Author Topic: Totally crazy idea: Space launch site on Mt Kilimanjaro?  (Read 37508 times)

Offline aquanaut99

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OK, first of all, I know this is totally crazy and politically impossible (and the technical challenges would be daunting as well), but what level of performance improvement could be expected from current launch vehicles if they were launched from the summit of Mount Kilimanjaro in Africa?

IIRC, that was actually proposed by some SF writer (Clarke?) back in the 1950s.

Mount Kilimanjaro is almost on the equator (3 degrees South) and is 19'341 ft (5'895 m) high. Being a volcano, it also has a rather gentle slope which could make the construction of roads and tracks up to the summit possible, as well as a large caldera (several in fact) which could be paved for the launch platforms. And it is inactive.

What performance improvement would a Falcon 9, for example, have if launched from such a launch site, nearly 20'000 ft up?
« Last Edit: 02/21/2011 04:45 PM by aquanaut99 »

Offline TyMoore

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #1 on: 02/21/2011 05:46 PM »
Probably not enough to warrant the additional expense and complexity of building from scratch an entire launch complex and associated infrastructure at 19000 feet! Remember anything over 14000 feet, and people typically acclimated to sea level will need supplemental oxygen. Add to that the fact that most construction equipment isn't designed to operate at that altitude so things like diesel generators, excavators and dump trucks will need specially modified engine systems to be able to start at altitude. Add to that the necessary road construction project from a base camp. Probably a rail line from the coast. A port facility. A concrete plant nearby. Oh yeah, and naval security forces for expected merchant marine traffic that will of necessity pass nearby the Somali coast line.

And then there is the political situation in nearby Kenya, not as stable as it once was. No doubt certain 'gratuities' to certain officials may be needed to catalyze and maintain the whole effort.

And then there is the environmental red tape from building in a protected area in Tanzania.

And then there is the fact that there are glaciers and volcanic scoria that you are trying to build all this on...neither of which is very structurally stable: bed rock is only about five miles down, so pilings are probably are not an option either.

And then, if that wasn't enough, Kilimanjaro is still active. Not very active, but active is active in my book.

Billions and billions of $$$$

Still think it is worth the performance gains?
« Last Edit: 02/21/2011 06:00 PM by TyMoore »

Offline Lee Jay

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #2 on: 02/21/2011 06:15 PM »
What performance improvement would a Falcon 9, for example, have if launched from such a launch site, nearly 20'000 ft up?

Something like a few percent.

Offline aquanaut99

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #3 on: 02/21/2011 07:44 PM »
Still think it is worth the performance gains?

Thanks for your answer. No, I do not think it is worth it (and I didn't to begin with). I also know all about the technical and political problems, that's why I said it's a crazy idea. I was just wondering.

Offline malenfant

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #4 on: 02/21/2011 08:35 PM »
If politics were no issue then somewhere on the Somali coast would probably make more sense.  Watch out for space pirates though.

Offline extide

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #5 on: 02/21/2011 09:30 PM »
Most of the fuel used to get to orbit isnt used to go UP but to increase the velocity in the orbital direction. Remember, for example, ISS travels at ~17,500 mph, and you still need to get going that fast in the horizontal direction regardless of how high up you launch from. There will be a bit of a boost because of the increased radius of the earth at that point but that alone would probably be less than one percent.

Offline gospacex

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #6 on: 02/22/2011 02:14 AM »
Most of the fuel used to get to orbit isnt used to go UP but to increase the velocity in the orbital direction.

Most people on the forum know this already. 5km+ altitude does provide advantages of lower pressure - this allows more efficient nozzles on 1st stage.

The biggest problem with this proposal is that Tanzania is not Germany :) Doing business in 3rd world countries is PITA even at the sea level.

Offline Stephan

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #7 on: 02/22/2011 08:42 AM »
And DeltaV penalty due to atmospheric drag is marginal compared to gravitational losses.
Best regards, Stephan

Offline suncity

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #8 on: 02/22/2011 01:18 PM »
I think it would be interesting to have a numerical answer to this question, both for fun and to get a better perspective on the factors involved in launches. Without forgetting of course that Africa would be a challenging base of operations...

My 2 cents:

- the altitude of 5895 mt is equivalent (I think) to a delta V of 340 m/s, which is about 4,4% of orbital velocity

- Being at 3° from the Equator compared to 28° of KSC shoud add 56 m/s to the initial velocity, an additional 0,7% of orbital velocity

- I don't know how to quickly compute the effect of improved ISP from launching at altitude; but considering that atmosferic pressure is about 1/2 at that altitude and that ISp improves with altitude it should be possible to get an estimate of performance improvement. As an exemple, SSME ISP changes from 363 sec at sea level to 452 sec in vacuum (according to Wikipedia).
This improvement exists with unmodified engines, but would be even larger with a noozle extension optimized for starting the engine at 1/2 of sea level pressure.   

 
« Last Edit: 02/22/2011 02:21 PM by suncity »

Offline Wayne Hale

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #9 on: 02/23/2011 01:47 PM »
There is a common misconception that launching from a high place is important.  If you look at the amount of energy required (kinetic and potential) to achieve earth orbit, the kinetic part far outweighs the potential -- in other words it is more important to have speed than altitude by an order of magnitude.  High altitude launch sites have severe logistical problems (as noted by earlier comments).  So it is unlikely that launching from high mountain tops will ever realistically be practiced.  However, launching from locations near the equator have some advantages; the Ariane launch site in Guyana is a good example; as it the Kwajelein launch site originally used by SpaceX.  However, remote sites (like Kwaj) also have severe logistical problems which can reduce their effectiveness.  And for planetary missions or high inclination missions (as to the ISS), being near the equator has no advantage.  As it turns out the best launch sites have great logistical advantages - like KSC where there are long runways, rail access, great highways, and oceangoing barge access.

Offline madscientist197

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #10 on: 02/24/2011 07:39 AM »
TBH I find the idea of desecrating Kilimanjaro like this quite offensive. You end up with an obscene amount of irreversible environmental damage for very little gain.
John

Online hkultala

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #11 on: 12/19/2014 08:15 AM »
One thing neglected in most of the answers is the ability to use bigger nozzle.

The air pressure is so low(half of sea level) in kilimanjaro that bigger nozzle could be used.

This would easily increase the isp(and thrust) of the first stage by some 2-5%, though it would also increase the weight of the engines, and this would not work with falcon 9 because there would not be physical space for the nozzles.

But for example Delta IV or Angara which have only one single-chamber engine per core could use much bigger nozzle.

How much more would RS-68 weight if going from expansion ratio of 1:21 to something like 1:40 ?
Or how much more would RD-191 weight of going from expansion ratio 1:37 to something like 1:60 ?
And how much would the isp increase be in these cases?
« Last Edit: 12/19/2014 08:38 AM by hkultala »

Offline pagheca

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #12 on: 12/19/2014 08:24 AM »
Just a question: isn't launching from the bottom of a caldera potentially dangerous because of noise resonance (echo)?

I seem to remember this was a major issue for selecting Vandenberg or some other launch site in the past. Is it still an issue or not?

Online hkultala

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #13 on: 12/19/2014 08:27 AM »
Most of the fuel used to get to orbit isnt used to go UP but to increase the velocity in the orbital direction. Remember, for example, ISS travels at ~17,500 mph, and you still need to get going that fast in the horizontal direction regardless of how high up you launch from. There will be a bit of a boost because of the increased radius of the earth at that point but that alone would probably be less than one percent.

But when you start from higher, you can start going horizontally earlier.

The first kilometers after liftoff are the most expensive ones. Cannot go fast due aerodynamic drag, have to rise above the dense atmosphere as quickly as possible.

