DeltaV savings from equatorial Mountain launch

[Bryce Ring]

I apologise for mentioning it in the SpaceX thread.

http://forum.kerbalspaceprogram.com/threads/98067-SpaceX-Attempts-Falcon-9-First-Stage-Landing-on-Autonomous-Spaceport-Drone-Ship?p=1674918&viewfull=1#post1674918

I am still curious though. I have been told it was debunked as a stupid Idea. I can understand the practical costs such as money setting up such a launch pad and VAB, Safety issues with stray rockets hitting populated areas, location difficulties height and country, foreign boarders etc.

But how much would be saved?.

I can not find it here on the threads. Probably because I am A/ thick. and B/ not knowing what terms to search for.

Bryce Ring.

Edited January 17, 2015 by Bryce Ring

[Ikaneko]

The closest mountain to the equator is in Colombia or some place. It's about 4000 metres tall, so the DV benefits are quite small. It would also take a helluva lot of money, not to mention trying to find out how to get your booster + delicate payload up a mountain.

Also Colombia wouldn't like it much. Or is it Ecuador?

TL;DR No.

[PakledHostage]

You might want to refer to some of the discussion in this thread: Pros/cons of launching at higher altitudes vs higher latitudes.

[maccollo]

Tried this with realism overhaul, using the SLS. I was able to save 140 m/s from launching from an altitude of 5 km. It appears to biggest contributing factor is the higher TWR and ISP at liftoff.

This resulted in me being able to throw 4 more tonnes to a 200x200 km orbit, or a payload increase of about 3%. It's not insignificant, but not that significant either given the effort it would require.

[Nibb31]

Of course, the effect is exagerated in KSP, so you can't really use it as an accurate simulation. In RL, the difference in atmospheric pressure is much less significant, and the altitude gains you nothing, because getting to orbit is not about altitude anyway, but about speed.

You'd be lucky to 200m/s in dV. You need 9500m/s to reach orbital speed, so the gain is less than 0.5%.

[AngelLestat]

I dint make any calculation, but I guess as macollo said, that is notice in the extra payload that you can launch.

Higher altitude + equator I assume a 4% to 7% extra payload mass.

But the problems to deal with third world countries (which may change agreements once over time) and all the transportation and location of the personal, not worth it, even if you have a full reusable rocket that go backs to your mountain.

Another place may be Mount Kenya in afrika, 5500 mts over the equator. But just as a mental exercise, the cons are huge.

But well, ESA seems that it will use a similar location for its capsule test.

Edited January 17, 2015 by AngelLestat

[Bryce Ring]

You might want to refer to some of the discussion in this thread: Pros/cons of launching at higher altitudes vs higher latitudes.

thanks for the link

And than you all for you replies. I was looking at the altitude as not a gain potential energy. but an ability to pitch/yaw over earlier in T+ sence. thus allowing horizontal speed to be achieved earlier and getting gravity losses down.

it seems mind boggeling that the SpaceX rocket took 60 seconds to get to 5km and was only down range .9km and was only going 300 odd m/s then after the next 60 second its 35km up going 1K/s and is down range 14.5km. huge difference from. some thing I don't understand is going on.

Off to that thread to see if I can settle my thoughts on this

Thanks Again

Bryce Ring.

[AngelLestat]

One thing that we all forget and is not mention in that link that hostage gave to you..

Is the final orbit inclination you want end.

The need for a "plane change" to the zero degree inclination of geostationary orbit is eliminated, providing a major extra launch "boost". This allows 17.5%-25% more mass to be launched to geostationary orbit than the same rocket launched from Cape Canaveral, which is at 28.5 degrees north latitude.

Any orbital inclination could be reached, thus (for example) combining in one launch site the attainable inclinations of both Cape Canaveral and Vandenberg.

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

In fact a total of 38 commercial sats were launched from a mobile maritime platform in the equator.

So yes.. you have some benefics.

[Nibb31]

But well, ESA seems that it will use a similar location for its capsule test.

