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The Private Spaceflight Thread (SpaceX, Blue Origin, etc.)


Old Man

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I think a 200 passenger Mars rocket would have to be a vehicle on the order of 5-10 kilotons, and the rocket necessary to boost it past LEO probably several times larger than that. So, basically the size of an aircraft carrier or skyscraper.

 

So... on the scale of a Saturn V, which is what Musk proposed?

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So... on the scale of a Saturn V, which is what Musk proposed?

Well, the Saturn V could boost around 140 tons into low earth orbit. What I'm saying is that, to move 100-200 passengers from Earth to Mars, you probably need to boost a 5-10kt payload from the ground to LEO, so that would be dozens of times larger than a Saturn V if you launch from the ground as one unit.

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42 Raptor engines in the first stage!

 

Gaaaaaaaaah. Don't do that. Read up on the N1. Ganging many small motors is a complexity like n!. Small numbers of much larger engines, though it frontloads the engineering challenges into making those big motors, is the only real path.

The N1 suffered from various development problems, starting with being rushed and underfunded.

https://en.wikipedia.org/wiki/N1_(rocket)#Development_problems

 

When edison had failed about 200 times to build a Lightbuld he said:

"I did not fail 200 times. I just found 200 ways not to build one."

Sometimes the only way to get something done is trial and error. Just make certain the error does not (literally) blow up in your face.

 

and I would _totally_ believe them,

 

 

 

if they'd done a single thing in the last decade to demonstrate that they were truly interested.

Nasa would love to make a manned mission. If they just had the Budgetary security to actually do it...

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He said, "I'll just take out a patent on Joseph Swan's lightbulb! He'll never risk suing in an American court if I offer him a licensing deal!"

 

Self-described heroic inventor are far more likely to be patent trolls than "innovators."  

Interesting. Was not aware of that story:

https://en.wikipedia.org/wiki/Joseph_Swan#Independent_from_Edison

 

Edison was not without his mistakes in the end. He also regretted staying on DC over AC all this time:

https://en.wikipedia.org/wiki/War_of_Currents

 

Still my core message holds:

Failure is the ingredient for Success. The nesseary step that has to be taken before you succeed.

The failures of the N1 should not tell us the general idea is bad. We have yet to see a properly funded, modern attempt to make it work.

The N1 was a failure, that does not mean every further attempts at "many small engines" are inherently doomed or "badwrongfu".

http://www.businessinsider.com/successful-people-who-failed-at-first-2015-7

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Interesting. Was not aware of that story:

 

"The common coupling of Swan's name with that of Thomas Edison in connection with the incandescent electric lamp has often led to the notion that Swan collaborated with Edison in this invention. That was not so. Their work was completely independent, and although each knew the other was working on the problem of devising a practical lamp, they had neither met nor communicated with each other. The conjunction of their names came about in 1883 when the two competing companies merged to exploit both Swan's and Edison's inventions"

 

This is one of those weird Wikipedia conjunctions where the mandate to present the commonly accepted scholarly position leads to whiplash between paragraphs.

 

Wikipedia continues: 

 

"In America, Edison had been working on copies of the original light bulb patented by Swan, trying to make them more efficient. Though Swan had beaten him to this goal, Edison obtained patents in America for a fairly direct copy of the Swan light,[25][26] and started an advertising campaign that claimed that he was the real inventor. Swan, who was less interested in making money from the invention, agreed that Edison could sell the lights in America while he retained the rights in the United Kingdom."

 

How do we reconcile these two positions?Well, Edison did steal Swan's lightbulb. Not that this makes Swanany kind of hero. Swan had been experimenting with light bulbssince 1850. (Thomas Edison was three years old at the time.) However, he was experimenting with it because there was already a half-century or more of pioneering research in the area, and an entire industry of "safety lamps" for coal miners to fall back on. Swan's carbon filament-in-an-evacuated-glass-bulb was basically a fairly obvious solution to getting light out of something that kept the heat and sparks hermetically sealed away from the coal damp.

 

From there you get to the point where  you have an illumination method that's more practical than the gaslight competition. After that, the issue was market share. It was by this time abundantly clear that if you wanted to get into the American market, you needed an American collaborator, who would take out a patent on the invention. These American collaborators had an amazing ability to win patent law suits in American courts. There were American inventors who made money of patents on the teepee (you know, the Stone Age tent) and the padlock --which has been found in six thousand year old archaeological digs. (As well as being so common in medieval garbage dumps as to be pretty much junk even to archaeologists.) You might almost think .. .  nah. 