When launched form higher, athmospheric drag will be much lower and gravity turn can be started earlier. Savings on both atmospheric and gravity losses.

And then the effect of ability to use better nozzles.

The "increased radius of the earth" effect is in the class of 0.02 %, so totally insignificant.

Offline john smith 19

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #14 on: 12/19/2014 01:14 PM »
OK I'll bite.

The rough rule of thumb is atmospheric pressure at 5600m is 1/2 that at SL and nozzles can expand down to 40% of ambient before flow separation effects become severe.

Likewise an equatorial launch site buys you about 340m/s.

So you can slap a much bigger nozzle on the engines (pretty much the default move when management calls for more Isp) and you get higher starting velocity launching East than at around 28deg of US launch sites. It's close to Mach 1, which is still only 1/23 of orbital velocity (neglecting any losses) but not to be sniffed at if you have to get it by burning propellant.

But $deity what a PITA  :(. There's a pretty major tourist business that's going to take a beating. I'm guessing the local tribal elders will be more than a bit miffed and the hardware is coming several 1000 more Km's to get there.

If you want performance at any price then Somali is the choice geography wise in Africa.

BTW It's not often realized that the Italians launched a few Scout solids off the African coasts in the 1960's. It's near "Malindi" in Kenya.

http://en.wikipedia.org/wiki/Broglio_Space_Centre

TBF In terms of up and running site Kourou has a lot going for it. 
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Offline Danderman

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #15 on: 12/19/2014 02:02 PM »
We need Mike Heney to tell us about a better site in South America.

Offline Proponent

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #16 on: 12/19/2014 02:36 PM »
OTRAG launched a few rockets in the 1970s from the Congo, though it never achieved its orbital ambitions.  I imagine that the very low-tech nature of OTRAG's rockets meant that it was relatively insensitive to the quantity and quality of the available infrastructure.

Offline dchill

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #17 on: 12/19/2014 04:30 PM »
We need Mike Heney to tell us about a better site in South America.

Do you mean this inactive volcano peak in Equador?
"The highest mountain on earth is Mt. Everest in Nepal at 29,029 feet above sea level. However, it not the point on earth that is farthest from the center of the planet. That honor belongs to the volcano called Chimborazo in Ecuador."
<<http://en.wikipedia.org/wiki/Chimborazo>>

Obviously there would be logistical issues.

Offline fast

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #18 on: 12/19/2014 05:07 PM »
Must be the best place on earth for SSTO launch :)

Offline R7

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #19 on: 12/19/2014 05:28 PM »
Must be the best place on earth for SSTO launch :)

The NE/E/SE neighboring countries might not like the risk from those launches at all. Plus all the prementioned reasons.
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Offline DMeader

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #20 on: 12/19/2014 07:13 PM »
This reminds me of a segment in "The Moon Is A Harsh Mistress". Manny and the Professor visit earth, and on their tour tell every country they visit how this or that mountain or volcano or piece of high terrain is the perfect site for an earth-based escape-speed induction catapult, to reduce the cost of sending payload to the moon. Yep, Kilimanjaro was mentioned as a possible candidate.

Maybe we should think about that? (ducks... no, I am not taking this at all seriously...)
« Last Edit: 12/19/2014 07:14 PM by DMeader »

Offline mheney

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #21 on: 12/19/2014 08:21 PM »
We need Mike Heney to tell us about a better site in South America.

Yeah, I actually talked with the government in Ecuador about high-altitude launch sites back in
the late '90s.  Had we been able to put together about $250M in investment money, we might
have made a go of it ...

Offline pericynthion

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #22 on: 12/19/2014 10:05 PM »
A launch "blowpipe" built under Kilimanjaro is also featured in Alastair Reynolds' excellent novel "Blue Remembered Earth".

Offline llanitedave

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #23 on: 12/20/2014 01:55 AM »
TBH I find the idea of desecrating Kilimanjaro like this quite offensive. You end up with an obscene amount of irreversible environmental damage for very little gain.

It's not irreversible.  The next eruption is going to wipe the whole thing clean.

(I love a good thread necro!)
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Online Eerie

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #24 on: 12/20/2014 09:47 AM »
If we use a mountain anyway, why not build an electromagnetic mass driver into the slope? The volcano will provide geothermal power. :-)

Offline DMeader

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #25 on: 12/20/2014 01:23 PM »
If we use a mountain anyway, why not build an electromagnetic mass driver into the slope? The volcano will provide geothermal power. :-)

Heinlein already thought of that. See my post up the thread a bit  :)

Offline R7

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #26 on: 12/20/2014 02:38 PM »
If we use a mountain anyway, why not build an electromagnetic mass driver into the slope? The volcano will provide geothermal power. :-)

*stabs EM mass driver on mountain slope in the heart*

*checks for movement*

*stabs it once more just to be sure*

Now stay dead!  ;)
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Offline pagheca

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #27 on: 12/20/2014 02:41 PM »
If we use a mountain anyway, why not build an electromagnetic mass driver into the slope? The volcano will provide geothermal power. :-)

Than why don't we get a step further and use lava like at the end of "Journey to the Center of the Earth", to give the rocket a starting kick?

As llanitedave pointed out you get a free-bonus after each launch: automated summit cleanup.
« Last Edit: 12/20/2014 02:42 PM by pagheca »

Offline fast

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #28 on: 12/20/2014 03:11 PM »
Must be the best place on earth for SSTO launch :)

The NE/E/SE neighboring countries might not like the risk from those launches at all. Plus all the prementioned reasons.

SSTO rockets arent any riskier than any other space LV. But must require less infrastructure, something similar to small airport - few hangars, fuel deport, etc.

Offline R7

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #29 on: 12/20/2014 03:48 PM »
SSTO rockets arent any riskier than any other space LV. But must require less infrastructure, something similar to small airport - few hangars, fuel deport, etc.

They aren't much less riskier either.

You've been watching too much Skylon videos.
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Offline fast

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #30 on: 12/20/2014 07:09 PM »
SSTO rockets arent any riskier than any other space LV. But must require less infrastructure, something similar to small airport - few hangars, fuel deport, etc.

They aren't much less riskier either.

You've been watching too much Skylon videos.

I was actually about VTOL SSTO. Kind of F9R first stage. All you need is small takeoff-landing concrete field (about the size of floating spaceport-drone:) ).

PS I suppose there will be no benefit for Skylon. If it will be able to takeoff from such altitude at all.
« Last Edit: 12/21/2014 07:49 AM by fast »

Offline R7

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #31 on: 12/21/2014 09:22 AM »
I was actually about VTOL SSTO. Kind of F9R first stage. All you need is small takeoff-landing concrete field (about the size of floating spaceport-drone:) ).

PS I suppose there will be no benefit for Skylon. If it will be able to takeoff from such altitude at all.

Thinner atmosphere is a negative in landing, needs more dv to kill higher terminal speed. IMHO a spaceport-drone would make more sense than ruining some mountain slope. Airbreathing VTOL launch assist platform.

And you are right about Skylon, its T/O speed is supposed to be very high (~ Mach 0.5!) even at sea level. Maybe a free initial acceleration by sending it downhill? (JK)
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Offline john smith 19

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #32 on: 12/21/2014 09:55 AM »
SSTO rockets arent any riskier than any other space LV. But must require less infrastructure, something similar to small airport - few hangars, fuel deport, etc.
Vertical takeoff SSTO's have 2 risks.
If the design goes slightly overweight or the engines slightly underperform it does not take off at all

The other fact is simply that SSTO's expect to lose 1/3 to 2/3 of the payload of a TSTO.
Quote
They aren't much less riskier either.

