iran and North Korea, though, I’d personally be more concerned about living in Syria or South Korea (or Japan), respectively, than I’d spend time worrying about their striking at the US. 'Course, that’s a reasonable assessment, and neither of those nations is known to be operated by reasonable leadership. ☹ > [@Chronos](#): > > But it’s completely unreasonable for the U. S. to consider such a system, because there are no threats to the U. S. which would be addressed by such a system even if it worked, and it distracts attention away from other much more plausible threats. Well, there’s Canada… 😉 Whenever this discussion comes up I can’t help but get the urge to quote from the film _Wag The Dog_: Stanley Motss: The President will be a hero. He brought peace. Connie Brean: But there was never a war. Stanley Motss: All the greater accomplishment. Stranger Albania’s hard to rhyme ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [July 12, 2005, 2:40pm UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/39 "2005-07-12T14:40:32Z")
> [@Stranger On A Train](#): > > [indent]_The ABL is designed to detect and destroy theatre ballistic missiles in the powered boost phase of flight immediately after missile launch. The aircraft loiters at an altitude of 40,000 feet._[/indent]The ABL is a _theater defense systemn_ designed to operate on a battlefield in close proximity to the launch site, knocking out the missile in boost phase by firing at the booster, rupturing the case and igniting the propellent. It is not effective against terminal-phase RVs and is a whole 'nother animal as compared to _strategic_ defense like KEI and GMD. In order destroy an ICBM, you’d have to have a plane up at the right time and within line of sight of the booster trajectory; difficult, if the launching party is, say, China or India. Not a debate on the feasibility–but rather a GQ of why we could hit something moving fast in one instance and not another; both given modern computer processing power. We did have successful tests knocking down very fast stuff–and a large part of that is probably because of modern computer processing power. So things _have_ improved from what the OP remembered on that front. ---
**Author:** ![Pushkin](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@Pushkin](https://boards.straightdope.com/u/Pushkin)\ **Post date:** [July 12, 2005, 3:51pm UTC](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016/40 "2005-07-12T15:51:27Z")
> [@Stranger On A Train](#): > > The point of that line of argument is that even if we did have an effective way to respond to a strategic attack (a massive flight of missiles headed to every destination to which Northwest flies in the continental US) it would merely cause a nation or party interested in a terrorist attack to pick a different vector, even assuming the option of a missile was possible to begin with. But, when we’ve sealed off all the ports and harbours, _then_ you’ll be wishing you had your ABM, won’t you! Seriously though, I get all the points made, its just a peeve of mine that the obvious fallacies of any sort of SDI at the moment seem to be enough by themselves without having to discuss alternative methods of warhead delivery. [Previous page](https://boards.straightdope.com/t/we-can-hit-a-23-000-mph-comet-with-a-probe-but-we-couldnt-pull-off-star-wars/311016.md?page=1)