ESA launches from Kourou, which is a French territory. No dealings with foreign countries, close to the equator, a location close to the sea so that rockets and payloads can be conveniently transported with cargo ships.

[Bryce Ring]

Tried this with realism overhaul, using the SLS. I was able to save 140 m/s from launching from an altitude of 5 km. It appears to biggest contributing factor is the higher TWR and ISP at liftoff.

This resulted in me being able to throw 4 more tonnes to a 200x200 km orbit, or a payload increase of about 3%. It's not insignificant, but not that significant either given the effort it would require.

Finally got RSS to work. RO crashed, with RSS I have set up MechJeb2, FAR, LazTech SpaceX LR craft files (HD's crashed my game), ISP Difficulty Scaler, and Kerbal Konstructs.

For the purpose of doing some self sub educational empirical testing, What other mods Should I consider?

Also. I wonder , Should I call MECO with SpaceX Dragon Explorer V2 the point where I reach Alt? And Velocity??

Any suggestions regarding MECO points and further Testing . (Yes I know its just KSP, but its all I got, can't do math lol)

Edited January 18, 2015 by Bryce Ring

[Bryce Ring]

Some preliminary testing.

Started from just over 100m ASL

Started from just under 4.7km

Initiated MECO at 2km/s surface speed.

More testing to be done.

Edited January 19, 2015 by Bryce Ring

[maccollo]

For the purpose of doing some self sub educational empirical testing, What other mods Should I consider?

Real, fuels as it makes thrust scale with ISP, and increased thrust to weight ratio is likely a major factor in the 100-200 m/s reduction.

[AngelLestat]

try as I said, put a payload in geo orbit, one time from Cape Canaveral, the second from the equator. If all works fine, you will notice an increase of 25% in the mass of the payload.

[Bryce Ring]

Real, fuels as it makes thrust scale with ISP, and increased thrust to weight ratio is likely a major factor in the 100-200 m/s reduction.

I worked myself into a head ache looking at Laz's SpaceX parts weights Thrusts ISPs etc and comparing to real world. It was also compounded by trying to work with KIDS mod and the ability to halt Fuel flow increase and change the thrust according to ISP changes, .....

Real Fuels you say eh lol, Not today , I need a beer.

Thanks for the info. I am going to looking at all the suggestions in the RO install (Those suggested when installing with CKAN)

Bryce.

- - - Updated - - -

try as I said, put a payload in geo orbit, one time from Cape Canaveral, the second from the equator. If all works fine, you will notice an increase of 25% in the mass of the payload.

I remember this when it was on a program here in asutralia called Beyond 2000 around 1995 I saw it.

http://www.amusingplanet.com/2013/03/sea-launch-launching-satellites-from.html

not sure if that is the one.

Bryce.

[Nibb31]

Use Orbiter if you want a realistic simulation. KSP is simply not up to the task, even with mods.

[AngelLestat]

I remember this when it was on a program here in asutralia called Beyond 2000 around 1995 I saw it.

http://www.amusingplanet.com/2013/03/sea-launch-launching-satellites-from.html

not sure if that is the one.

Bryce.

Yeah is that, I also remember that TV program.

This has economical sense if you know that you need to launch X amount of satellites of certain mass (very common in big communications proyects) and there is not other launcher that give you a good price with this amount of mass.

So if you already had a rocket design able to carry 10 tons, but you need 12. Then you build this barge and you launch from the equator.

Right now with the amount of different launchers, there is not much point to do these things.

[maccollo]

Use Orbiter if you want a realistic simulation. KSP is simply not up to the task, even with mods.

What differences are there that would have significant effects on the result in this case?

Edited January 20, 2015 by maccollo

[Bryce Ring]

What differences are there that would have a significant effects on the result in this case?

that is a good question. I am also interested in the answer and if there is actually a mod that can cure it.