You've been watching too much Skylon videos.
Actually Skylon is the odd one out in being much less riskier than VTOL SSTO's.

All aircraft and LV's have a "black zone" when engine failure will crash the vehicle, but an SSTO will have a longer period of that because it has no lift.

Skylon's winged lift uses 1/3 the thrust of its GTOW. If it's engines underperform or its structure is too heavy it still flies.

None of which is really relevant to where that runway is. 
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Offline fast

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #33 on: 12/21/2014 03:59 PM »
dear JS19,

- how does risk of  "If the design goes slightly overweight or the engines slightly underperform it does not take off at all" applicable to VTOL SSTO more than to ANY other LV or even aircraft?
And after all if VTOL device dont take off the ground there no risk at all or very low :)

- why "The other fact is simply that SSTO's expect to lose 1/3 to 2/3 of the payload of a TSTO" is a risk?
Today we have a range of expendable LV with different performance, from very good payload fraction of 4-5%, to quite poor of around 1%. Somehow no one saying that those LV with low payload fraction a risky...

 

Offline Avron

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #34 on: 12/21/2014 04:08 PM »
If we use a mountain anyway, why not build an electromagnetic mass driver into the slope? The volcano will provide geothermal power. :-)

*stabs EM mass driver on mountain slope in the heart*

*checks for movement*

*stabs it once more just to be sure*

Now stay dead!  ;)

At 10Kft in altitude, everyone is dying from lack of oxygen.. just give it a chance it will die 

Offline fast

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #35 on: 12/21/2014 04:16 PM »
Something like SERV (https://falsesteps.wordpress.com/2012/08/18/servmurp-chryslers-space-truck/) worth to try from >6000m mountain near equator.
Changes I would suggest is: remove jet engines and aerospike, only rocket power for takeoff ad landing.
Maybe methane instead of LH for smaller LV.

45% atmospheric pressure allow to use near vacuum optimized nozzle witch will produce high specific impulse right from take off, significantly reduced atmospheric drag and a little less gravitational drag.
All this make mountain top makes VTOL SSTO more viable increasing its payload fraction. 

Offline llanitedave

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #36 on: 12/21/2014 07:07 PM »
If we use a mountain anyway, why not build an electromagnetic mass driver into the slope? The volcano will provide geothermal power. :-)

*stabs EM mass driver on mountain slope in the heart*

*checks for movement*

*stabs it once more just to be sure*

Now stay dead!  ;)

At 10Kft in altitude, everyone is dying from lack of oxygen.. just give it a chance it will die

10,000 feet?  Nothing.  Tibetans and some Peruvians live at that altitude full time.  Most people can acclimate.

At 19,000 feet, now that's another story.
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Offline RobLynn

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #37 on: 12/22/2014 01:12 PM »
Individuals have lived at 5950m (19500ft) for 2 years continuous http://www.ncbi.nlm.nih.gov/pubmed/12631426, and there is a Peruvian town of 7000 people at 5100m (16500ft), same as Everest base camp where normal westerners hang out for months at a time.  You can be active at such altitudes without too many problems, though acclimatising takes 1-2 weeks.  Having a bit more oxygen pumped into your buildings makes it a lot more comfortable.

Launching from altitude will typically cause a re-optimisation of initial acceleration to higher values that reduce gravity losses, as well as lowered aero losses for overall greater deltaV savings.  It may also allow a more squat vehicle with reduced thermal protection area, lower re-entry peak temps/accelerations and reduced structural/hydrostatic pressure overheads and lighter aeroshells.

Chimborazo at 6250m and 1° from equator in Ecuador is probably best (If it was politically sound).  And a funicular railway launch platform/tower could crawl up its side (or use a large cable car) from surrounding highlands at 3500-4000m to make life a bit easier.

Could be worth it for a return to launch site reusable TSTO like space X to squeeze the last few percent in cost or payload capacity out of the system in a highly competitive market, but as many have noted it makes most sense for SSTO where payload fractions are small and small gains in Isp, dry mass and deltaV reduction can have bigger impact.

A falling counterweight driven accelerating funicular/cablecar to raise lift off velocity to 50-100m/s would be a cheapish augmentation to save a bit more delta V.
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Offline pagheca

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #38 on: 12/22/2014 02:02 PM »
Individuals have lived at 5950m (19500ft) for 2 years continuous http://www.ncbi.nlm.nih.gov/pubmed/12631426, and there is a Peruvian town of 7000 people at 5100m (16500ft), same as Everest base camp where normal westerners hang out for months at a time.  You can be active at such altitudes without too many problems, though acclimatising takes 1-2 weeks.  Having a bit more oxygen pumped into your buildings makes it a lot more comfortable.

I've been working for some periods at more than 5,000 m (with long periods of acclimatization at 3000) and I ensure you it is really demanding for an healthy westerner, specially if you have to spend the night there. Also, remember you wouldn't be selecting personnel among mountaineers or natives but among extremely good engineers and technician coming from any region of the US, etc.

So, "without too many problem" is really overstating, trust me... Not mentioning 7,000. At that altitude the risk of emphysema is large. O2 bottles and oxygen enriched environments still help but as soon as you work outdoor your brain becomes quite unreliable. I can't really see such a highly demanding business to be operated there.
« Last Edit: 12/22/2014 02:03 PM by pagheca »

Offline RobLynn

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #39 on: 12/22/2014 02:11 PM »
Paper on launching from towers:http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20030022661.pdf

Suggests 4.7% gain in average Isp and about 50 m/s saving in delta V for 5km altitude launch ( LH2/LOX engine) vs sea level launch.

Assume a  sea level launch SSTO with RD180 engine having 330s average Isp and 9100m/s delta V (lower gravity losses of dense fuel), it will deliver 6.0% of lift off mass into orbit.

With 4.7% Isp boost and 50m/s deltaV reduction get 345.5s average Isp and 9050m/s delta V for 6.9% of lift off mass into orbit.

That is a pretty massive gain for an SSTO, equivalent to almost 450m/s saving in deltaV at the average Isp of the sea level optimised rocket, and could mean doubling the payload.
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Offline RobLynn

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #40 on: 12/22/2014 03:08 PM »
I've been working for some periods at more than 5,000 m (with long periods of acclimatization at 3000) and I ensure you it is really demanding for an healthy westerner, specially if you have to spend the night there. Also, remember you wouldn't be selecting personnel among mountaineers or natives but among extremely good engineers and technician coming from any region of the US, etc.

So, "without too many problem" is really overstating, trust me... Not mentioning 7,000. At that altitude the risk of emphysema is large. O2 bottles and oxygen enriched environments still help but as soon as you work outdoor your brain becomes quite unreliable. I can't really see such a highly demanding business to be operated there.

(Note that was 7000 people living in a town at 5100m, not people living at 7000m).

I've spent several days above 5000m, and climbed to 5600m, and like the 10's of thousands of other westerners who have been to Everest I did not find it that difficult (even though I'm a big tall unfit guy with abnormally small lungs).  Not everyone acclimatised in the time they had available, but most managed.  I also saw oxygen available on the trains that go from China to Lhasa over a 5100m pass, but I didn't see anyone bother with it.  Seeing Crows flying around was amazing.

It may not be sensible to set up a whole complex launch facility at >4500m, unless the workers used supplementary oxygen some or all of the time (which wouldn't be much different from carrying a toolbelt or wearing other safety gear), and not life threatening if you ran out - just more tiring.   But with a well established technological facility you could have oxygen enriched buildings and hyperbaric facilities for gradual acclimatisation even for short term visitors.

