Every time I see something like a rocket or space shuttle launch, I can't help but wonder how much of the weight and cost could be saved using alternative methods. Even helium/hydrogen filled balloons could get them a good chunk of the way there. I know that would be horribly impractical for something the size of the shuttle and it's rocket boosters/fuel tanks, but if a balloon rig can get them to 120,000 ft they have gotten 15% of the way there (and overcome initial inertia) for pennys, and could probably shed a lot of weight that it normally uses to overcome those first 20 miles or so. Plus, at 120,000ft, gravity has already dropped from something like 9.8 newtons (sea level) to 9.68 (120,000ft). This might not seem like much, but it a good chunk of the way to the 9newtons that the Space Shuttle normally orbits at, and has to allow them to shed even more weight.
I'm obviously not an astro-physicist, physicist, or even that smart of a guy. I just can't help but think there are more efficient ways to get past 100,000ft without brute forcing the problem with rockets
The job of the rockets isn't to gain height (that is a side effect), unless you are working with a sub-orbital design. The job is to accelerate the payload to around Mach 25 or so. The reason this is challenging is that you not only have to accelerate the payload, you also have to accelerate the fuel, fuel tanks, engines, and other associated hardware too. Which is why the promising techs mostly revolve around using less fuel (such as rail launch for the initial oomph), or something like scram jet for the first stage (they part of the fuel and reaction mass comes from the atmosphere for the first few Mach). Or something that has very small fuel amounts, and only caries reaction mass (nuclear with H2O as the reaction mass).
I did the back-of-the envelope calculation a while ago, and if I recall, 5-10% of the energy used goes toward altitude, with the rest going towards horizontal velocity (modulo a bit of air resistance).
It's not that high. A lot of the losses in take-off aren't the consequence of drag. I think I saw on wikipedia that the aerodynamics losses are only 1-200 m/s of the delta-v budget.
Going by raw math, if the Earth were a perfect magic sphere with no atmosphere, you could attain "orbit" at ground-level by accelerating to 7.90 km/s. Then you could Hohmann to LEO with one 0.06 km/s burn to transfer up and another 0.06 km/s burn to achieve a circular orbit, so that's only 8.02 km/s in an ideal world. [Oh, I forgot that you start with about 0.40 km/s from rotation if you are near the equator.]
Oh, finally found a nice reference, on Wiki: http://en.wikipedia.org/wiki/Low_Earth_orbit#Human_useThe delta-v needed to achieve low earth orbit starts around 9.4km/s. Atmospheric and gravity drag associated with launch typically adds 1.5–2.0 km/s to the delta-v launch vehicle required to reach normal LEO orbital velocity of around 7.8 km/s (28,080 km/h). It doesn't break those out, unfortunately.
They aren't independent, though. "Gravity drag" comes from the fact that you need to put in 1G just to remain at constant speed. It's thus most efficient to have as high acceleration as possible. Unfortunately the aerodynamics work in the opposite direction: you don't want to go fast because that increases aero losses and there's a limit to how fast you can go in the lower atmosphere without breaking up. So the combined effects probably mean that the net loss is quite a bit larger than you could achieve if you only had to minimize one of them.
Actually, the job of the rocket is to to increase the potential energy of the payload, so using a He balloon to put some distance between the rocket/payload package and the ground is an entirely sensible proposition.
Most of what the rocket has to increase to take an object from the earth's surface to LEO. If you calculate the potential energy of a rocket in LEO and compare it to its kinetic energy, you'll find the latter is much larger. (I've already done this and posted it here.)
The higher you are, the greater your tangential velocity to the ground. Launching a rocket from the top of Mount Everest vs a beach on the Dead Sea is cheaper in terms of energy required to attain a given altitude.
This is almost nothing. The surface of the Earth spins at almost ~450 m/s near the equator and that's being some ~6300 km from the center. Climbing up another 10 km is not going to appreciably change your horizontal velocity.