I have been reading the Real fuel thread and NathanKell and ferram4 said that one mod tries to finagle its way through the ISP Fuel Flow Thrust ratios during transition between Atm densities/pressures and how they affect payload mass ratios. Click the link to view it, I don't fully or partial understand it yet, so I can not explain it

for now I am happy with the fix to fuel flow (IE Flow is constant), and how Thrust now varies with ISP and ISP varies with Atm.

Apart from that Finagle thing, I am interested in any other significant effects there would be to the results.

Back to you Nibb31

PS If anyone interested in playing with it.

Here are the RSS Launch site locations and Data (Be sure to have terrain detail high and to put it in Alphabetically into the list)

Site
    {
      name = eq_beachbum
      displayName = EQ - BeachBum
      PQSCity
      {
        KEYname = KSC
        latitude = 0.302780
        longitude = -79.898487
        repositionRadiusOffset = 62
        repositionToSphereSurface = false
        lodvisibleRangeMult = 6
      }
      PQSMod_MapDecalTangent
      {
        radius = 9500
        heightMapDeformity = 80
        absoluteOffset = 10
        absolute = true
        latitude = 0.302780
        longitude = -79.898487
      }
    }
Site
    {
      name = eq_Papallacta
      displayName = EQ - Papallacta
      PQSCity
      {
        KEYname = KSC
        latitude = 0.302780
        longitude = -78.198487
        repositionRadiusOffset = 4573
        repositionToSphereSurface = false
        lodvisibleRangeMult = 6
      }
      PQSMod_MapDecalTangent
      {
        radius = 4500
        heightMapDeformity = 80
        absoluteOffset = 4521
        absolute = true
        latitude = 0.302780
        longitude = -78.198487
      }
    }

[Tripod27]

Obviously you would get some deltaV savings from an equatorial mountain launch, since it increases both your rotational speed and decreases the height you have to travel, basically acting like a geostationary space elevator that you've only gone partway up

You can probably make an equation based off of geostationary being a deltaV zero point (good luck finding a mountain that tall) since at that point, you're in orbit just by being there, and then just calculate how much more deltaV it takes the lower down the "mountain"/space elevator you go until you get to sea level, making sure to add atmospheric effects once you go down to the part of the scale you're probably interested in

This would be based on your target orbit also being geostationary, but Its a start, and I failed physics class so give me a break =P

[Bryce Ring]

the savings are huge. I am still working on the setups and methods of comparison. but so far it looks considerable. if only it were a mountain with nothing but ocean immediately east of them and desolate islands scattered here and there to land on.

0.5% is awesome, F9 is over 500t and its payload (Not including dragon Capsule itself, Just the stuff that is delivered)is quoted to be 6t by SpaceX, Wiki puts it at 3.31t, that's so small compared to the launch pad weight, I cant even Math that one out =P , I think I have 50% chance of getting KSP to show it, or maybe I will just end up Crashing in Cuba some where, LOL bet they look up and say, That looks like a Giant Cigar, mouth drooling

[Nibb31]

There really is no point in doing trial and error test in a game with fantasy physics, when 5 minutes of Google-Fu answers your question:

http://www.wired.com/2011/07/space-shuttle-launch-equator-vs-mountains/

People have been doing the math for decades. The benefit of launching from the equator is real, but mainly for equatorial inclinations. It's one of the reasons why Ariane is such a good rocket for GTO launches. Launching from Kourou to an equatorial orbit provides an advantage of 200m/s compared to, for example, KSC. However, the biggest benefit is that it minimizes "dog-legging" when launching from a higher inclination. To launch from KSC to an equatorial orbit, you need to do a significant plane change of several hundred m/s of dV, which is not necessary when launching from the equator.

The reason why the US or Russia launch from higher inclinations is because at the time they built their launch sites, there wasn't really much point in launching to an equatorial orbit. Also, the logisitics and the strategic importance, meant that the site had to be part of the mainland, accessible with train lines or deep sea ports, with room for fuel production and storage facilities.

Launching from a mountain, on the other hand, is a silly idea. The benefit is insignificant and the logistics and political problems heavily outweigh the couple of m/s that you might gain.

