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October 06, 2011

Floating airship could radically reduce the cost of space accesss

A radical concept to use airships to bring cargo into space has the potential to dramatically reduce the cost of putting payload into Low Earth Orbit (LEO). The concept eschews chemical rockets in favor of a series of floating airships. Aerospace engineer John Powell has studied this idea since 1979, and in 2008 published floating to space , describing the paradigm in detail. In an interview with Sander Olson, Mr. Powell discusses how his company, JP Aerospace , is actively developing the technologies and capabilities to bring this concept to fruition. Powell believes that with sufficient development and scaleup, the cost of delivering payload to orbit could drop to as low as a dollar per pound within twenty years.
A 10 page presentation on the concept

John Powell
Question: What is the airship to orbit program, and how long has it been active?
The airship to orbit program has been going on since 1979. The basic idea consists of having an airship, a floating platform permanently moored at 140,000 feet, and another orbital airship that would travel from 140,000 feet to orbit and back. With a propulsion engine and an aerodynamic shape, such a craft could reach orbit. The ascent to orbit would be measured in days, but eventually orbital velocity should be reached. When we first began researching this concept, there were about 10 potential showstoppers to this concept, and now we are down to about 3 remaining potential showstoppers.

The 3 remaining potential showstoppers:

1. Scaling active drag reduction.
Active hypersonic drag reduction has been demonstrated in the lab for 30 years. Can we take it out in the real world and scale it up to the airship to orbit requirement?

2. Power density.
Can we achieve the necessary electrical power to mass ratio? The current trend in industry says it will happen in 5 to 7 years, but it's out of our hands.

