For Questions That Don't Merit Their Own Thread

[RainDreamer]

Assuming humanity some how magically unite and ignore pesky things like borders, where are some of the best place on Earth for building launch pads and develop space programs?

[fredinno]

9 hours ago, nohelmet said:

Assuming that is true, it would mean we need the ring's center of mass nearer the planet than the ring. Since the ring spins around its CoM, then they won't collide.

More precisely, we need the distance from CoM to planet + planet radius to be smaller than the distance from CoM to nearest ring point.

Ringworlds are by definition unstable, regardless. One small push can cause the ring to eventually colllide.

[andrewas]

13 hours ago, nohelmet said:

Assuming that is true, it would mean we need the ring's center of mass nearer the planet than the ring. Since the ring spins around its CoM, then they won't collide.

More precisely, we need the distance from CoM to planet + planet radius to be smaller than the distance from CoM to nearest ring point.

The closer to the planet the CoM is, the closer the mass distribution is to a simple ring - and we know those are unstable. I don't know if theres a sweet spot, where the CoM is far enough away from the planet to orbit more or less normally, but close enough to the planet that the ring can't collide. I would guess not, but I can't prove it.

[Budgie]

On March 11, 2016 at 5:56 AM, RainDreamer said:

Assuming humanity some how magically unite and ignore pesky things like borders, where are some of the best place on Earth for building launch pads and develop space programs?

Hmmm. Looking at a map, I'd say any east coast site on or near the equator. ESA's Korou spaceport is in a pretty good location, honestly. 

[fredinno]

On 3/11/2016 at 1:54 PM, andrewas said:

The closer to the planet the CoM is, the closer the mass distribution is to a simple ring - and we know those are unstable. I don't know if theres a sweet spot, where the CoM is far enough away from the planet to orbit more or less normally, but close enough to the planet that the ring can't collide. I would guess not, but I can't prove it.

http://physics.stackexchange.com/questions/41254/why-is-larry-nivens-ringworld-unstable

Nope, unstable regardless.

[nohelmet]

On 3/11/2016 at 9:02 AM, fredinno said:

Ringworlds are by definition unstable, regardless. One small push can cause the ring to eventually colllide.

That is known for stationary rings, but I don't know about spinning ones. Do you have something more in-depth you could link to? The stackexchange link below only talks about stationary rings. 

[fredinno]

5 hours ago, nohelmet said:

That is known for stationary rings, but I don't know about spinning ones. Do you have something more in-depth you could link to? The stackexchange link below only talks about stationary rings. 

https://en.wikipedia.org/wiki/Ringworld

Nope, still unstable.

[nohelmet]

On 3/16/2016 at 7:38 PM, fredinno said:

https://en.wikipedia.org/wiki/Ringworld

Nope, still unstable.

I believe you, yet I still don't understand. They say "Ringworld, being a rigid structure, does not orbit." I don't quite see how being rigid would be an obstacle to stability. I can imagine a structure that is rapidly spinning around its CoM, said CoM turning around a planet. I don't know how to convince myself either that this can work, or that it can't. 

In the earlier posts we eliminated the options of "the moon with a hoop" (the moon is spinning so the hoop would collide with earth) and "a ring that is not spinning." That doesn't eliminate all the options though.

[fredinno]

4 hours ago, nohelmet said:

I believe you, yet I still don't understand. They say "Ringworld, being a rigid structure, does not orbit." I don't quite see how being rigid would be an obstacle to stability. I can imagine a structure that is rapidly spinning around its CoM, said CoM turning around a planet. I don't know how to convince myself either that this can work, or that it can't. 

In the earlier posts we eliminated the options of "the moon with a hoop" (the moon is spinning so the hoop would collide with earth) and "a ring that is not spinning." That doesn't eliminate all the options though.

In the novel, the Ringworld is spinning, and it was still touted as unstable- any force on the ring will cause ever increasing changes in the position of thering, causing it to collde into the host object.

[andrewas]

9 hours ago, nohelmet said:

I believe you, yet I still don't understand. They say "Ringworld, being a rigid structure, does not orbit." I don't quite see how being rigid would be an obstacle to stability. I can imagine a structure that is rapidly spinning around its CoM, said CoM turning around a planet. I don't know how to convince myself either that this can work, or that it can't. 

You can't treat a ringworld as a point mass at the CoM, because the primary is inside the ring and much of the ring's gravity is cancelled out by the other side of the ring. WIth a simple ring perfectly centered, everything cancels. Perturb the ring slightly and the gravity from the low side overpowers the gravity from the high side, and the ring is pulled further out of position until it impacts the primary.