It is not hard to find locals in any of these high-altitude locales who can work happily at >5000m (there have been mines at 5350m), as can many westerners given time.  But moving a LV 1-2000m up a mountainside to be launched after it is prepared for launch might be easier.
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Offline pagheca

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #41 on: 12/22/2014 03:18 PM »
Look, Roblynn: congratulations for climbing so high (I'm honest, I like it too!).

I do not want to start an endless race to who got the longest one... :). So, if you think that, fine. However, "without too many problems" is IMHO stretching a bit the reality. Specially when you need to convey there thousands of highly qualified workers and you have no room for errors. And we can have fun with this (and other) "totally crazy" ideas, until we do not want to demonstrate they are serious.

The observatory I was working with, ALMA, until a few months ago, forbidden to sleep in the facility overnight. We had one of the most powerful supercomputer of the world there, and it was ok to stay there during the day. However, we got a quite high number of fatalities due to people accidents during construction because of stupid behaviours due to high-altitude sickness. We had to establish very hard rules for workers, including stiff driving rules. And still, 99% of the high-tech work was done (on purpose) at 3000.
« Last Edit: 12/22/2014 03:24 PM by pagheca »

Offline Prober

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #42 on: 12/22/2014 03:30 PM »
OK, first of all, I know this is totally crazy and politically impossible (and the technical challenges would be daunting as well), but what level of performance improvement could be expected from current launch vehicles if they were launched from the summit of Mount Kilimanjaro in Africa?

IIRC, that was actually proposed by some SF writer (Clarke?) back in the 1950s.

Mount Kilimanjaro is almost on the equator (3 degrees South) and is 19'341 ft (5'895 m) high. Being a volcano, it also has a rather gentle slope which could make the construction of roads and tracks up to the summit possible, as well as a large caldera (several in fact) which could be paved for the launch platforms. And it is inactive.

What performance improvement would a Falcon 9, for example, have if launched from such a launch site, nearly 20'000 ft up?

1/2 good idea....not a launch site.  A space elevator build site  :D

a whole different game.

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Offline RanulfC

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #43 on: 12/22/2014 08:40 PM »
If we use a mountain anyway, why not build an electromagnetic mass driver into the slope? The volcano will provide geothermal power. :-)

*stabs EM mass driver on mountain slope in the heart*

*checks for movement*

*stabs it once more just to be sure*

Now stay dead!  ;)

No, no you got the order wrong... It's "put the EM mass driver in the HEART of the mountain..." and an array of lasers around the rim... Sorry TMP flashback :)

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Offline RobLynn

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #44 on: 12/23/2014 07:57 AM »
The observatory I was working with, ALMA, until a few months ago, forbidden to sleep in the facility overnight. We had one of the most powerful supercomputer of the world there, and it was ok to stay there during the day. However, we got a quite high number of fatalities due to people accidents during construction because of stupid behaviours due to high-altitude sickness. We had to establish very hard rules for workers, including stiff driving rules. And still, 99% of the high-tech work was done (on purpose) at 3000.

How much of the death/accident rate would be down to cultural differences?  There is a huge difference between the West and the rest of the world.  I have spent several years working in China and am frequently amazed at just how careless the workers are about safety - and not because they need to be (eg won't use safety equip provided), but because their culture doesn't put any emphasis on safety, as evidenced by the suicidally aggressive/stupid manner in which they drive.

Do you know if the astronomy community looked into supplying workers with oxygen through a nasal canula?  A 2-5L 200 bar tank or a 1L LOX dewar should be enough for 8hours work.  Small enough to not be particularly annoying or inconvenient.
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Offline Tass

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #45 on: 12/23/2014 10:02 AM »
The observatory I was working with, ALMA, until a few months ago, forbidden to sleep in the facility overnight. We had one of the most powerful supercomputer of the world there, and it was ok to stay there during the day. However, we got a quite high number of fatalities due to people accidents during construction because of stupid behaviours due to high-altitude sickness. We had to establish very hard rules for workers, including stiff driving rules. And still, 99% of the high-tech work was done (on purpose) at 3000.


Offline pagheca

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #46 on: 12/25/2014 09:47 PM »
RobLynn: Everyone going up to the site must bring O2 bottles with him. However, people usually don't use them as it's very dry and therefore quite annoying in the nostril for long time. I, for one, used it only once while doing a survey on rough terrain at ~ 5,600 m (in winter).

Thanks for the cartoon, Tass. However, LACK and EXCESS of O2 have completely different effects... Xkcd quite wrong on this account :)
« Last Edit: 12/26/2014 10:26 AM by pagheca »

Offline cordwainer

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #47 on: 12/28/2014 03:40 AM »
Building a site on Mauna Kea and Haleakala would make more sense that Kilimanjaro for Space Launch. Stable American government, possible joint interest with Canada and Asia's space programs and it would create jobs for the locals. Of course getting stuff there would be a  B!?%#.

Offline Stormbringer

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #48 on: 12/28/2014 08:53 AM »
The local indigenous population probably would not allow something like that. They barely let the telescopes be built on their sacred mountains.
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Offline pagheca

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #49 on: 12/28/2014 09:31 AM »
The local indigenous population probably would not allow something like that. They barely let the telescopes be built on their sacred mountains.

Right, but this apply to ANY high mountain on Earth, specially isolated ones, and I'm sure Kilimanjaro is sacred to some local indigenous population too (not checked over the internet...).

However, we are talking about a "crazy" idea, and so we should not get too confident and realistic about them...
« Last Edit: 12/28/2014 09:33 AM by pagheca »

Offline llanitedave

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #50 on: 12/28/2014 03:45 PM »
Right.  The idea that it's "crazy" is what makes it fun to play with.  There's no danger of it actually happening, so you can easily explore potential implications in any direction you like.
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Offline Hop_David

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #51 on: 12/28/2014 11:54 PM »
If we use a mountain anyway, why not build an electromagnetic mass driver into the slope? The volcano will provide geothermal power. :-)

That was one of my daydreams, a west to east maglev rail up Chimborazo. I attempted to do some numbers:



Even at Chimborazo's altitude of 6 km/s, the atmosphere is still fairly dense. I believe .5 km/s may be somewhat higher than practical.

The equator's moving about .47 km/s. So .36 km/s with regard to earth's surface is .83 km/s.  I believe density at 18 km altitude is about about 1/10 that of sea level. Besides lower density, it's about 1/5 of the way towards the altitude where the air is rarefied enough to achieve orbital velocity.

I don't think that's enough to enable a SSTO. It might be helpful for a reusable booster that would land downrange from Chimborazo, somewhere in South America.

A booster starting it's burn at 18 km altitude and a horizontal velocity of .83 km/s has  some advantage over a regular booster. Is it worth building a major power plant and a maglev through ~100 kilometers of difficult terrain? Probably not.
« Last Edit: 12/28/2014 11:59 PM by Hop_David »

Offline Vultur

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #52 on: 12/29/2014 02:25 AM »
Why the limitation to 0.5 km/s? Erosion of the rails like the Navy railgun project has run into?


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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #53 on: 12/29/2014 01:39 PM »
Why the limitation to 0.5 km/s?

It's not good to travel at high speeds through a thick atmosphere. It causes excessive heating and drag. This is why rockets typically do a vertical ascent before they turn sideways for the major horizontal burn to achieve orbital speed.

Concorde would go mach 2 (about .68 km/s) at 18 km altitude. Even at this altitude it'd get pretty hot. At 6 km mountaintops, air density would be roughly triple that of 18 km altitude.
« Last Edit: 12/29/2014 02:14 PM by Hop_David »

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #54 on: 12/29/2014 03:19 PM »
Thanks for the cartoon, Tass. However, LACK and EXCESS of O2 have completely different effects... Xkcd quite wrong on this account :)

What exactly do you think Xkcd got wrong?  Xkcd seems to depict euphoric behavior, which is absolutely correct for hypoxia.