You've lost me. Are you admitting that you have no counterargument to the video, which argues that space elevators are too impractical to be made in the forseeable future, or just pretending I didn't post it?
And by argument above, do you mean your paranoid rantings about government takeover of SpaceX? Personally, I'm more worried about corporations having too much influence on the government, not the other way around.
As for your nationalisation examples:
1. The gold confiscation had nothing to do with private companies
2. oil nationalisation didn't take place in America
3. I have no idea what in the 70's you're refering to
4. Bailouts: I'm going to go out on a limb and say that SpaceX will never be so integral to the national economy that it can't fail without taking down the whole system. Nor that Elon Musk will take on so much risk that he is in danger of failing.
And you can't have it both ways, Mr. "However, lazy quips aside, the past is not the future." If that's the position you're going to argue from, then you can defend literally any claim about the future, to the point where effects no longer have causes.
If you really want to learn about how moneyed interests have corrupted the US government, you should read _Republic, Lost_ by Lawrence Lessig http://www.indiebound.org/book/9780446576437
1 - gold confiscation illustrates the power of the political class over private interests in the US
2 - oil nationalisation illustrates the power of the political class over commercial interests globally
3 - Google is your friend
4 - The future size of SpaceX is mostly irrelevant as to whether they fall victim to the whim of a politician's nationalisation decree. The only excuse they need is SpaceX took the cheque and, after all, we know Musk didn't 'build it on his own'.
Your 'moneyed interests' point hints that you may be a partisan leftist? Since they are generally uninterested in discussing the facts we should probably stop here. If you are not a partisan leftist, I suggest you get up to speed on the abuse of political power in the West since FDR's Executive Order 6102.
So, dropped the space elevator subject? Did you watch the video? I'm still waiting for your explanation of how the video is wrong and space elevators are practical.
And no, I'm not a partisan anything. The disproportionate influence of those with power in the US is harmful to the interests of every part of the political spectrum, from left to right (including libertarians). With a government more beholden to the people than those in power we might not have better policies or politicians, but at least it would be 'our' fault. This the basic premise of the book I recommended. Which, by the way, was written by a former fan of Reagan and is non-partisan. Would you be so kind as to link me to specific information that you think is well researched and well written, as I have?
1. Oh, so you're saying that the banks were OK with the fact that Americans were still distrustful of them and keeping their money in gold rather than in banks?
2. Are you saying there's a global political class? Besides, the most recent (partial) nationalisation of an oil company (in Argentina) has what seems like the overwhelming support of the people.
3. You're really not giving me much to go on. All I have is "absurd nationalisations of the 1970s" which I'm now guessing refers to more stuff that happened in other countries, mostly not in "the West."
4. The size of SpaceX relative to our economy is relevant if you're trying to say the bank bailout of GM takeover is the precedent that the government will use. And the gov't didn't take a controlling stake in any of the bailed out banks. <s>But, as you say, the future is not the past, so why bother establishing precedent for something?</s>
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> after all, we know Musk didn't 'build it on his own'.
That you have never bothered to find out the context in which Obama said that is very telling. Here it is[0]:
> If you were successful, somebody along the line gave you some help.[1] There was a great teacher somewhere in your life. Somebody helped to create this unbelievable American system that we have that allowed you to thrive. Somebody invested in roads and bridges. If you’ve got a business. you didn’t build that. Somebody else made that happen. The Internet didn’t get invented on its own. Government research created the Internet so that all the companies could make money off the Internet.
So, in the sentences before what gets quoted, Obama is talking about "this unbelievable American system" that includes roads and bridges. And it's true that if you built a business, it's likely you did not build the roads or bridges we have today. So, isn't it reasonable to assume that Obama's 'that' referred to those same roads and bridges? Especially when his next point is that government research created the internet. If he really meant to say "you didn't build your business" wouldn't it have been a non-sequiter? And the gov't created the internet "so that all the companies could make money off the internet"
And you can't tell me that SpaceX, of all companies, hasn't benefitted from US infrastructure. They employ former gov't engineers, they transport their rockets between LA, Texas, Marshall Islands, and Florida using roads, bridges, and ports. Paypal wouldn't have existed without the internet. Even if Musk earned his money some other way, SpaceX uses the internet and its technologies extensively. I'm sure most of their employees went to public schools at some point. They're using NASA's launch facilities at Cape Canaveral.