9 hours ago, nohelmet said:

In the earlier posts we eliminated the options of "the moon with a hoop" (the moon is spinning so the hoop would collide with earth) and "a ring that is not spinning." That doesn't eliminate all the options though.

No, but as far as I can see you can't do more than stabilize the ring in one horizontal axis. Complete stability appears to be impossible.

 

[PB666]

On 3/11/2016 at 3:54 PM, andrewas said:

The closer to the planet the CoM is, the closer the mass distribution is to a simple ring - and we know those are unstable. I don't know if theres a sweet spot, where the CoM is far enough away from the planet to orbit more or less normally, but close enough to the planet that the ring can't collide. I would guess not, but I can't prove it.

https://en.wikipedia.org/wiki/Chimborazo

Would be excellent for small efficient rockets with reccurent payloads, like those going to resupply the space station, but especially missions to GSO.

This is the furthest point on the earth from the center of the earth, its flat on top. One of the problems with launching small rockets is known as side drag, often not considered but has a disproportion affect the smaller the crosssectional area per any give height rockets as we know based on recent studies solar electric rockets are far better in small builds, equipped with ion drives these small vehicles will someday become the means of truck supplies all around the solar system, the problem is getting the small things into space. One strategy (cubesat) is to release a bunch of them from a single rocket. A second strategy is find someplace to launch were drag is less of a concern. So now lets consider a launch were a spacecraft reaches mach 1. I solved this problem in KSP by placing my launchpads on minmus and gilly, the next one will be moho. I also have one on the tallest mountain on Eve at around 7500 elev.

At MSL the space craft climbs as the speed of sound falls with temperature, around 330m/s if thrust to mass ratio is 2(g) then that is 19.6 m/s at this acceleration Mach is reached in 33 =  (330 / (19.6-9.8)) seconds. This is a distance of 5336 (0.5 * 9.8 * 33^2) meters or about 18,000 feet. The really critical speed for a rocket depends on design, but a reasonable aerodynamic rocket starts feeling Mach effects at about 0.95 Mach. At 5300 meter at the equator the speed of sound will be 330 meters per second were the atmospheric pressure is 0.6.

So lets us now start our ascent from chimbosama, This time we reach speed of sound sooner 4490 meters (300 m/s but at a much lower pressure) Elev = 4490 + 6000 = 10490 meters and pressure is 23.3/57ths that of an MSL start.

This has two consequences,

Motor down for maximum dynamic pressure means that the craft does not need as much fairing mass to protect the payload, which means it can carry more payload, it can repower to full throttle. 
The gravity at the top of the mountain is slightly lower and falls off more quickly.
The surface velocity is higher
The rate of acceleration past Maximum dynamic pressure can be faster because the atmosphere is thinning more quickly. The amount of acceleration for any given thrust will be slightly higher because the rocket is further from the averalge elevation of the year.

If say 0.5 meters is the maximum diameter rocket you can launch at Sea level, from the top of Chimbosama you can launch rockets of 0.30 meters.

Having said this the mountain has religious meaning to the local indigenous population.
 

[fredinno]

4 hours ago, PB666 said:

https://en.wikipedia.org/wiki/Chimborazo

Would be excellent for small efficient rockets with reccurent payloads, like those going to resupply the space station, but especially missions to GSO.

This is the furthest point on the earth from the center of the earth, its flat on top. One of the problems with launching small rockets is known as side drag, often not considered but has a disproportion affect the smaller the crosssectional area per any give height rockets as we know based on recent studies solar electric rockets are far better in small builds, equipped with ion drives these small vehicles will someday become the means of truck supplies all around the solar system, the problem is getting the small things into space. One strategy (cubesat) is to release a bunch of them from a single rocket. A second strategy is find someplace to launch were drag is less of a concern. So now lets consider a launch were a spacecraft reaches mach 1. I solved this problem in KSP by placing my launchpads on minmus and gilly, the next one will be moho. I also have one on the tallest mountain on Eve at around 7500 elev.

At MSL the space craft climbs as the speed of sound falls with temperature, around 330m/s if thrust to mass ratio is 2(g) then that is 19.6 m/s at this acceleration Mach is reached in 33 =  (330 / (19.6-9.8)) seconds. This is a distance of 5336 (0.5 * 9.8 * 33^2) meters or about 18,000 feet. The really critical speed for a rocket depends on design, but a reasonable aerodynamic rocket starts feeling Mach effects at about 0.95 Mach. At 5300 meter at the equator the speed of sound will be 330 meters per second were the atmospheric pressure is 0.6.

So lets us now start our ascent from chimbosama, This time we reach speed of sound sooner 4490 meters (300 m/s but at a much lower pressure) Elev = 4490 + 6000 = 10490 meters and pressure is 23.3/57ths that of an MSL start.

