What performance improvement would a Falcon 9, for example, have if launched from such a launch site, nearly 20'000 ft up?
Still think it is worth the performance gains?
Most of the fuel used to get to orbit isnt used to go UP but to increase the velocity in the orbital direction.
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.
We need Mike Heney to tell us about a better site in South America.
Must be the best place on earth for SSTO launch
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.
If we use a mountain anyway, why not build an electromagnetic mass driver into the slope? The volcano will provide geothermal power. :-)
Quote from: fast on 12/19/2014 05:07 pmMust 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.
Quote from: fast on 12/20/2014 03:11 pmSSTO 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.
Quote from: fast on 12/20/2014 03:11 pmSSTO 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.
Quote from: Eerie on 12/20/2014 09:47 amIf 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!
Quote from: R7 on 12/20/2014 02:38 pmQuote from: Eerie on 12/20/2014 09:47 amIf 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
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.
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?
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.
The local indigenous population probably would not allow something like that. They barely let the telescopes be built on their sacred mountains.
Why the limitation to 0.5 km/s?
Thanks for the cartoon, Tass. However, LACK and EXCESS of O2 have completely different effects... Xkcd quite wrong on this account :)
Quote from: Vultur on 12/29/2014 02:25 amWhy 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.
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.
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.
Quote from: Hop_David on 12/28/2014 11:54 pmA 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.
R7 might be referring to the atmospheric pressure of 8kPa at 18km altitude.
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...
Quote from: Hop_David on 12/30/2014 08:40 pmAoA?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.
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.Quote from: R7 on 12/31/2014 09:01 amhttp://en.wikipedia.org/wiki/Dynamic_pressureq = 0.5 * rho * v2Air 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_equationNote 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.
http://en.wikipedia.org/wiki/Dynamic_pressureq = 0.5 * rho * v2Air 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_equationNote 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.
Quote from: Hop_David on 12/30/2014 08:40 pmAt Sea Level you will have a vehicle separating from its carrier at > Mach 1.
.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.
Quote from: R7 on 12/30/2014 11:18 amQuote from: Hop_David on 12/28/2014 11:54 pmA 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.
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".
1/2 good idea....not a launch site. A space elevator build site a whole different game.
Does electric haulage (i.e. TESLA Semi) make high altitude operations and infrastructure any more viable?
So I am guessing Mars' atmosphere isn't a show stopper for an Olympus Mons rail gun.
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?
For the price of Burj Khalifa, and with no exotic materials, you could go many, many times taller with a simple open frame tower.
Sure it would cost billions. And billions. But how much has SLS cost so far?
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.
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?!
Back to reality.
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.
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?
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?
You cannot easily both keep the air out and also let the rocket outYou 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..
Reviving this old thread!
Quote from: 2008rlctx on 06/08/2018 08:44 pmReviving this old thread!Please, please, please, let bad ideas die!
Quote from: 2008rlctx on 06/08/2018 08:44 pmReviving 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 outYou 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.
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.
Quote from: Asteroza on 06/14/2018 12:00 amDon'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.]
Quote from: sghill on 06/14/2018 12:58 pmLet 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.
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.
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.