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In the other thread we were discussing using suborbital (or even sub-suborbital) hops to Everest and other places using the technology SpaceX is developing for its Falcon 9R.
My question is: Can we think of applications for technologies like liquid rockets other than space launch? If we could, that would be a great boon to the launch industry because it would mean more return on investment for technological development and potentially development and testing in other sectors.
So: Liquid rockets for Earth. What uses could they have?
-Josh
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One that springs to mind is rapid package delivery. The delta-V to go from New York to Los Angeles (4000 km) is 6.5 km/s if done as one hop (13 km/s if you use rockets to slow down), but could also be done in two smaller hops of 4.5 km/s (9 km/s), or four hops of 3.5 km/s (7 km/s). One hop would have a travel time of 900 s, 15 minutes. Two hops would involve 1300 s spent in transit, about 21 minutes. Four hops would be about 1800 s spent in transit, about 30 minutes. Either way, if there were cargo that had to arrive as close to immediately as possible sending it by rocket might be feasible.
Then there's also the potential for the use of liquid rocket engines as blowtorches on a massive scale. One could imagine a rocket with significant amounts of extra hydrogen burning its way through iron rich rock by smelting it.
-Josh
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One that springs to mind is rapid package delivery. The delta-V to go from New York to Los Angeles (4000 km) is 6.5 km/s if done as one hop (13 km/s if you use rockets to slow down), but could also be done in two smaller hops of 4.5 km/s (9 km/s), or four hops of 3.5 km/s (7 km/s). One hop would have a travel time of 900 s, 15 minutes. Two hops would involve 1300 s spent in transit, about 21 minutes. Four hops would be about 1800 s spent in transit, about 30 minutes. Either way, if there were cargo that had to arrive as close to immediately as possible sending it by rocket might be feasible.
I think no state would accept foreiner rockets in their air space, because may be impossible to distinguish a speed cargo or passengers rocket from a militry rocket armed with nuclear warhead.
Then there's also the potential for the use of liquid rocket engines as blowtorches on a massive scale. One could imagine a rocket with significant amounts of extra hydrogen burning its way through iron rich rock by smelting it.
This may be interesting: we can image some special launchpad, where the exaust of the rockets is channeled over something to melt.
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A cargo ship could also deliver a nuclear warhead to a coastal city, and most large cities are on the coast. Most cargo ships aren't intercepted prior to entering a city. Customs agents show up to inspect the cargo, and the button is pressed, the city goes up in a mushroom cloud. Rockets aren't the only way to deliver nuclear warhead, and nuclear warheads aren't the only thing rockets can deliver.
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I'm with Tom on this one, actually. If your nuclear warhead were small enough it would be fairly trivial to smuggle it into any city with, for example, a truck.
Beyond that, New York and Los Angeles are both American cities. Likewise I would expect that there wouldn't be an issue for any European cities within the Shengen Zone.
I was thinking that smelting would be the only use of the rocket engine. This would mean that the thrust beverages would be a negative rather than a positive. I suppose this would make it more of a large blow torch.
-Josh
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I'm with Tom on this one, actually. If your nuclear warhead were small enough it would be fairly trivial to smuggle it into any city with, for example, a truck.
Beyond that, New York and Los Angeles are both American cities. Likewise I would expect that there wouldn't be an issue for any European cities within the Shengen Zone.
I was thinking that smelting would be the only use of the rocket engine. This would mean that the thrust beverages would be a negative rather than a positive. I suppose this would make it more of a large blow torch.
It's true (and may be interesting to note how useful can be spending a lot of money in anti missile defence, when a nuke can be delivered on an anonymous cargo ship, but this is another story) but what worths is not reality but perception of reality. In people mind, rocket is more and more impressive than a cargo ship.
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Ok, going to be devil's advocate. Rescue from Mount Everest has to be set up well in advance. Building something that takes several years, while those in trouble can't breathe? If you're going to set up rescue, they why use Falcon 9R? As was pointed out, airliners can fly at or above the altitute of Everest. Helicopters can't. Why not build a VTOL aircraft similar to a Harrier or F-35, but designed for rescue and with an engine specifically designed to land vertically on Everest? A V-22 Osprey has oversized propellers, with swash plate so they act as helicopter blades. But why not use VTOL jet technology for something the size of an Osprey?
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Why not seed the flow of a rocket engine with something like salt that ionizes easily, then capture the KE of the stream down to the recombination point with an MHD generator. Then shock-down the decelerated stream to subsonic, and put it through a heat exchanger to generate steam for a turbine-driven generator. That's two DC sources of two voltages, but we ought to be able to do something with that. Might be as easy as simple seawater injection.
As for rescue atop Mount Everest, the design of a VTOL aircraft or helo for operation there is simply a matter of design for low density. It just takes a bigger prop, wing, and engine for the load. Just because no one has yet done it, does not mean it is impossible. The density ratio to SL std at 29 kft is 0.3887. Harsh but not impossible. The real problem for any aerial rescue craft on Everest is suitable touchdown sites. There are none. Coming up with a way to glom onto ice and rock at impossible angles is the true design problem. In comparison, flying an aircraft there VTOL is quite easy. Just not cheap, not ever.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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https://en.wikipedia.org/wiki/Project_Hot_Eagle
However, you don't have to restrict it to Marines. Perhaps we could build single stage rocket powered VTOL aircraft that are large enough to contain a hospital. A disaster happens, and within an hour there is full medical help available. The shelters can be brought with the Ekranoplans, they're less time critical.
