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Comment Re: The problem - taking off again (Score 1) 316

I think normal landing will be rockets only, and if they fail it will be too late to parachute, so they are already trusting the landing rockets in a safety critical role. The chutes are there for emergency escape during launch. In this case, the landing rocket fuel has been expended getting away from the exploding launcher.

Comment What can SpaceX do with their hardware? (Score 2) 316

I have considered before that the hardware SpaceX have or are building come quite close to supporting moon landing, and wondered how much of a gap there is and what it would take to bridge it. Unfortunately the article here is very light on detail and does not address my questions.

The Saturn V could put 140 tonnes into LEO. The Falcon Heavy will be able to put 55 tonnes into LEO. If you can split the Apollo hardware into three approximately equal bits, three FH launches could put them into orbit, then they rendezvous and head to the moon. You could probably use the existing second stage as a third stage to take the stuff from LEO to lunar orbit. (I couldn't quickly find the mass of a fuelled Falcon second stage, nor how much mass it could deliver to low lunar orbit.) You could use a Dragon in place of the Apollo command module. Whether you could use a second Dragon as the lunar lander is less clear.

Wikipedia ( says lunar surface to low lunar orbit requires 1.9km/s delta-v. If you wanted to land and takeoff with the same vehicle, that would be 3.8km/s. SpaceX are planning a 'Red Dragon' mission to land a Dragon capsule on Mars. Low Mars orbit to surface is 4.1km/s (assuming no aerobraking/parachuting) so Red Dragon should be able to land on the moon and return to orbit. However, Red Dragon is unmanned - I don't know whether you have space and mass budget to stuff some people and life support in there also.

The manned Dragon capsule has rockets allowing it to propulsively land - taking from terminal velocity falling through the atmosphere to zero velocity on a landing pad. I don't know how much delta-v this requires, but I expect much less than 3.8km/s.

(Falcon Heavy and manned Dragon capsule have been under development for some time and should fly this year. I don't know how advanced Red Dragon is, but they want to launch in 2020.)

Comment Tidal locking question (Score 1) 273

Low mass stars (and this one is very low mass) are dim, so the habitable zone is very close, so tidal effects of the star on the planet are large*, so under normal circumstances the planet will tidally lock to the star, which is not friendly to life. (Although I wouldn't go so far as to say life is impossible on a tidally locked world.)

If the planet has a large enough moon, it will lock to the moon instead, and avoid the star tidal lock (at least for a while.) So I imagine a planet and moon locked to each other and in close orbit around the star. In this case, what will happen to the planet/moon orbit as it gets perturbed by the stellar tides? Will it remain stable, or has the moon only bought me temporary reprieve from stellar tidal lock?

* Back of envelope tidal calculation:
Luminosity of star L proportional to mass of star M to 4th power (roughly)
Goldilocks orbital radius R proportional to sqrt(L), i.e. R propto M^2
Tidal strength T propto M/R^3 (it is derivative of M/R^2), so T propto M/M^6 = 1/M^5. (It is the 1/R^3 which allows a moon to out-tide the star, despite being very much less massive.)
News says this star is 2000 times fainter than the sun, so about 0.15 solar masses
So tidal effects of star on habitable planets is about 13,000 times greater than tidal effect of sun on earth.
The tidal effect of the sun on the earth are small but noticeable - it causes the difference between spring and neap tides.

Comment This would make it the 5th continent (Score 1) 142

If you are claiming that it isn't coastlines and land areas which make continents, but rather regions of continental rock (whether above sea level or not). If this is so, you can no longer justify counting Africa as separate from Eurasia, or North and South America being separate from each other. So you can pick between the traditional 6 continents by land area, or four or five by crustal rock (Eurasia+Africa, Americas, Antarctica, Australia, and Zealandia if you think it is big enough.)

Incidentally, New Zealand may have been almost entirely submerged 24 to 21 million years ago.
I don't know if there were any other major Zealandia land masses at the time.

Comment Ridiculous Slashdot story (Score 2, Insightful) 183

This is one of the lamest Slashdot articles I have ever seen. In what way is this at all news for nerds? And in what way is this any more news worthy than 10,000 other random news items of day? What about if Walmart has a one-day sale on Nintendo games. Should we get a Slashdot headline article for that?

msmash is not a competent Slashdot editor. I'm going to give Slashdot some feedback here.

Comment Re: Almost clever (Score 1, Flamebait) 62

... in a hamfisted manner has little to no chance of sticking. The man is dumb as a box of rocks, unfortunately. Despite all of his bluster he is apparently unable to operate with the required tact and subtlety necessary to effect changes he desires. There is the possiblity that everything he is doing publicly is a ruse to distract everyone and he is going to surprise us with the masterful maneuvers he's been making behind the scenes but ... given how dumb he has appeared to be at just about every opportunity, I doubt it.

When he won I was at first disgusted, then somewhat hopeful as I thought, maybe the guy, despite being scum, can actually effect some interesting and valuable changes to the status quo of politics, maybe he can make some meaningful things happen that others couldn't because of their political ties.

But seeing how hamfisted he's been in everything he's tried, and failed thus far, to do ... I am holding out little hope at this point.

Comment Re:Oh the irony. (Score 1) 359

Also may I point out that the word "eliminate" was just the wrong term to use full-stop because of the ambiguity that it introduces. No need for that ambiguity, but clearly the author was going more for "impact" than for clarity. Something like:

"How UPS Trucks Saved Millions of Dollars By Preferring Right Hand Turns"

would have been clearer and then we wouldn't even be having this pointless discussion.

Comment Re:Oh the irony. (Score 1) 359

Yeah, this is why in English we use disambiguating terms like "some" and "all". No soldier speaking english would ever say "I've eliminated enemy combatants", they'd say, "I've eliminated SOME enemy combatants". And I agree with your assertion that the "the" in my example was disambiguating.

However, we all know that article titles generally do not use articles in the same way, for brevity's sake, which is why choosing an ambiguous wording as the article did, is a bad idea, and why it leads to confusion where some people interpret it one way and some the other way.

My main beef was with you calling people 'idiot' because they were misled by an ambiguous title and then pointed out what was ambiguous about it, as if your personal interpretation of ambiguity was somehow the "correct" interpretation and anyone who reads it a different way is an "idiot".

Really alot of it comes down to hating to read people immediately start out with name-calling, and it seemed ironic since the person you are responding to had a valid point, which I have just elucidated.

But whatever, have a good day.

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