Offline Vultur

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #55 on: 12/29/2014 05:35 PM »
Why the limitation to 0.5 km/s?

It's not good to travel at high speeds through a thick atmosphere. It causes excessive heating and drag. This is why rockets typically do a vertical ascent before they turn sideways for the major horizontal burn to achieve orbital speed.

Concorde would go mach 2 (about .68 km/s) at 18 km altitude. Even at this altitude it'd get pretty hot. At 6 km mountaintops, air density would be roughly triple that of 18 km altitude.

Concorde didn't have a heat shield though, did it? Couldn't you carry a heat shield that was jettisoned once it got into thin atmosphere?

Offline indaco1

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #56 on: 12/30/2014 06:49 AM »
It's not good to travel at high speeds through a thick atmosphere. It causes excessive heating and drag. This is why rockets typically do a vertical ascent before they turn sideways for the major horizontal burn to achieve orbital speed.

I think it's also to minimize gravity losses.
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Offline R7

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #57 on: 12/30/2014 11:18 AM »
A booster starting it's burn at 18 km altitude and a horizontal velocity of .83 km/s has  some advantage over a regular booster.

There's also disadvantage; it has to start with very large AoA while surviving ~8 kPa dynamic pressure or have wings.
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Offline JasonAW3

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #58 on: 12/30/2014 02:11 PM »
Too bad we can't build an angled launch platform, effectively zero out the mass of a launch payload and launcher, let Earth's centripedial force fling the pacage upwards and gradually bring the effective mass back to normal to achievel orbit either around Earth or towards another planet.  Maybe the Alcubierre drive could achieve this from ground level?  Be kind of interesting to see what happens if it were activated in a gravity well anyway...
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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #59 on: 12/30/2014 03:07 PM »
A booster starting it's burn at 18 km altitude and a horizontal velocity of .83 km/s has  some advantage over a regular booster.

There's also disadvantage; it has to start with very large AoA while surviving ~8 kPa dynamic pressure or have wings.

Is that technically correct? I'm thinking that if the engines were positioned of struts at the nose or as far back as the center of mass and pointed where they needed to be pointed, the rest of the vehicle could just hang at whatever angle minimized those dynamic pressures.
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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #60 on: 12/30/2014 08:40 PM »
A booster starting it's burn at 18 km altitude and a horizontal velocity of .83 km/s has  some advantage over a regular booster.

There's also disadvantage; it has to start with very large AoA while surviving ~8 kPa dynamic pressure or have wings.

AoA?

How is the 8 kPa dynamic pressure arrived at? I'd like to include the equations in my spreadsheet if possible.

The 8 kPa dynamic pressure would decelerate the vehicle, correct? I am thinking the .36 km/s I have at the top is optimistic.

« Last Edit: 12/30/2014 08:41 PM by Hop_David »

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #61 on: 12/30/2014 10:02 PM »
R7 might be referring to the atmospheric pressure of 8kPa at 18km altitude.
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Offline R7

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #62 on: 12/31/2014 09:01 AM »
AoA?

Angle of attack. If the vehicle has traditional rocket shape, pointy end forward, slim body and engines in the aft it must point the nose up and initially fly "sideways" to counter gravity and rise. That's tough on the structure.

Alternatively you can have weird engine placements like Alf mentioned, either near the center of gravity or otherwise evenly distributed (both aft and nose) but that brings up challenging structure load paths too plus potentially issues with plume hugging the body when the vehicle begins to go where it is supposed to.


Quote
How is the 8 kPa dynamic pressure arrived at? I'd like to include the equations in my spreadsheet if possible.

The 8 kPa dynamic pressure would decelerate the vehicle, correct? I am thinking the .36 km/s I have at the top is optimistic.
R7 might be referring to the atmospheric pressure of 8kPa at 18km altitude.

Not referring to the ambient pressure, just a coincidence that its almost the same.

http://en.wikipedia.org/wiki/Dynamic_pressure

q = 0.5 * rho * v2

Air density (rho) at 18km is 0.12kg/m3, speed 360m/s, when those are plugged into above equation it gives ~7.8kPa of dynamic pressure.

And yes that pressure drags the vehicle down. To calculate how much exactly you need the actual drag equation.

http://en.wikipedia.org/wiki/Drag_equation



Note how that begins with dynamic pressure.

Also worthy of note how the dynamic pressure is denoted by "q", that's what the q in "Max Q" means, maximum dynamic pressure.
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Offline pagheca

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #63 on: 12/31/2014 09:26 AM »
I do not think those equations can be applied to trans-, super- and hypersonic regimes. The result can be an order of magnitude or more larger.

Offline R7

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #64 on: 12/31/2014 09:35 AM »
Yes they can and are but the CD varies with speed so it's profile must be known for accurate modeling.



It also varies with angle of attack. Here example curves for V-2 missile;



(someone else scanned that from Rocket Propulsion Elements so don't blame me...)
« Last Edit: 12/31/2014 09:45 AM by R7 »
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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #65 on: 12/31/2014 10:08 AM »
Too bad we can't build an angled launch platform, effectively zero out the mass of a launch payload and launcher, let Earth's centripedial force fling the pacage upwards and gradually bring the effective mass back to normal to achievel orbit either around Earth or towards another planet.  Maybe the Alcubierre drive could achieve this from ground level?  Be kind of interesting to see what happens if it were activated in a gravity well anyway...

Even if you could dial the mass of an object up and down, it wouldn't do what you suggest.  Centrifugal force is proportional to the mass just like the force of gravity is.  The ratio is always the same at a given position on the Earth's surface or above it, and it doesn't depend on mass.

And the Alcubierre Drive is an idea for a configuration of space-time that would move faster than the speed of light.  It has nothing to do with changing the mass of an object.  The Alcubierre Drive is also known to be impossible with known physics -- as is changing the mass of an object without moving the mass somewhere else or converting it to an equivalent amount of energy.

Offline john smith 19

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #66 on: 01/01/2015 09:12 PM »

At Sea Level you will have a vehicle separating from its carrier at > Mach 1. I can't recall how Mach varies with air pressure but you'd be pretty close to the M1 drag "hump" but probably not far enough above it for the drag to have subsided before you'll need to start the engines.

If you're going with a sort of tipped over VTOL SSTO  you'll have quite seriously asymmetric forces on the vehicle and still need an engine system with thrust close to mass. If you go with winged configuration you'd be smart to put the engines near the Cg as you're probably wanting it back.

The full Mach range of a launch vehicle, relative to all other flying machines is huge. The massive fuel burn gives a huge Cg shift while the Mach range gives a huge Cp shift.

Before anyone points out "Maybe, but Shuttle handled it" I'll say Shuttle "handled it" by a)Throwing away the propellant tanks b)Having a must-never-fail package of APU/GPC/flight actuators  which had to be continuously running during landing and c) A landing speed and weight that meant the tires were good for 1 use.

All to cope with the fact that sticking the engines at the back makes you very tail heavy and a tail heavy glider is not a good idea to start with.  :(
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Offline Hop_David

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #67 on: 01/02/2015 06:50 PM »
AoA?

Angle of attack. If the vehicle has traditional rocket shape, pointy end forward, slim body and engines in the aft it must point the nose up and initially fly "sideways" to counter gravity and rise. That's tough on the structure.