This has two consequences,

Motor down for maximum dynamic pressure means that the craft does not need as much fairing mass to protect the payload, which means it can carry more payload, it can repower to full throttle. 
The gravity at the top of the mountain is slightly lower and falls off more quickly.
The surface velocity is higher
The rate of acceleration past Maximum dynamic pressure can be faster because the atmosphere is thinning more quickly. The amount of acceleration for any given thrust will be slightly higher because the rocket is further from the averalge elevation of the year.

If say 0.5 meters is the maximum diameter rocket you can launch at Sea level, from the top of Chimbosama you can launch rockets of 0.30 meters.

Having said this the mountain has religious meaning to the local indigenous population.
 

And what is the cost for building a new Launch complex in the middle of nowhere, and building the infrastructure to support it?

[PB666]

1 hour ago, fredinno said:

And what is the cost for building a new Launch complex in the middle of nowhere, and building the infrastructure to support it?

Well they are going to build a space port in Boca Chica, not many people have been to boca chica, but I have, its not exactly the middle of somewhere.

 

[DerekL1963]

3 hours ago, PB666 said:

4 hours ago, fredinno said:

And what is the cost for building a new Launch complex in the middle of nowhere, and building the infrastructure to support it?

Well they are going to build a space port in Boca Chica, not many people have been to boca chica, but I have, its not exactly the middle of somewhere.

 

Doesn't have to be in the middle of somewhere - it has rail access, highway access, water access, and air access.   Chimborazo not so much.

[shynung]

I must mention that rail vehicles have limits to the physical size of the things they can transport. Most Russian rockets, including Proton and Soyuz, are generally designed around the biggest propellant tanks that the trains transporting them can carry, among other things, because their launch pad was in the middle of a continent. US and ESA rockets don't have that requirement because their launch pads are close to large bodies of water, so they can transport rocket parts by barge or ship.

Also, trains are very bad at climbing hills. Building a launch pad at the top of a mountain would necessitate the construction of a very powerful transport system in an entirely new class of its own.

[PB666]

6 hours ago, DerekL1963 said:

Doesn't have to be in the middle of somewhere - it has rail access, highway access, water access, and air access.   Chimborazo not so much.

Rail, boca, no, boca has sand, lots of it, it has lots of spanish dagger, rattlesnakes, aliens, border patrol agents, a plaque signifying the last battle of the civil war.

 

6 hours ago, shynung said:

I must mention that rail vehicles have limits to the physical size of the things they can transport. Most Russian rockets, including Proton and Soyuz, are generally designed around the biggest propellant tanks that the trains transporting them can carry, among other things, because their launch pad was in the middle of a continent. US and ESA rockets don't have that requirement because their launch pads are close to large bodies of water, so they can transport rocket parts by barge or ship.

Also, trains are very bad at climbing hills. Building a launch pad at the top of a mountain would necessitate the construction of a very powerful transport system in an entirely new class of its own.

Im surprise that no one has mentioned that this is a volcano, I would be more concerned about shifting surfaces and a train.

[shynung]

1 hour ago, PB666 said:

Im surprise that no one has mentioned that this is a volcano, I would be more concerned about shifting surfaces and a train.

An inactive volcano at that.

[p1t1o]

Is anyone imagining stoopidly impractical ways to use a volcano to launch things into space now?

[DerekL1963]

3 hours ago, PB666 said:

10 hours ago, DerekL1963 said:

Doesn't have to be in the middle of somewhere - it has rail access, highway access, water access, and air access.   Chimborazo not so much.

Rail, boca, no, boca has sand, lots of it, it has lots of spanish dagger, rattlesnakes, aliens, border patrol agents, a plaque signifying the last battle of the civil war.

Funny.  I guess the rail lines marked on the map and visible in the imagery are figments of Google's imagination then.  (Or not.)   Rail doesn't have to go all the way to the site to be very useful.

[PB666]

59 minutes ago, DerekL1963 said:

Funny.  I guess the rail lines marked on the map and visible in the imagery are figments of Google's imagination then.  (Or not.)   Rail doesn't have to go all the way to the site to be very useful.

Let me put it this way, the last time I went there there was no rail to speak of, rail may have been added. There are rail lines close to brownsville, and there is a road call bocachica hiway, but its 20 miles down were the south bay of the laguna madre  is a pinch between the lower rio grande and bay is what I call boca-chica, and there ain't no rail. It turns out I walked 16 miles from the south jetty of the brownsville ship channel down the beach and up bocachica hiway, I did get a pretty good view of the lay of the land.

[fredinno]

3 hours ago, p1t1o said:

Is anyone imagining stoopidly impractical ways to use a volcano to launch things into space now?