What rockets excel at is going fast. Not much more. If you're looking at applications for them, you need to look at time critical situations.
"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony
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I see the danger in allowing nations that are not looking to use a rocket for a peaceful purpose which could cause issues for bordering nations but we have that now its the much larger hop that is of great concern for those particular nations or groups that might get a hold of that technology.
We did discuss the repurposing of engine for mars in the now gone thread Loius would remeber these as Foot hold and Toe Hold topics which got into the incremnental steps of colony growth and to what was needed to make growth possible. The idea of using a thruster for a furnace was one idea to help with early pig iron creation for use as well as glass making.
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No argument from me with regards to Everest. The idea is sort of a red herring, insofar as it sounds like something that could be practical until you look into it more closely. This is especially true because the areas where a climber would be most likely to be injured are those where it would be most difficult to land.
Some kind of VTOL (Vertical TakeOff and Landing) plane would make more sense for a journey to the top. It's not inconceivable that this could have liquid rocket components to aid with takeoff and landing on what would be, in effect, a helipad.
Even small planes, like the Cessna Citation Mustang have service ceilings more than 3 km above the top of Everest.
For that matter, there are already VTOL planes with service ceilings higher than Everest. See, for example, the Bell XV-15, with a service ceiling a couple hundred meters higher than Everest. It might not be able to take off at that height, but certainly it puts rockets out of the main propulsion system.
I also agree that from a transportation standpoint rockets are best at going fast. They are not fuel efficient, and there's nothing on Earth too high for other forms of transportation to reach.
Well, they're also really good at producing a lot of power. The mechanical (exhaust) power-to-mass ratio of the Space Shuttle Main Engine (operating in Vacuum) was 1.6 MW/kg. That is simply unbeatable. Efficiency is pretty good, too. Again operating in vacuum, the efficiency is 62% based on the higher heating value of Hydrogen. Comparable figures for the Merlin 1D used in the Falcon 9 are 2.2 MW/kg and 32%, which I suspect is probably an incorrect value but can't figure out why.
Use in power plants sounds like a good one, then, though I think it's pretty legitimate to ask if you're burning kerosene in air and are going to need to pressurize what the difference really is between that and turbines as they currently operate in power plants.
-Josh
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Rocket MHD might never make sense as an electric power plant here on Earth. Simple fuel-fired boilers will likely continue to be less expensive and more reliable for power generation. They have been, for the last half a century. I first saw rocket MHD mentioned in a propulsion textbook from the 1960's. But, the idea might have real merit off-Earth, where an oxidizing atmosphere is unavailable to run the normal furnace and boiler rig. As far as I know, no one has looked at this in a very long time.
The notion that rockets excel at speed is quite correct. Personally, I am a disbeliever in high supersonic-to-hypersonic cruising aircraft in Earth's atmosphere. The heating and the drag are just overwhelming technically and financially. It's OK for missiles. But for manned aircraft, exoatmospheric skip-glide makes a lot more sense for suborbital travel. If this were to become some sort of civil travel similar to airlines, it would be fairly easy by communications to ensure that such craft are not mistaken for missile attacks.
Whether that or suborbital ballistic is more financially feasible is an open question. Both will be a lot more expensive than subsonic transport aircraft, but for some applications where time really is money, the much faster speed could pay off. Going exoatmospheric is how you avoid the heating and the drag over most of your trajectory. There is a hypersonic entry heating transient at every dip back into the atmosphere, but the point is, it's a short transient. The ascent heating is similar, but usually much less severe.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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The question, as usual, is the Delta-V required to make this work. If it's anywhere close to the delta-V required to make orbit, chances are it's going to be equivalently expensive. SpaceX plans to sell seats on Dragon for $20,000,000. I find it hard to believe that anyone would be willing to pay that much for a ride to anywhere on Earth, even if you can get from New York to Beijing in five minutes.
-Josh
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For a ballistic suborbital flight, the delta-vee is about like that of an ICBM for halfway-around-the-world. That would be something like 5.3 km/s as you leave the sensible air, at something near a 45-degree path angle. That's uncorrected for gravity and drag losses. In comparison, the uncorrected orbit speed is near 7.7 km/s.
For skip glide, you only need about Mach 3 to 5 as you leave the sensible air, but you will need it a bunch of times to go halfway around the world. Your path angle will be quite shallow, and your apogee just barely exoatmospheric. This isn't launch rocket stuff, this is airplane-that-goes-ballistic for a few hundred miles a jump. Apples and oranges, doesn't compare on delta-vee. Sorry, I have no data for such a vehicle.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Sure. Mach 4 is about 1350 m/s. If you leave the atmosphere at a 15 degree angle you'll travel about 100 km per skip. If you need to add 25% of your delta-V back per skip that's about 350 m/s for every hundred km over 100 km, or 1100 m/s plus 350 m/s for every 100 km. Going halfway around the world that works out to be a whole lot of delta-V.
-Josh
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Interesting to think of making use of the engine to create power in a closed chamber, would this be analogis to a steam plant in function. So the exhaust would be recirculated directly back into the sabetiier reactor to make more methane, water and oxygen for later use.
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