Author Topic: Totally crazy idea: Space launch site on Mt Kilimanjaro?  (Read 56474 times)

Offline sghill

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #100 on: 06/15/2018 07:27 pm »
Let it burst through several bladders of reinforced cellophane or something similar.

Without doing the maths, my gut reaction is that the strength of the plastic, in order to hold the pressure difference (the weight of the air it is supporting), must be higher than the pressure difference itself. So hitting the "bladder" will always be worse than hitting the air itself.

Well, simple Seran wrap is 12.5 μm thick with a tensile strength of 1,000 to 12,000 per square inch! So if you are starting at 8 or 9 ambient PSI and dropping down to 1 or 2 PSI for the exit pressure, your tensile strength will determine how large a diameter you can make your plastic sheet before it bursts on the center. Assuming you make the tube a diameter small enough for only 1 PSI difference between each side of the sheet, only 9 sheets of Seran wrap between the top and bottom of the tube are needed to make the bottom pressure equal to the top pressure. Remember also that the air above each sheet is supported by the air below it. The sheet at the bottom doesn't support the whole air column.
« Last Edit: 06/15/2018 07:57 pm by sghill »
Bring the thunder!

Offline fiduce

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #101 on: 10/25/2020 12:59 pm »
What about a rail gun ? Giving the space ship as much vertical energy as possible BEFORE its lift off.
The stake is to lower the amount of "flying fuel".
Instead of igniting an engine at speed 0 and altitude 0, you would ignite an engine at Kilimanjaroo height, with a rail-gun speed of at least mach 1. The acceleration, from the valley to the top of the mountain, would be very acceptable by a human (less than 2 G).
You could even "open the flying path" with a suction made with the help of some high speed bullets shot from a secondary rain gun. Those bursts of reusable guided bullets would be shot from another much faster (but with a smaller section) rail gun (see the geography of the region) in order to cross the space rocket path, and to expand/airbrake in front of it. This would create some extra, and fuel free, suction to help the rocket lift off.
Each bullet would come back on its own after use (driving its descend to a choice between a set of landing zones, depending on the wind).
Security would be better with that initial speed: if the rocket engine doesn't start, you just have to separate the human cap, and make it land with parachutes.
You could launch one vehicle every day or even faster (depending on the time you need to full-fill the capacitors with solar power), and assemble their payload on low orbit, like a Lego construction. The need for embedded fuel would be minimal, but still very high (I must agree).
But I think that high frequency space launches can not be fuel-only (I know there is no fuel in a rocket ...) energized like today's monthly launches. We need a space elevator. A rail-gun space elevator.
The south west side of Mt Kilimanjaro looks appropriate for such a project. A 15-20 kilometers long rail-gun, ending in a vertical bend.

Make Space X and Hyperloop fusion.
« Last Edit: 10/25/2020 02:15 pm by fiduce »

Offline Twark_Main

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #102 on: 10/26/2020 01:47 am »
What about a rail gun ? Giving the space ship as much vertical energy as possible BEFORE its lift off.
The stake is to lower the amount of "flying fuel".
Instead of igniting an engine at speed 0 and altitude 0, you would ignite an engine at Kilimanjaroo height, with a rail-gun speed of at least mach 1. The acceleration, from the valley to the top of the mountain, would be very acceptable by a human (less than 2 G).
You could even "open the flying path" with a suction made with the help of some high speed bullets shot from a secondary rain gun. Those bursts of reusable guided bullets would be shot from another much faster (but with a smaller section) rail gun (see the geography of the region) in order to cross the space rocket path, and to expand/airbrake in front of it. This would create some extra, and fuel free, suction to help the rocket lift off.
Each bullet would come back on its own after use (driving its descend to a choice between a set of landing zones, depending on the wind).
Security would be better with that initial speed: if the rocket engine doesn't start, you just have to separate the human cap, and make it land with parachutes.
You could launch one vehicle every day or even faster (depending on the time you need to full-fill the capacitors with solar power), and assemble their payload on low orbit, like a Lego construction. The need for embedded fuel would be minimal, but still very high (I must agree).
But I think that high frequency space launches can not be fuel-only (I know there is no fuel in a rocket ...) energized like today's monthly launches. We need a space elevator. A rail-gun space elevator.
The south west side of Mt Kilimanjaro looks appropriate for such a project. A 15-20 kilometers long rail-gun, ending in a vertical bend.

