Rocket engines - from speculations to successful flights

[Loren Pechtel]

I think he's taking the usual far left big-tech-is-evil. Never mind that that's a prescription for the destruction of the human race.

You are very stupid if you think that.

Missile technology has endangered all of humanity.

We are much less safe because we have them.

Especially when morons elect people like Trump.

1) Most of the stuff listed isn't useful until you've reached orbit. Thus it's of absolutely zero value for ICBM use.

2) That's not a rebuttal to my point about the hazard of your small-scale approach. Obtaining resources generally requires big projects. Things like chip fabricators are big projects. Your society can't do big projects very well. Resource collapse, most everyone dies.

 

[untermensche]

I think he's taking the usual far left big-tech-is-evil. Never mind that that's a prescription for the destruction of the human race.

You are very stupid if you think that.

Missile technology has endangered all of humanity.

We are much less safe because we have them.

Especially when morons elect people like Trump.

1) Most of the stuff listed isn't useful until you've reached orbit. Thus it's of absolutely zero value for ICBM use.

2) That's not a rebuttal to my point about the hazard of your small-scale approach. Obtaining resources generally requires big projects. Things like chip fabricators are big projects. Your society can't do big projects very well. Resource collapse, most everyone dies.

What do you not understand about the fact that ICBMs make us less safe, not safer?

Sure they protect us from imaginary incredibly unlikely threats but they increase the threat from human stupidity and animal behavior.

 

[Loren Pechtel]

1) Most of the stuff listed isn't useful until you've reached orbit. Thus it's of absolutely zero value for ICBM use.

2) That's not a rebuttal to my point about the hazard of your small-scale approach. Obtaining resources generally requires big projects. Things like chip fabricators are big projects. Your society can't do big projects very well. Resource collapse, most everyone dies.

What do you not understand about the fact that ICBMs make us less safe, not safer?

Sure they protect us from imaginary incredibly unlikely threats but they increase the threat from human stupidity and animal behavior.

It's quite apparent that you did not understand what I was saying. The OP lists 9 drive systems. Less than half have any hope of lifting a rocket off the pad and one of those is extremely marginal. The two that are left are simply too big to propel an ICBM with.

Thus the only practical one for propelling ICBMs is the the one that's already used for the purpose.

You're just afraid of technology, there's no basis to fear these systems.

 

[untermensche]

1) Most of the stuff listed isn't useful until you've reached orbit. Thus it's of absolutely zero value for ICBM use.

2) That's not a rebuttal to my point about the hazard of your small-scale approach. Obtaining resources generally requires big projects. Things like chip fabricators are big projects. Your society can't do big projects very well. Resource collapse, most everyone dies.

What do you not understand about the fact that ICBMs make us less safe, not safer?

Sure they protect us from imaginary incredibly unlikely threats but they increase the threat from human stupidity and animal behavior.

It's quite apparent that you did not understand what I was saying. The OP lists 9 drive systems. Less than half have any hope of lifting a rocket off the pad and one of those is extremely marginal. The two that are left are simply too big to propel an ICBM with.

Thus the only practical one for propelling ICBMs is the the one that's already used for the purpose.

You're just afraid of technology, there's no basis to fear these systems.

You are allowed to have a childish fascination with missile technology.

But don't think these are great advancements and a great help.

They are probably going to kill all humans in some form.

 

[James Brown]

Well, this thread started off fun.

Perhaps the mods could step in here?

 

[untermensche]

No go on. Have your fun.

Dance your dances.

 

[fast]

Is there even a theoretical means of offsetting the forces felt by acceleration?

 

[bilby]

1) Most of the stuff listed isn't useful until you've reached orbit. Thus it's of absolutely zero value for ICBM use.

2) That's not a rebuttal to my point about the hazard of your small-scale approach. Obtaining resources generally requires big projects. Things like chip fabricators are big projects. Your society can't do big projects very well. Resource collapse, most everyone dies.

What do you not understand about the fact that ICBMs make us less safe, not safer?