Edited January 20, 2015 by Nibb31

[Bryce Ring]

There really is no point in doing trial and error test in a game with fantasy physics, when 5 minutes of Google-Fu answers your question:

http://www.wired.com/2011/07/space-shuttle-launch-equator-vs-mountains/

People have been doing the math for decades. The benefit of launching from the equator is real, but mainly for equatorial inclinations. It's one of the reasons why Ariane is such a good rocket for GTO launches. Launching from Kourou to an equatorial orbit provides an advantage of 200m/s compared to, for example, KSC. However, the biggest benefit is that it minimizes "dog-legging" when launching from a higher inclination. To launch from KSC to an equatorial orbit, you need to do a significant plane change of several hundred m/s of dV, which is not necessary when launching from the equator.

The reason why the US or Russia launch from higher inclinations is because at the time they built their launch sites, there wasn't really much point in launching to an equatorial orbit. Also, the logisitics and the strategic importance, meant that the site had to be part of the mainland, accessible with train lines or deep sea ports, with room for fuel production and storage facilities.

Launching from a mountain, on the other hand, is a silly idea. The benefit is insignificant and the logistics and political problems heavily outweigh the couple of m/s that you might gain.

Does The Equation assumes a launch ascent profile similar to that needed at sea level. with a mountain launch you can start your horizontal acceleration earlier and reduce Gravity loss.

Does The Equation assumes a ISP values will be the same throughout the launch as a sea level launch.

Are there any other Assumptions the Equation you linked to make.

if you can increase the load through the hatch to the ISS by 30% is that insignificant ?

PS what is wrong with KSP's physics with RSS, Real fuels, FAR, and the Basic RO installed (that would affect the results)?

Bryce Ring

- - - Updated - - -

Fantasy Physics Intermission

Just something to lighten the mood

[Nibb31]

Does The Equation assumes a launch ascent profile similar to that needed at sea level. with a mountain launch you can start your horizontal acceleration earlier and reduce Gravity loss.

In real-life, horizontal acceleration starts as soon as the rocket clears the tower. They don't "launch to 10000m and then start their gravity turn". It starts (gently) at 0m.

Unless your mountain launch site actually has the rocket sitting on a pad at an angle, your ascent profile will actually start at a higher altitude, ie: when a rocket launched from sea-level will be at 1 or 2 degrees at 5000m, your mountain-rocket will still be pointing straight up.

if you can increase the load through the hatch to the ISS by 30% is that insignificant ?

That claim doesn't match the math, which points to your simulation being wrong.

PS what is wrong with KSP's physics with RSS, Real fuels, FAR, and the Basic RO installed (that would affect the results)?

What makes you think that those plugins are realistic? They are more realistic than stock KSP, but they are still approximations. For one thing, launch profiles in RL take into account aerodynamic loads, which KSP doesn't. Point your supersonic rocket only a single degree off of its vector, and it will break up. This doesn't happen in KSP, where rockets can easily flip around and retro burn while flying at Mach 10. There is also the throttle and restart issue, which isn't simulated in KSP (real rocket engines don't throttle down, and when they do, it's never any lower that 70%). Also, the mass and tankage numbers for the hardware is very approximative, because many of those figures are not public. Sources such as Wikipedia or Astronautix are usually all over the place.

[Bryce Ring]

you have made a few Assumptions there.

Nibb31, I can tell you are not going to think about this, let alone help explain it. The link you provided was kinda useful, I thank you for that, but that link was inconclusive and did not connect the dots.

If you want me to explain the assumptions, I would be happy to do so, But I get the feeling you not really interested and have it stuck in you head its a stupid Idea just because some one else said so.

I will ask though, How much does 200m/s DeltaV weigh ?

Many questions I have asked but you have come back with silly assumptions rather than any solution or explanation why it may be wrong.

[Kryten]

I will ask though, How much does 200m/s DeltaV weigh ?

How long is a piece of string?