 

So when Swan and Edison came to their agreement in 1883, it was just a bog-standard approach to doing business. If you wanted into the American market, you cut a deal with a local partner. The local partner might dig up an "inventor," or "invent" the process independently, Then they would come to an agreement under which the combined firm split up the lucrative American and English markets, with th rest of the world as the gravy on top.

 

So it is in the case of the American market. Swan, either the inventor of the lightbulb, or, more likely, the winner of the ongoing British patent battle, cut Edison in. Edison got to make lots of dough on the American market, Swan also got to make lots of money. Given that they both had to fight off patent interlopers, they developed a common interpretation of the history of the lightbulb. While this interpretation was incorrect as history of technology, it was court-enforceable. (And given all the money that was tied up in it, understandably so. Who wants a true history of technology when it means pensioners eating pet food because their GE share value has collapsed?) 

 

This makes Thomas Edison seem like a less-than-savoury figure, and, in a sense, this is true. But he was following on in an American tradition that goes back at least as far as Robert Fulford, and probably got himself to sleep at night by telling himself that if he wasn't doing it, someone else would. Where I do fault Edison, and think of this as something worth getting excited about, is that his publicity did a great deal to propagate the idea of innovation as being driven by a heroic inventor in his "research lab." This, in turn, provides a veneer of intellectual legitimacy to the often dishonest and rent-seeking practices of patent law.

 

Coming down to Elon Musk, we have the figure of an "inventor" who can only succeed if, basically, the Government builds him a Mars rocket and lets him rake off the profits. Which, absurd as it sounds, is how the transcontinental railways got built, so why not give it a whirl? 

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An interesting point has come up regarding the number of engines being used on this BFR--throttling.  The requirement to be able to land the booster and Mars vehicle imposes a size limitation on the engines, because even throttlable rocket engines have a minimum thrust setting.  Admittedly the booster configuration looks to be using only a small fraction of its engines for landing anyway, so in theory the others could be replaced by larger units.  But having two different engine models on the booster would increase complexity and probably would not be cost effective.

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Touche!  But of course Elon is trying to get Mars travel costs down by three orders of magnitude.  Indeed, SpaceX's real achievement so far is drastically reduced orbital launch costs; he is totally eating ULA's lunch in that respect, unscheduled disassemblies notwithstanding.

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Meanwhile, Blue Origin successfully tested its crew escape system today, recovering not only the capsule (which was obviously the main point) but also the booster, which guided itself to a successful landing.  The booster was not expected to survive the ejection intact, as it involved the explosive separation of the capsule at max-Q.

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Gaaaaaaaaah. Don't do that. Read up on the N1. Ganging many small motors is a complexity like n!. Small numbers of much larger engines, though it frontloads the engineering challenges into making those big motors, is the only real path.

 

People said that about the Falcon, when they announced an unprecedented 9 first stage engines, and some are still saying the same thing about the Falcon Heavy, which features 27 engines at launch. It turns out that engine development has come a long way since the 60's and a few of the old truisms no longer apply. For one thing, the Merlin engines, unlike the NK15, are covered in sensors linked up to fast computers. If something goes wrong (as has happened twice, I believe, once on the pad and once in flight) the engine automatically shuts down before an explosion can happen. And with 8 other engines available to take up the slack, the payload can still get to orbit even after an engine failure. 

 

Elon Musk's modus operandi is to take a fresh look at assumptions everyone just takes for granted, and finding a new approach. Mass producing the Merlin has not only made it cheaper, it's also allowed them to test it more thoroughly than most other rockets in history. Only a single Merlin engine has ever failed in-flight, despite nearly 300 having flown. Another one did fail during a test fire on the pad, at which point they shipped in a spare and launched successfully a week or two later. 

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  • 2 weeks later...

SpaceX has replicated the recent Falcon 9 failure on the pad, causing failure of a COPV* solely through the temperature and pressure of the helium loaded into it.  This can be corrected with a modification to the helium loading procedure, and SpaceX is hoping to resume launches before end of year.

 

 

* Composite Overwrapped Pressure Vessel - the helium tank that is used to maintain pressure inside the liquid oxygen tank.

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