Make Space X and Hyperloop fusion.

Welcome to the forum!

In my opinion this particular idea has limited practicability. In essence it's a very expensive launch pad, and in exchange the first stage only gets 10-20% smaller. Given the high costs and the small payoff, I don't think the trade works in its favor.
"The search for a universal design which suits all sites, people, and situations is obviously impossible. What is possible is well designed examples of the application of universal principles." ~~ David Holmgren

Offline RanulfC

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #103 on: 10/29/2020 01:36 pm »
What about a rail gun ? Giving the space ship as much vertical energy as possible BEFORE its lift off.
The stake is to lower the amount of "flying fuel".
Instead of igniting an engine at speed 0 and altitude 0, you would ignite an engine at Kilimanjaroo height, with a rail-gun speed of at least mach 1. The acceleration, from the valley to the top of the mountain, would be very acceptable by a human (less than 2 G).
You could even "open the flying path" with a suction made with the help of some high speed bullets shot from a secondary rain gun. Those bursts of reusable guided bullets would be shot from another much faster (but with a smaller section) rail gun (see the geography of the region) in order to cross the space rocket path, and to expand/airbrake in front of it. This would create some extra, and fuel free, suction to help the rocket lift off.
Each bullet would come back on its own after use (driving its descend to a choice between a set of landing zones, depending on the wind).
Security would be better with that initial speed: if the rocket engine doesn't start, you just have to separate the human cap, and make it land with parachutes.
You could launch one vehicle every day or even faster (depending on the time you need to full-fill the capacitors with solar power), and assemble their payload on low orbit, like a Lego construction. The need for embedded fuel would be minimal, but still very high (I must agree).
But I think that high frequency space launches can not be fuel-only (I know there is no fuel in a rocket ...) energized like today's monthly launches. We need a space elevator. A rail-gun space elevator.
The south west side of Mt Kilimanjaro looks appropriate for such a project. A 15-20 kilometers long rail-gun, ending in a vertical bend.

Make Space X and Hyperloop fusion.

Add lasers :)
See: https://luf.org/t/bifrost.php

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline Nilof

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #104 on: 10/29/2020 03:08 pm »
Rail/coil guns can be worth it (see startram) if they actually give 4km/s of delta v with some cheap compact way to give the second half of the delta-v, or ace an outright space cannon, and for those you can do active structures to make them pop all the way up into the stratosphere. If you just want to make a stage slightly smaller, adding a reusable first stage like SpaceX is easier and more versatile.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Pete

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #105 on: 10/29/2020 07:52 pm »
If you wanted to launch a *lot* of rockets, you could use the mountain to advantage.

Build them on the plains below. No altitude issues, not too bad logistics issues.

Then, once your rocket is fully constructed and ready to launch, load it on the crawler-transporter (likely a variant of railway, actually), and take it to the top, and launch. Nothing except maybe fueling up happens at attitude. 95% of your GSE is at the ground level, not at altitude.

Pro: every single launch benefits from altitude advantage. Utter absence of thunderstorms, and any real weather. There is almost always a stiff breeze, but very rarely strong wind. Precipitation is common but *very* minimal, as snow only. There are very rarely any significant high altitude winds, due to the utter absence of jet streams that near the equator.
Con: Initial build of the railway/crawlerway will be quite expensive. Some significant costs needed for the actual lift and transport of your rocket and its fuel up that mountain.
And , of course, the general disadvantage of having a launch site with a LOT of ground to the east, for your rocket to overfly.

You would need to want to launch a **lot** of rockets, of very similar size, to get the benefit from this sort of scheme. We are talking one per day or more sort of scales.

Something like SpaceX's reuseable first stages would do well here, as long as they all do RTLS flight profiles. (but returning to the assembly area, not to the peak)
« Last Edit: 10/29/2020 07:53 pm by Pete »

Offline TrevorMonty



If you wanted to launch a *lot* of rockets, you could use the mountain to advantage.

Build them on the plains below. No altitude issues, not too bad logistics issues.


This is Africa, logistics is always an issue.


Offline Paul451

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #107 on: 10/30/2020 10:36 am »
Replying to and riffing on various comments over the thread:

Assuming you can convince Tanzania to let you launch rockets off their world heritage listed mountain, you also need to convince Kenya to let you launch into their territory. Every reasonable flight path (north east, equatorial, low-inclination south-east) puts you over Kenya. That said, there's a bunch of national parks to launch over, helping avoid higher population areas.