Okay, I think I got you. An conventional rocket would still need to be vertically aligned if it's going to continue a vertical ascent. Here's a pic:



Quote
How is the 8 kPa dynamic pressure arrived at? I'd like to include the equations in my spreadsheet if possible.

The 8 kPa dynamic pressure would decelerate the vehicle, correct? I am thinking the .36 km/s I have at the top is optimistic.
http://en.wikipedia.org/wiki/Dynamic_pressure

q = 0.5 * rho * v2

Air density (rho) at 18km is 0.12kg/m3, speed 360m/s, when those are plugged into above equation it gives ~7.8kPa of dynamic pressure.

And yes that pressure drags the vehicle down. To calculate how much exactly you need the actual drag equation.

http://en.wikipedia.org/wiki/Drag_equation



Note how that begins with dynamic pressure.

Also worthy of note how the dynamic pressure is denoted by "q", that's what the q in "Max Q" means, maximum dynamic pressure.

Good stuff, thanks!

Wikipedia tells me earth's scale height is 8.5 km and that rho at sea level is 1.225 kg/m^3.

So using exp(-altitude/scale height) * 1.225 kg/m^3 I get a density a little higher but I'm hoping my procedure is generally correct. I'm attaching an attempted spreadsheet for drag force and dynamic pressure at different altitudes and speeds.

For the 18 km altitude at .36 km/s scenario I picked a drag coefficient of 1 since it's flying sideways through the atmosphere.
« Last Edit: 01/02/2015 06:53 PM by Hop_David »

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #68 on: 01/03/2015 02:32 PM »

At Sea Level you will have a vehicle separating from its carrier at > Mach 1.

Not at sea level. My illustration shows separation at the top of Chimborazo which is about 6400 meters. At this altitude I get air density about half that of sea level.

For .5 km/s and half of sea level density I get a dynamic pressure of about 72 kilo pascals.

I will admit I didn't know what kilo pascal dynamic pressure meant. So I tried to calculate quantitites to compare.

For Class 5 hurricane I get 2.8 kilo pascals
Googling max Q of space shuttle I see 442 m/s at 1100 m altitude which seems to be about 33 kilo pascals.

So using those numbers as a yardstick, 72 kPa seems very challenging.

I think I set up my spreadsheet correctly but dynamic pressure is new to me so take those numbers with a grain of salt.

-----

.5 km/s is about mach 1.5. Using the chart r7 posted and assuming a bullet shape I am guessing a drag coefficient of .4.

Using a drag coefficient of .4 and a space ship of approximately Falcon 9 dimensions I get a drag force of about 300,000 newtons. Since Falcon 9 is about 500,000 kg, that comes to an deceleration of .6 meters/sec^2.

The deceleration isn't as large as I thought it would be.

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #69 on: 01/03/2015 04:35 PM »
.5 km/s is about mach 1.5. Using the chart r7 posted and assuming a bullet shape I am guessing a drag coefficient of .4.

Using a drag coefficient of .4 and a space ship of approximately Falcon 9 dimensions I get a drag force of about 300,000 newtons. Since Falcon 9 is about 500,000 kg, that comes to an deceleration of .6 meters/sec^2.

The deceleration isn't as large as I thought it would be.

The drag isn't huge because your vehicle is quite massive and enjoys the benefits from cube-square law. Falcon 9 experiences greater drag deceleration because when it is going 0.5km/s it is already a lot lighter than 500000kg.

The spreadsheet looks OK. The simple scale height gives slightly different values for density because it assumes constant temperature. I got the number from online international standard atmosphere calculator. But in this case the scale height is quite good, simple and "close enough".

I like your illustration of rocket getting bent while going sideways, more telling about the predicament than thousand words  :D
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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #70 on: 01/05/2015 06:36 PM »
I'd think it would "bend" the other way though... :)

IIRC the "best" AoA is around 70 degress to the horizon until you get above the effective atmosphere. So it would come out of the rail, er, "Maglev" (grin) nose first at 30 degrees with the engines balancing the drag forces to keep itself "alinged" and increase the AoA to around 70 degrees till it gets above 100km.

Part of the reason the TMP "Bifrost" launcher went up the center of Kilamanjaro was to allow a built in "AoA" of a bit less than 90 degrees (I seem to recall it was somewhere between 75 and 85 but not sure) so the vehicle would not come back down on the mountain but be able to fight its way over to a gliding landing if need be.

The main problem with the idea was (among others) that the given length of the launcher and the needed "muzzle velocity" required somewhat over 12Gs worth of accelleration to accomplish and STILL needed the laser array to achieve orbital velocity. "Longer" track required a curve to keep the depth managable and it was clear with some calculation (later) that you couldn't make the curve shallow enough to NOT turn the passengers into strawberry jam. Suggestions on putting it up the "side" quickly ran into the difficulties of getting from about 30 degrees AoA to the needed over 70 degrees as noted here.

Then of course DC-X was flying and everyone got onto the bandwagon "assuming" that SSTO was just around the corner and the whole idea fell by the wayside.

The main problem with the idea is that mountains that "fit" the bill are hard to access.

Randy
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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #71 on: 01/20/2015 04:22 PM »
A booster starting it's burn at 18 km altitude and a horizontal velocity of .83 km/s has  some advantage over a regular booster.

There's also disadvantage; it has to start with very large AoA while surviving ~8 kPa dynamic pressure or have wings.

AoA?

How is the 8 kPa dynamic pressure arrived at? I'd like to include the equations in my spreadsheet if possible.

The 8 kPa dynamic pressure would decelerate the vehicle, correct? I am thinking the .36 km/s I have at the top is optimistic.



does everyone agree some numbers would work for something along these lines?

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #72 on: 01/30/2015 07:13 PM »
The spreadsheet looks OK. The simple scale height gives slightly different values for density because it assumes constant temperature. I got the number from online international standard atmosphere calculator. But in this case the scale height is quite good, simple and "close enough".

I used the spreadsheet to look at another question I've wondered about for years:

Is a mag lev up Olympus Mons a possible way to achieve orbit?

This Mars fact sheet gives Mars surface density as .02 kg/m^3 and scale height as 11 km. Altitude of of Olympus Mons is about 22 km. Mars orbital velocity is about 3.5 km/s.

Plugging these numbers into my spreadsheet I got a dynamic pressure of 17 kilo pascals. That's about half of the shuttle's max Q.

So I am guessing Mars' atmosphere isn't a show stopper for an Olympus Mons rail gun.

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #73 on: 11/17/2017 09:34 AM »
Does electric haulage (i.e. TESLA Semi) make high altitude operations and infrastructure any more viable?


Perhaps, making an upper-stage landing pad easier to construct.
« Last Edit: 11/17/2017 09:37 AM by gin455res »

Offline stefan r

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #74 on: 11/22/2017 07:44 PM »

1/2 good idea....not a launch site.  A space elevator build site  :D

a whole different game.

Right.  That would cut the cable length from 35,786 km to 35,780 km.  The transit time on the cable could also go down by 1.7% of 1%. 

The longest part of a plane ride is when you are at the gate but cannot leave your seat because people are blocking the isle.  Imagine traveling all the way back from Mars and then descending the cable for a week.  The last 5000 meters will be grueling.  You could see clouds and a horizon but you are still stuck in that can with the same smelly co-pilot. 

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #75 on: 11/22/2017 08:24 PM »
Does electric haulage (i.e. TESLA Semi) make high altitude operations and infrastructure any more viable?


no

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #76 on: 12/03/2017 03:24 AM »

So I am guessing Mars' atmosphere isn't a show stopper for an Olympus Mons rail gun.

From Olympus Mons you would need a rocket to straighten out the 18 degree north. 