> The point is, is that when we succeed, we succeed because of our individual initiative, but also because we do things together. There are some things, just like fighting fires, we don’t do on our own. I mean, imagine if everybody had their own fire service. That would be a hard way to organize fighting fires.
Pro tip: when someone says "the point is" what usually follows is their point. And in his main point, Obama acknowledges that success is partly due to intrinsic aspects of the individual. And he's not proposing that the government do everything, he's proposing that the government do things like provide fire fighting services[2]. The thing is, those still have to be paid for, which is why he gave that speech asking corporations to pay more taxes.[3]
[1] And there's no question that Elon Musk received help. One example: he was strapped for cash at one point recently and borrowed money from friends (had plenty of assets, not enough liquid assets)
[2] And even a libertarian would have to agree that the government should do that. Along with national defence, it is a public good http://en.wikipedia.org/wiki/Public_good
[3] Whether that is the best way to pay for things is a separate debate I'm not interested in having here.
Assuming the balloon itself has zero mass, every cubic meter of hydrogen in your balloon can lift a maximum 30 grams of payload. For the 2000 ton space shuttle, that's sixty million cubic meters - a spherical balloon half a kilometer in diameter. There's a reason we don't launch rockets with balloons.
I've seen this idea on Reddit before, and it was explained that the issue of getting to orbit has nothing to do with altitude and everything to do with velocity.
You can be a great deal farther away from the Earth than orbital altitudes, but if you're not actually orbiting, you're going to fall directly toward the surface.
This is not the disruption you're looking for. Every launch you're throwing away the entire machine. People keep coming up with the pithy 'imagine how expensive a transatlantic ticket would be if ditched the 747 into the sea at the end of every flight' but it's precisely true. Fuel costs hardly anything, the cost is of these fantastically advanced but single use machines.
So, make them properly reusable (not just rebuildable, not just reusable only say 5 times, able to turn around and fly again within a week) and you will change everything.
To my knowledge there's only sat launcher in the world that's working towards this, (the Skylon Space Plane) but that's probably 10 years and a few billion dollars away.
I don't know how reusable SpaceX's grasshopper efforts will be (as I intimated above there's reusable and then there's reusable). But I watch with fascination!
There are companies trying to do that as well. For instance http://en.wikipedia.org/wiki/Orbital_airship describes one where an airship that is part blimp, part fixed wing follows a trajectory where first it is lifted by being lighter than air, then it gets lift from moving fast through thin air, then it gets lift from being near orbital velocity.
Theoretically they should be able to get things in orbit very cheaply compared to rockets. So far those technologies have not worked in practice.
If we're working on the laws of physics, things like that win.
But in space launch, the laws of engineering have tended to be more important. A very reliable reusable rocket is probably going to be a better investment of the marginal dollar than any kind of air launch.
(Unless you are going all the way to things like Stratolaunch, which is riding SpaceX's rocket reliability. The mothership ought to be quite reusable, but building the biggest wing ever in history is going to be a tall engineering order. It remains to be seen which way wins out in the end.)
The ARCA team, one of the competitors in the Google Lunar X Prize, had the same idea. I'm not sure if they're following the same design now, or whether they changed it.
I don't know if balloons are practical, but that's the general idea of the Pegasus rocket, although it never achieved the cost savings they were hoping for.
My comment sparks a legitimate discussion, is on topic, and I get downvoted? My apologies for not knowing the finer points of why orbiting vehicles need to gain velocity instead of altitude...
I'm obviously not an astro-physicist, physicist, or even that smart of a guy. I just can't help but think there are more efficient ways to get past 100,000ft without brute forcing the problem with rockets