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/sci/ - Science & Math

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5142067 No.5142067 [Reply] [Original]

Why aren't space ports built on top of very tall mountains or on towers on top of mountains to save fuel?

>> No.5142078

They wouldn't achieve a high enough velocity.

>> No.5142081

>>5142078
Right, because the air is thinner so the jets wouldn't get enough oxygen. My bad.

>> No.5142113

I don't know the answer to OPs question, except to guess that it's more to do with being in a convenient location relative to the space craft construction site and being at a latitude that sets you up for efficient entry to desirable orbit paths. And rockets don't need air, the fuel they consume includes whatever oxygen is required for them to burn. (That's why they can still work in space)
I actually think OP's question is interesting, but my guess is that it'd be more trouble then it's worth to build and launch rockets from the top of a mountain.

>> No.5142183

>>5142067
Logistic nightmare to maintain the facilities and transport people and equipment to them.
Also, weather plays a big role in launching stuff.

If you want to idealize the whole mess you'd also build an acceleration ramp up the side of the mountain instead of just launching from the top of it, that way your craft could launch from a few kms height with a high speed already and save a lot of fuel.

Now good luck convincing anyone to spend 25 billion USD on such a launch faciltiy.

>> No.5142273

>>5142183
Make me a multibillionaire and I'll do it for you.

Promise

>> No.5142290

The inconvenience of working on a mountain offsets the very minor gain you would get from the increased altitude.

As others said, weather is a major factor in launches... as well as the fact that we like to launch over the ocean.

Even the fact that the land in florida is extremely flat is a consideration... have you ever seen how they move rockets around? Imagine trying to roll those bitches at an incline.

>> No.5142291

>>5142290
To follow up with the weather thing... we launch in florida because it basically never goes below freezing temperatures there. On a mountain, you'd have shit freezing all the time.

Florida allows us to launch year round, no adjustments required.

>> No.5142311

Why do you guys answer questions you don't know anything about?

You would have negligible gains from launching on a mountaintop. Latitude, on the other hand, is very important. THAT is why we launch in Florida. That's why the Europeans launch from South America. The closer you are to the equator, the more the Earth's rotation gives you a boost.

>> No.5142320

It's better to start the rockets off near sea level, so it has more air to push against.

>> No.5142343

>>5142311
This is the only sane comment in this thread.

>> No.5142361

These places are chosen as much for having something big and empty to the east as for being equatorial.

>> No.5142383

Because moving shit you need for the launch up on mountains would be hard as fuck and waste more fuel than you save.

>> No.5142461
File: 249 KB, 1111x667, Pegasus rocket launch.jpg [View same] [iqdb] [saucenao] [google]
5142461

Gonna play devil's advocate here...
Yes, the potential-energy gains would be virtually nonexistent, but there are other gains to be had. Most notably, atmospheric pressure near sea level (during those first few thousand meters when oh-so-much propellant is consumed) significantly reduces the rocket's specific impulse and forces designers to compromise on first-stage nozzle size (therefore reducing efficiency at high altitudes as well). Launching from, say, 6000 m, would cut atmospheric pressure in half at launch, significantly improving launch efficiency and allowing designers to compromise less on nozzle design.

This isn't just theory, either; the air-launched Pegasus rocket takes advantage of this effect.

>> No.5142493

>>5142461
I guess it also takes advantage of the speed boost the jet provides. At equatorial surface you get 500m/s for free. A jet could quite easily add 200m/s to that.

>> No.5142504

>>5142493
Yes, that does help too. In fact, I sort of wonder if the jet's velocity helps MORE than the equatorial velocity, seeing how, with Pegasus, those first few seconds of burn are in the prograde direction, rather than perpendicular to it (up). I would think that would help, Oberth effect and all that.

>> No.5142639
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5142639

Are there any orbital rockets that cold-launch from a tube like some missiles do?

>> No.5142834

>>5142639
Yes. The navy shot down a satellite in 2008 with a missile like you describe.

>> No.5142838

why not shoot supplies into space from a giant cannon?

>> No.5142842

>>5142639
Yes, the Russians sometimes use old submarine based ICBMs to launch satellites:
http://en.wikipedia.org/wiki/Volna
http://en.wikipedia.org/wiki/Shtil%27

>>5142834
Those rockets aren't orbital they just have to hit it.

>> No.5142853

>>5142639
Yes, and all of them are converted Russian missiles: Shtil, Volna, Start-1, Strela, Rokot, and Dnepr. Clean designed rockets all launch from pads, which are much cheaper to build and maintain. For example, Orbital Science's Taurus and Minotaur rockets use converted Peacekeeper and Minuteman missiles for the first stages, but launch from above-ground pads.

>> No.5142946
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5142946

>>5142081 Right, because the air is thinner so the jets wouldn't get enough oxygen. My bad.

Are you serious?

>> No.5142960

Because the terrain isn't suitable for it. You'll have issues like glaciers, and excessive wind. The only way to effectively build one would involve leveling the peak of a mountain that's high enough to get beyond the cloud cover, and I just doubt that it will be worth the amount of expense to build one there as opposed to somewhere near sea level with relatively stable weather.

>> No.5143003

>>5142838
Cannons are expensive. If it blows up on one launch you lost your whole capital investment, which you needed to amortize over many launches. You still need a rocket on the projectile to circularize the orbit. You need a long barrel on the cannon to keep the accelerations down to the point that a rocket would survive, making the cannon even more expensive.

>> No.5143024

>>5143003
Oh, and by the way: people are planning to build them anyway. There's one company right now that's working on a system for launching hydrogen tanks into orbit from a cannon in the ocean, so they can sell it as rocket fuel for satellites and other spacecraft.

>> No.5143219

>>5143024
sauce? the only cannon launcher I'd heard of was by Bull, and he was assassinated for it.