Pavonis Mons is at the equator.  It is 14km so would have a lot more air than Olympus Mons.  Arsia Mons has 20 km peak around 10 degrees south.  The northern part of the caldera is lower but gets closer to 8 degrees south. 

Pavonis Mons gets equatorial sunlight, it likely has glaciers, and there are some nifty lava tubes.  The rail gun only needs to reach the Phobos tether. 

Offline Norm38

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #77 on: 12/05/2017 12:10 AM »
If we consider reusable rockets, the F9 uses the thick atmosphere to slow down. What’s the fuel penalty for F9 to land at 19,000 feet?

And I always thought the point of Kilimanjaro was to rocket sled up the slope and launch already at some speed.

Offline bmcgaffey20

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #78 on: 12/06/2017 04:57 PM »
I didn't read the contents of this entire thread yet.... but I had a similar idea when I was a teenager. This idea wasn't for manned launches to space.

I was contemplating the possibility of constructing a large scale rail-gun style payload delivery system. I wanted to know if it was possible to launch a small payload via nuclear powered rail gun launched from the top of a very high mountain. Additionally, the payload should be constructed as a ram-jet assisted rocket. (Charge up the railgun, and fire it... assist with real second stage style rocket engines).

Offline Paul451

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #79 on: 12/11/2017 09:59 AM »
Not sure why this thread is zombified, but since it is:

Why bother with existing mountains? Build your own.

Open frame towers can be built taller than the tallest buildings for orders of magnitude lower costs. For a long time, antenna masts had to be excluded from "tallest building in the world" records, because of they always won. (We don't really need tall antennas any more, so buildings are back in front.)

For the price of Burj Khalifa, and with no exotic materials, you could go many, many times taller with a simple open frame tower. Above the bulk of the atmosphere, taller than any mountain. String many such towers in a row near the equator and hang a long platform from the top like a suspension bridge, but upwardly sloping towards the east. Run a rail up the length. Launch a rocket on a sled on the rail.

Perhaps the "first stage" would be permanently mounted to the sled, braking before the end, fully and immediately reusable. "Second" stage would ignite during the loft towards apogee after it leaves the end of the platform.

Sure it would cost billions. And billions. But how much has SLS cost so far?

Online hkultala

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #80 on: 12/11/2017 10:06 AM »
Not sure why this thread is zombified, but since it is:

Why bother with existing mountains? Build your own.

Open frame towers can be built taller than the tallest buildings for orders of magnitude lower costs. For a long time, antenna masts had to be excluded from "tallest building in the world" records, because of they always won. (We don't really need tall antennas any more, so buildings are back in front.)

For the price of Burj Khalifa, and with no exotic materials, you could go many, many times taller with a simple open frame tower. Above the bulk of the atmosphere, taller than any mountain. String many such towers in a row near the equator and hang a long platform from the top like a suspension bridge, but upwardly sloping towards the east. Run a rail up the length. Launch a rocket on a sled on the rail.

Perhaps the "first stage" would be permanently mounted to the sled, braking before the end, fully and immediately reusable. "Second" stage would ignite during the loft towards apogee after it leaves the end of the platform.

Sure it would cost billions. And billions. But how much has SLS cost so far?

An antenna mast has to hold an antenna and basestation that weight maybe some tens of kilograms.
And the weight of a 100kg maintainance person.

A heavy lift rocket weighs over million kilograms.

Bulding a super-high tower for launch use MUCH more expensive than you think.
« Last Edit: 12/12/2017 11:57 AM by hkultala »

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #81 on: 12/11/2017 10:46 AM »
For the price of Burj Khalifa, and with no exotic materials, you could go many, many times taller with a simple open frame tower.
For the price of Burj Khalifa you can launch 21 Falcon 9 disposable rockets.
What about maintenance and operational costs? Forget it, the improvement is marginal compared to the costs.

Sure it would cost billions. And billions. But how much has SLS cost so far?
Compare with commercial launch providers, not with SLS.

Offline gin455res

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #82 on: 12/11/2017 01:17 PM »
If we consider reusable rockets, the F9 uses the thick atmosphere to slow down. What’s the fuel penalty for F9 to land at 19,000 feet?

And I always thought the point of Kilimanjaro was to rocket sled up the slope and launch already at some speed.

I'm interested if an upper-stage with perhaps 3 or 5 engines would gain any useful ISP improvement (on the way up) with a higher expansion-ratio* central landing engine, and/or any engine mass reduction** that might end up in an improvement in mass fraction.

*enabled by a high altitude landing pad
**enabled by better T/W after staging. i.e. all engines thrusting for longer after staging, instead of just the vacuum engines. Might this allow the engine to be slightly downsized?
And what constrains landing engine expansion ratio, landing air pressure or 'effective air pressure' during supersonic retro-propulsion?

Offline RobLynn

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #83 on: 12/11/2017 10:04 PM »
19000 feet engine Isp would only be something like 5% higher than at sea level.  with air density about half of sea level terminal velocity will be approximately 40% higher, so would need something like 40% more landing fuel.
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Offline 2008rlctx

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #84 on: 06/08/2018 08:44 PM »
Reviving this old thread!

Does anyone know of any threads that consider the effect on this idea of tunneling (a la BoringCompany) straight down into the mountain as deep as you'd like to go with the intent to then evacuate said tunnel of air for a launch, thus eliminating air resistance for the first 18km of the 100km? The first 18km also having the highest density of air compared to the rest of the 82km distance to space. Per this link: https://upload.wikimedia.org/wikipedia/commons/9/9d/Comparison_US_standard_atmosphere_1962.svg , the density of air at 18km seems to be about 1/10 of that at sea level. So this concept would get you past 90% of the air?!

One step further, the "first stage" could be integrated into the tunnel via a vertical electric sled that accelerated the LV as much as possible and stayed in the tunnel.

Some type of system would need to be employed to keep the air out during the LV's trip through the tunnel, as well as release the LV out the end, but doesn't seem like an insurmountable obstacle.

Offline Phil Stooke

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #85 on: 06/08/2018 08:56 PM »
Wouldn't you need a mountain 18 km tall to make that work? 

Offline 2008rlctx

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #86 on: 06/08/2018 08:58 PM »
Ooops...it appears as though I misread the picture posted in the thread. The Mountain is much shorter. Back to reality.

Offline Paul451

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #87 on: 06/09/2018 10:12 AM »
In addition to the height thing...

the density of air at 18km seems to be about 1/10 of that at sea level. So this concept would get you past 90% of the air?!

The air inside the tunnel will have the same height-variance as the air outside. So if you evacuate it to 10% pressure at the bottom of the tube, it will be much less than outside air pressure at 18km. Hence you'll still have the problem of hitting a wall of pressure as you exit.

Offline deruch

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #88 on: 06/13/2018 11:35 AM »
Back to reality.

Oh, there goes gravity.
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline tl6973

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #89 on: 06/13/2018 01:08 PM »
Reviving this old thread!

Does anyone know of any threads that consider the effect on this idea of tunneling (a la BoringCompany) straight down into the mountain as deep as you'd like to go with the intent to then evacuate said tunnel of air for a launch, thus eliminating air resistance for the first 18km of the 100km? The first 18km also having the highest density of air compared to the rest of the 82km distance to space. Per this link: https://upload.wikimedia.org/wikipedia/commons/9/9d/Comparison_US_standard_atmosphere_1962.svg , the density of air at 18km seems to be about 1/10 of that at sea level. So this concept would get you past 90% of the air?!

One step further, the "first stage" could be integrated into the tunnel via a vertical electric sled that accelerated the LV as much as possible and stayed in the tunnel.