Are you Jebadiah Kerman?

1 hour ago, PB666 said:

Let me put it this way, the last time I went there there was no rail to speak of, rail may have been added. There are rail lines close to brownsville, and there is a road call bocachica hiway, but its 20 miles down were the south bay of the laguna madre  is a pinch between the lower rio grande and bay is what I call boca-chica, and there ain't no rail. It turns out I walked 16 miles from the south jetty of the brownsville ship channel down the beach and up bocachica hiway, I did get a pretty good view of the lay of the land.

Those rail lines could have just been added in support of the nearby inhabitants, and not exclusively for a rocket launch site. The volcano being proposed is very rural.

[PB666]

On 3/21/2016 at 4:10 PM, fredinno said:

Are you Jebadiah Kerman?

Those rail lines could have just been added in support of the nearby inhabitants, and not exclusively for a rocket launch site. The volcano being proposed is very rural.

This is texas, only city folk do that.

Here is the map https://www.google.com/maps/place//@25.9504708,-97.3358189,3789m/data=!3m1!1e3!4m2!3m1!1s0x0:0x0!5m1!1e4?hl=en

I've walked from here. https://www.google.com/maps/place//@26.0506646,-97.1686094,946m/data=!3m1!1e3!4m2!3m1!1s0x0:0x0!5m1!1e4?hl=en

to here: https://www.google.com/maps/place//@26.063998,-97.1473019,237m/data=!3m1!1e3!4m2!3m1!1s0x0:0x0!5m1!1e4?hl=en

spending the night walked then to here: https://www.google.com/maps/place//@25.9974979,-97.1508183,473m/data=!3m1!1e3!4m2!3m1!1s0x0:0x0!5m1!1e4?hl=en

barefoot and then on to here: https://www.google.com/maps/place//@25.9636581,-97.2261384,947m/data=!3m1!1e3!4m2!3m1!1s0x0:0x0!5m1!1e4?hl=en

and back to here: https://www.google.com/maps/place//@25.9920605,-97.182792,237m/data=!3m1!1e3!4m2!3m1!1s0x0:0x0!5m1!1e4?hl=en

It not only hasn't changed, some of the houses that were along the route are gone, and some of it has been designated a park. There was no water (wells are all salted over, people got water off their roofs) and some people were using wind turbines for electricity. It is at i appears from the air, lots of brown sand (having walked 6 miles through it I know what it feels like).

you follow the map back to brownsville and tell me where there is sand. That gravel on oil based road is on aggragate will definitely not hold anything a train would hold, and there are no tracks. Just remember you cross south of the river and you are in mexico.

There is Space X control center. https://www.google.com/maps/place//@25.9873837,-97.1867307,237m/data=!3m1!1e3!4m2!3m1!1s0x0:0x0!5m1!1e4?hl=en

So nobody give me no stuff about boca chica being the queens conch, Its on a dirt road off another dirt road off a gravel aggregate road that is two lanes wide and no friggen rail for at least 10 miles on a sandy back beach with no water and pitiful electrical.

 

[SuperFastJellyfish]

Obviously, you weren't there for spring break like I was 15 years ago because you never would have left South Padre Island.  The chicks, man...the chicks... 

 

 

Edited March 21, 2016 by SuperFastJellyfish
Just easin' the tension

[PB666]

46 minutes ago, SuperFastJellyfish said:

Obviously, you weren't there for spring break like I was 15 years ago because you never would have left South Padre Island.  The chicks, man...the chicks... 

 

 

The pretty ones are on the other side of the river.

https://images.duckduckgo.com/iu/?u=http%3A%2F%2Fartprintsof.com%2F1024%2Fart-print-digital-file-of-a-cartoon-fat-woman-reading-a-romance-novel-and-sun-bathing-in-a-beach-chair-by-ron-leishman-86.jpg&f=1

[DerekL1963]

23 hours ago, PB666 said:

I've walked from here. https://www.google.com/maps/place//@26.0506646,-97.1686094,946m/data=!3m1!1e3!4m2!3m1!1s0x0:0x0!5m1!1e4?hl=en

to here: https://www.google.com/maps/place//@26.063998,-97.1473019,237m/data=!3m1!1e3!4m2!3m1!1s0x0:0x0!5m1!1e4?hl=en

Which means you were miles and miles from the railhead at Brownsville.  So, where you walked or slept the night or whatever is essentially meaningless.
 

23 hours ago, PB666 said:

So nobody give me no stuff about boca chica being the queens conch, Its on a dirt road off another dirt road off a gravel aggregate road that is two lanes wide

Here in the 21st century, we have the ability to build roads.