Convincing Kenya might require putting the major manufacturing and admin site in Kenya, just over the border. Logically, near Voi. The integration and launch ops facilities would in Tanzania, just outside the Mt Kilimanjaro national park, with a dedicated rail line to the launch area at the base of the mountain.

Infrastructure:

Placing your major operations in Kenya helps with infrastructure, since Kenya is one of the more modern, prosperous and western-accessible African countries. (The flip-side of being more modern is it's going to be harder to convince them to get involved with something as weird as launching rockets off a mountain. As horrible as dictators are, "big men" are drawn to grandiose projects, and once you are in with the dictator, bureaucratic issues go away. Whereas more developed nations prefer sensible infrastructure projects, like road/rail/dams/ports.)

You've got port cities nearby, such as Mombasa. And Kenya has a standard-gauge rail-line between Mombasa and Nairobi, passing near the Tanzanian border, through Voi. There is also supposedly a still active British narrow-gauge line running across the Tanzanian border, from Voi to Arusha, wrapping south around the Mt Kilimanjaro national park, and branching south to the coast. It shouldn't be hard to convince the two nations to let you upgrade the line to standard gauge, with a dedicated branch-line from your ops centre to the base of the mountain.

First-stage recovery:

Given that there are national parks north and south-east, you can put your first-stage landing areas at the eastern edges of those parks, while avoiding most of the population. Nearby rail-links get you back to the manufacturing facility at Voi and/or the integration/launch facility near Arusha.

Launch:

People seem to be picturing two wildly divergent alternatives: evacuated mass-driver tubes running up the side of the mountain amd launching at near-orbital velocity; versus more conventional launchpads built on the top of the mountain.

But I think we can split the difference by using a rocket sled running up the side. The technology is much more mundane than a mass-driver, but gives more advantages than a static launchpad at the top.

The world land speed record is held by a rocket sled on a rail-line at Holloman USAF base; reaching over Mach 8 (nearly 3km/s.) The stack of solid rocket motors was several metres wide. Not far off the size of a conventional rocket stage. To actually release the launch vehicle, we need a rail-ejection system similarly to that used by  mobile platforms to launch large ICBMs since the beginning of the Cold War.

It should be technologically possible to build a rocket-sled track up the western side of Kilimanjaro (ideally, three or four lines optimised for different launch trajectories. NE/SE/Eq.) All the launch infrastructure (except the track) is at the base of the mountain. The distance up the side of the mountain (say 7km long to reach 5.5km ASL) would allow you to reach 2.5km/s at just 3.5g. IMO, that's too high a velocity at too low an altitude, so aim for a launch velocity of 1 to 1.5km/s.

[edit: Not even close. Not sure what I did there.]

After ejecting the launch-vehicle near the top of the track, the sled itself slams into a braking system for the last few hundred metres. (The empty (low mass) rocket-sled needs vastly less room to decelerate than it did to get up to speed.)

Assuming a two-stage launch vehicle, then after normal staging, fly the first-stage back to 200-250km down-range to land at the sites discussed above. No need to fly all the way back to the launch site.

It may not seem like much of a benefit (1km/s and 5km), but conventional launches use a disproportionate amount of fuel in the first part of the launch. Moving that mass to the rocket sled might let you increase the dry-mass ratio of the rocket itself to both increase payload capacity, and also widen the engineering margins. The latter lowering your manufacturing costs and increasing reusability (usual engineering rule-of-thumb is that halving the mass of a part increase costs and decreases lifespan both by an order of magnitude.) Softer margins can also let you down-shift materials; from composites to aluminium, aluminium to steel.
« Last Edit: 08/02/2021 05:10 am by Paul451 »

Offline davamanra

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #108 on: 08/02/2021 01:19 am »
Hey this idea worked on Fireball XL5, so if we can find long enough marionette strings let's give it a shot!

Just kidding and not poo-pooing your idea either.  There might be a way of using this idea for horizontal launch vehicles that would make them more viable.  This could save them a significant amount in fuel mass.  The launch vehicle could also use ramjets/scramjets and eliminate the need for turbojet propulsion, saving significant weight. 
Better to have more than you want than less than you need.
All's fair in love, war and engineering.

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