What do you not understand about this having zero relationship to the topic of the thread? None of the rocket engines under discussion are in any way suitable for ICBM use; You could as well interrupt a discussion on soldering techniques, with a diatribe about how deadly swords are, on the basis that metallurgy can lead to the making of edged weapons.

Sure they protect us from imaginary incredibly unlikely threats but they increase the threat from human stupidity and animal behavior.

Nobody cares. Start your own thread (in a more suitable forum) if you think anyone will take the slightest interest in debating the bleeding bloody obvious.

 

[lpetrich]

Missile technology has endangered all of humanity.

That's rather off-topic.

Let's get back to discussing the feasibility of different sorts of rocket engines and alternatives like space elevators.

 

[bilby]

Missile technology has endangered all of humanity.

That's rather off-topic.

Let's get back to discussing the feasibility of different sorts of rocket engines and alternatives like space elevators.

Space elevators will be a game changer; but finding materials with high enough tensile strength per unit mass, at a low enough price and high enough volume will be a big ask.

As for suitable sites for the base station, given that it must be on the equator, Singapore seems like the obvious choice, as it's already a major transportation hub. Having said that, the distance of Singapore from the wealthy customers in the USA could make somewhere like Soure, on the Brazilian Atlantic coast a better choice.

 

[lpetrich]

For our planet, space elevators need superstrong cables, stronger than anything that we have been able to make.

Here is a rather hand-waving estimate of how much strength a space-elevator cable will need. It is

P/ρ = v²

where P is the cable's tensile strength, ρ = its density, and v is the surface-satellite orbit velocity of the celestial body where we wish to construct this elevator. It is (escape velocity) / sqrt(2).

For the Earth and the density of water, this means a tensile strength of 63 gigapascals. I checked on some engineering-data sites, and I found that most materials are hopelessly wimpy -- their yield strengths are usually less than 1 GPa, and sometimes much less.

Here are some more numbers. Mars: 13 GPa, the Moon: 2.8 GPa, Ceres: 130 MPa.

If one wishes to use diamond, one must multiply these numbers by 3, for titanium, 4.5, and for steel, 7.8.

Modulus of Elasticity Young's Modulus Strength for Metals - Iron and Steel | Engineers Edge | www.engineersedge.com, Modulus of Elasticity or Young's Modulus - and Tensile Modulus for common Materials -- those two sites also contain oodles of other data.

So space elevators may only be practical for the smaller Solar-System bodies.

 

[lpetrich]

As to cities and places near the equator, I've found:

Galapagos Islands near South America
Quito, Ecuador
Macapá, Brazil. Belém is nearby.
São Tomé and Príncipe islands near Africa
Libreville, Gabon
Entebbe, Uganda, near Kampala
Nairobi, Kenya (a bit off, but the equator goes through nearby Kenyan territory)
Singapore (a bit off, and the equator goes through nearby Indonesia)

So we have several nations that could host a space elevator.

Sri Lanka almost makes it. In his novel The Fountains of Paradise, Arthur C. Clarke moved it southward and used an old name for that place, Taprobane.

 

[untermensche]

Missile technology has endangered all of humanity.

That's rather off-topic.

Let's get back to discussing the feasibility of different sorts of rocket engines and alternatives like space elevators.

I know. I have no obligation to join into masturbatory celebrations of weaponry without a thought to their potentials.

And I can freely give my opinions. Hopefully.

 

[bilby]

Missile technology has endangered all of humanity.

That's rather off-topic.

Let's get back to discussing the feasibility of different sorts of rocket engines and alternatives like space elevators.

I know. I have no obligation to join into masturbatory celebrations of weaponry without a thought to their potentials.

And I can freely give my opinions. Hopefully.

Nobody doubts your desperate desire to give your opinions. It's clearly enough to blind you to the fact that you are the only person in this thread to have said anything about weaponry (other than to ask you to shut the fuck up about them, as they are off-topic).

 

[untermensche]

Talking about missiles is frivolous.