Some type of system would need to be employed to keep the air out during the LV's trip through the tunnel, as well as release the LV out the end, but doesn't seem like an insurmountable obstacle.

You need to read Terminal World by Alastair Reynolds :-)

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #90 on: 06/13/2018 09:18 PM »
Reviving this old thread!

Does anyone know of any threads that consider the effect on this idea of tunneling (a la BoringCompany) straight down into the mountain as deep as you'd like to go with the intent to then evacuate said tunnel of air for a launch, thus eliminating air resistance for the first 18km of the 100km?


You cannot easily both keep the air out and also let the rocket out

You would need some kind of huge air-tight doors, but the millisecond you start opening the doors, the tunnel starts to pressurize at huge speed, and the rocket hits a huge wave of air dropping very fast from the opening.

Some kind of huge airlock might help and decrease the mass of the air in the wave, but flying through an airlock at very high speed does not sound very safe..

Offline Asteroza

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #91 on: 06/14/2018 12:00 AM »
Don't most designs have a mixed exit technology setup, with a primary physical airlock door, and a plasma window that the projectile/spacecraft passes through?

Offline Paul451

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #92 on: 06/14/2018 03:01 AM »
Don't most designs have a mixed exit technology setup, with a primary physical airlock door, and a plasma window that the projectile/spacecraft passes through?

Out of curiosity, what's the largest plasma window anyone has produced?

[edit: My reason for asking is that looking around the googles, the diameter numbers are typically given in single-digit millimetres, not multiple metres.]
« Last Edit: 06/14/2018 04:32 PM by Paul451 »

Offline RobLynn

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #93 on: 06/14/2018 08:41 AM »
You cannot easily both keep the air out and also let the rocket out

You would need some kind of huge air-tight doors, but the millisecond you start opening the doors, the tunnel starts to pressurize at huge speed, and the rocket hits a huge wave of air dropping very fast from the opening.

Some kind of huge airlock might help and decrease the mass of the air in the wave, but flying through an airlock at very high speed does not sound very safe..

Even at 10m diameter it would be quite feasible to fully open a door in less than 0.1s - About 50g opening acceleration on two half doors would suffice.  Magnetically restrained pneumatic rams, pyrotechnic ram actuators etc.

The air running down the end of the opening tube is (from bernoullis equation) at just the same total pressure (dynamic+static) as the outside air.  A ring of high powered steam nozzles at 45° to nozzle end might also provide some reduction in inflow.

Capital costs, siting issues and inflexible trajectories of catapults make them unlikely choice for foreseeable future.  air-augmented boosters of some type (like tip-rocket driven transonic fans similar to Roton concept) might eventually have a chance if flight rates are high enough to cover their higher development cost.
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Offline IRobot

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #94 on: 06/14/2018 10:43 AM »
Reviving this old thread!
Please, please, please, let bad ideas die!

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #95 on: 06/14/2018 10:52 AM »
Reviving this old thread!
Please, please, please, let bad ideas die!
Or find a billion dollars, and build a launch pad on top of Kilimanjaro. That'd be cool too.

Offline sghill

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #96 on: 06/14/2018 12:58 PM »
Reviving this old thread!

Does anyone know of any threads that consider the effect on this idea of tunneling (a la BoringCompany) straight down into the mountain as deep as you'd like to go with the intent to then evacuate said tunnel of air for a launch, thus eliminating air resistance for the first 18km of the 100km?


You cannot easily both keep the air out and also let the rocket out

You would need some kind of huge air-tight doors, but the millisecond you start opening the doors, the tunnel starts to pressurize at huge speed, and the rocket hits a huge wave of air dropping very fast from the opening.

Some kind of huge airlock might help and decrease the mass of the air in the wave, but flying through an airlock at very high speed does not sound very safe..

Let it burst through several bladders of reinforced cellophane or something similar. It's not in a complete vacuum in the tunnel, just a partial one. Each bladder only needs one or two PSI difference between the next one. Then it becomes a balancing act between the burst strength of the bladder and the impact force the projectile experiences as it bursts through each new bladder.  The lower the burst strength, the less impact the projectile feels, but the more bladders are needed. It is easy to replace each bladder between flights. Just slide in a new "wafer" and pull out the old ones.

BTW, Kilimanjaro is a world heritage site. It won't be the launch site mountain. Something in the Andes would fit the bill nicely though. :)
Bring the thunder!

Offline Paul451

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #97 on: 06/14/2018 04:59 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.

BTW, Kilimanjaro is a world heritage site. It won't be the launch site mountain. Something in the Andes would fit the bill nicely though.

Well, if we're dreaming up magic launch systems, why not just build a stay-supported tower at the required height, hang the launch tube from that. With modern materials and engineering, you should be able to go higher than a mountain. And probably cheaper than drilling a vertical shaft through a mountain. Or if money is no object, then using the most advanced composites, you might be able to get a line of towers up around 30-50km in height, running a few hundred km or so across a suitably friendly continent. Then your launch rail can be open-air and mostly horizontal (30°?). Add more sections as technology improves, going higher and longer, until you've got a 1000km line going up to 100km release point; 4g on the rail and no need for a second stage to LEO, just a circularisation burn.

Offline Kaputnik

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #98 on: 06/14/2018 06:52 PM »
Reviving this old thread!

Does anyone know of any threads that consider the effect on this idea of tunneling (a la BoringCompany) straight down into the mountain as deep as you'd like to go with the intent to then evacuate said tunnel of air for a launch, thus eliminating air resistance for the first 18km of the 100km?


You cannot easily both keep the air out and also let the rocket out

You would need some kind of huge air-tight doors, but the millisecond you start opening the doors, the tunnel starts to pressurize at huge speed, and the rocket hits a huge wave of air dropping very fast from the opening.

Some kind of huge airlock might help and decrease the mass of the air in the wave, but flying through an airlock at very high speed does not sound very safe..


Would it not make more sense to open a door at the bottom of the shaft, allowing air pressure to surge up the shaft from behind the vehicle, thus giving it a boost? You would want to time this so that by the time the vehicle reaches the exit, there is little pressure differential between the air around it in the tube, and the air at the exit.
Waiting for joy and raptor

Offline Asteroza

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Re: Totally crazy idea: Space launch site on Mt Kilimanjaro?
« Reply #99 on: 06/15/2018 12:19 AM »
Don't most designs have a mixed exit technology setup, with a primary physical airlock door, and a plasma window that the projectile/spacecraft passes through?

Out of curiosity, what's the largest plasma window anyone has produced?

[edit: My reason for asking is that looking around the googles, the diameter numbers are typically given in single-digit millimetres, not multiple metres.]

I was under the impression that plasma windows proposed to cover the neutron spallation target of an accelerator driven subcritical nuclear reactor to separate the spallation target boiloff vapor from the particle accelerator beamline vacuum were somewhat large, but now that I think about it, the pressure difference would be a lot less than between atmosphere at the top of a mountain based vacuum tube and a vacuum accelerator tube.

That said, in literature a plasma window is usually mentioned as part of the muzzle exit architecture. Somebody clearly thought large diameter plasma windows are a thing (perhaps at increased energy cost)?

That sudden slamming by the spacecraft/projectile into the pressure differential is still pretty brutal however.

I wonder if you could cheat a little, by using inflatable rings strung together to form a long hollow floating tube anchored to the muzzle and appropriately tethered to match the trajectory, and shift the airlock/plasma window to the top of of the floating tube, where the pressure inside the inflatable tube hollow zone more closely matches the atmosphere at the top of the tube. You get no acceleration in the floating tube, but you do get an evacuated pathway to a lower pressure region.

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 »
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