Talking about what they can do is serious.

Launch something from Earth to space. Move something around in space. Now working to return to Earth and land.

What else is there?

 

[bilby]

As to cities and places near the equator, I've found:

Galapagos Islands near South America
Quito, Ecuador
Macapá, Brazil. Belém is nearby.
São Tomé and Príncipe islands near Africa
Libreville, Gabon
Entebbe, Uganda, near Kampala
Nairobi, Kenya (a bit off, but the equator goes through nearby Kenyan territory)
Singapore (a bit off, and the equator goes through nearby Indonesia)

So we have several nations that could host a space elevator.

Sri Lanka almost makes it. In his novel The Fountains of Paradise, Arthur C. Clarke moved it southward and used an old name for that place, Taprobane.

Suitable sites need to have good transport infrastructure to bring in materials for construction, and to bring in passengers and payloads once the thing is running. That means that either you need an established infrastructure (eg Singapore - the engineering effort needed to build an artificial island on the equator itself, at the closest point to Singapore, is trivial compared to the construction of the elevator itself); or somewhere very close to big customers (basically the USA), and on the coast at a site that is suitable for (or already has) a deep water port.

African locations are likely ruled out on both counts; as is the Pacific coast of South America - no really suitable port sites. The Galapagos are too remote; Singapore has to be the front runner IMO.

Of course, suitable material is a much bigger hurdle than site selection. It's probably going to need super-sized mesh molecules - a cable built from strands of macroscopic length (in the order of metres or tens of metres at least, and preferably more like a hundred km). Not something we can do yet; but not something that I would expect to be impossible. If you can make a material mesh long enough in both dimensions to get close to the required tensile strength per unit mass when rolled into a tube, (like Kevlar, but with covalent inter-strand bonding rather than hydrogen bonds) you can probably get sufficiently long monomolecular filaments, and a cable made from such fibre should exceed the required strength - Kevlar is about 5% of the required strength to mass ratio; a twentyfold increase in strength should be doable.

It's just a shame I have no clue how to go about making such long monomolecular mesh based fibres. Graphene might be promising; "all" we need is to make a few million sheets of graphene that are a few hundred kilometres or so on the long side, and at least tens of metres on the short side, roll them up, and spin them into a long rope.

 

[Treedbear]

...
Space elevators will be a game changer; but finding materials with high enough tensile strength per unit mass, at a low enough price and high enough volume will be a big ask.

As for suitable sites for the base station, given that it must be on the equator, Singapore seems like the obvious choice, as it's already a major transportation hub. Having said that, the distance of Singapore from the wealthy customers in the USA could make somewhere like Soure, on the Brazilian Atlantic coast a better choice.

I heard a recent discussion in which the need to avoid lightning strikes was important. They mentioned someplace in the Pacific ocean that has never experienced lightning storms.

Lightning: One possible event that would destroy the elevator cable would be a lightning strike. Lightning has sufficient current and voltage potential in its arc to heat and destroy any composite that we have been considering. One could argue that the carbon nanotubes (melting point ~6000°) would survive a lightning strike and that there may be a similar hightemperature epoxy that could be used for the lower section of the cable. However, we consider this a higher-risk option and believe that there may be a better solution to the problem.

 

[James Brown]

I worry that any and all and all analyses of future beanstalk developments will have to answer the question, "What will happen if someone flies an airplane into it?"

Given that a snapped beanstalk would eventually collapse by wrapping around the entire planet, the potential devastation will forever make it a non-starter.

 

[Treedbear]

I worry that any and all and all analyses of future beanstalk developments will have to answer the question, "What will happen if someone flies an airplane into it?"

Given that a snapped beanstalk would eventually collapse by wrapping around the entire planet, the potential devastation will forever make it a non-starter.

The beanstalk analogy sounds about right. Whatever happened to Jack anyway?

 

[barbos]

Have not heard about lightning strikes being a problem. But airplanes, space junk, meteorites, etc make this whole idea pretty unworkable.