3. Can you really build two mile long lightweight structures at the edge of space? Working on it, we will let you know.






Question: So a single airship going from the ground to orbit isn't feasible?
An airship that is sufficiently light and thin would not be able to survive the winds at lower altitude. So we have the first craft travel to a floating station, which is permanently anchored at 140,000 feet. This craft would be helium powered, and take a couple of hours to reach the station. Then it unloads its payload/crew, and returns to the ground.
Question: Wouldn't a combination of hydrogen with flame-retardant materials be more cost-effective?
Hydrogen is about one-fifth the cost of helium, and gives slightly better performance. But working with hydrogen requires permits for everything. Due to much larger insurance costs and permit costs, it actually turns out that using helium is cheaper than hydrogen. Helium is somewhat scarce, but it is actually an artificial scarcity - helium is vented in the U.S. in order to keep the price up.
Question: So this floating station would need to be quite large.
Yes, this would be a large port which we call a "dark sky" platform. In the fall of 2013 we plan on having the first manned dark sky station tested. When perfected, these stations will be the place that the large airships to orbit would be constructed, and would dock. The dark sky stations would be about 2 miles across, and weigh thousands of tons. It would have gaseous hydrogen in cylinders or "arms" protruding from the station.
Question: For the airship going to orbit, would the engines be chemical, ion, or some sort of hybrid?
The engines would be a hybrid, employing both ion thrusters and chemical propulsion. At certain points we will be using ion thrust, and at other points we will be using chemical. There is a tradeoff between efficiency and time to orbit, the more efficient you are, the longer it takes to achieve orbital velocity. Rockets are measured in terms of specific impulse, which provides an indication of the efficiency of the system, with higher being better. The specific impulse of our hybrid is about 1100, which compares to about 450 for chemical rockets and 30,000 for ion thrusters. So this hybrid can either be viewed as being the most efficient chemical rocket ever, or the least efficient ion rocket.
Question: So this rocket is half ion and half chemical?
Yes, it is almost always half and half. The final insertion is all chemical. The chemical rocket will use wax/nitrous oxide. That is what we are currently testing. With sufficient R&D, I am confident that we could get a hybrid engine up to 2,000 specific impulse. That would obviously have a beneficial effect on payload capacity, perhaps as much as a quarter increase in payload.
Question: How much payload could be brought up with each airship?
With the hybrid engines, we are looking at 15 tons of payload. But our airships would be both pressurized and crewed, so this payload could be astronauts, scientists, or tourists. All of our tests so far have been unmanned, but we plan on commencing manned flights next year, and we plan on having all operational flights manned.
Question: Would this system employ solar power?
Battery performance has dramatically improved during the past several decades. So for ascents lasting days, it actually makes more sense to remove the solar voltaics, and to replace them with straight batteries or fuel cells. We convert chemical energy from the rocket engines to electric energy. So we can actually extract power from the chemical engine.
Question: What sort of preliminary vehicles are you building?
We have built a series of vehicles, each larger than the last. We are currently building a ballistic vehicle that could go to an altitude of 60 miles from a smaller "dark sky" station. We have a specific plan of testing progressively larger and more sophisticated vehicles every year or so, culminating in full-sized prototypes.
Question: How far are you from testing this vehicle?
We are about five years from testing the 60 mile airship. Within five years of that, we could see a fully orbital vehicle developed. The beauty of this system is that the reentry process would be so slow that virtually no heat would be produced. The system begins to decelerate as soon as the engines are turned off. So we don't have to develop any heat-shielding system.
Question: How many crew would travel with each airship to orbit?
We envision perhaps four crew. The advantage of this approach is that the ship can be repaired on route. So if a main engine failure occurred, a crew could repair the engine within a couple of hours, and the flight would then continue. That is one of the main advantages of this system - repairs could be made inflight, without needing to cancel the flight.
Question: In an emergency, how would a sick/injured crew be able to quickly land?
A pod, similar to the NASA Apollo capsule, would be attached to the craft going to orbit. It would have a heat shield to deal with the heat of reentry. An identical craft lacking a heat shield would be attached to the floating platform. Although this approach would add several tons of weight to the craft, it would allow the vehicle to operate safely.
Question: Given the weight penalty of these manned craft, wouldn't unmanned vehicles be more cost-effective?
Unmanned craft would be able to place more payload into orbit, but our focus has always been on putting people into space. Moreover, having a manned system greatly adds to the flexibility of the system. Current aircraft and cargo ships are highly computerized with sophisticated autopilots. But these vehicles still have captains and other crew. There is a good reason for this - the flexibility of manned craft more than compensates for any weight penalty.
Question: Why is the telecom industry interested in your floating stations?
It is much cheaper to put a transponder on our floating platform than on a satellite. The transponder is the device that actually beams that signals in satellites. Moreover, transponders can be easily replaced if they fail. So the dark sky stations will all have transponders aboard, perhaps along with other telecom equipment. This would be an additional source of revenue.
Question: Most of your flights generate revenue. How do you do this?
We have had 17 flights so far this year, and all of our flights are self-funded and pay for themselves. We have a variety of ways in which we generate revenue. Our balloons have ads on them, so they look like nascars. We have had deals with telecom manufacturers, and with cellphone operators. We make deals with aerospace corporations such as Lockheed to test components. We don't need to take any outside investment or grants.
Question: Could these floating dark sky stations be used for tourism?
Yes, we think that these stations would be ideally suited for tourism. In order to be economically viable, it will need to be a dual-use facility. These stations could have restaurants and hotels, they will have satellite transponders, and they will host research facilities as well. We are building a series of dark sky stations, each one larger than the last, and the final one should be about 2 miles in diameter.
Question: When will you have your first manned flights?
We plan on having our first manned flights by 2013. The flights will go to 100,000 feet, and the total flight duration would be 3-4 hours. There will be a six mission test program, before the next vehicle gets built. Due to budgetary limitations, we tear down our current vehicles to get the materials to make the next vehicles. We are forced by economic realities to be extremely efficient in our operations.
Question: Are you seeking any outside investments or funding?
We aren't seeking outside investments. We get more financing by doing more work. For instance, we've done work for Lockheed - we have flown equipment for Lockheed, which needed instrumentation tested to 100,000 feet. We did two runs of the payload for them. In 2011 we have done seventeen runs to 100,000 feet, and we may be doing twelve more. So we have no shortage of paying customers.
Question: Do you send any payloads up for free?
Yes, we are actively using this scheme to encourage interest in science among kids. We do "pongsat" missions, where we fly ping pong balls for free. These balls are cut in half, and schoolchildren put experiments in these balls. This year, we have several missions where we carry hundreds of ping pong balls, each with an experiment in it. Some of these balls are actually quite sophisticated. An entire first grade class flew gummy bears - this is a great way to get kids interested in science. We also fly payloads from Universities.
Question: What is the estimated cost per pound to Low Earth Orbit (LEO), once this system is perfected and scaled-up?
I think that the costs could eventually go as low as a dollar per pound to LEO. This could happen in as little as twenty years. We could get down to $100 per pound within a decade. Costs will be directly related to commerce and achieving economies of scale.
Question: A number of formidable technical challenges would have to be surmounted in order to make this concept feasible. For instance, how will you be able to create a gossamer airship that is capable of withstanding supersonic flight?
Many in the industry have dismissed this idea as crazy. But in the 1960s, they flew high altitude weather balloons at Mach 10, so we know that the idea is possible. At these heights, there is almost no atmosphere to cause friction. But there are also other potential showstoppers to this concept. We will need much better power sources and batteries, in order to power the engines. We will also need to employ some very light but extremely durable materials in the gossamer airship, so it doesn't break up going mach 20.
Question: What would you like to see JP Aerospace doing by 2021?
By 2021 we should have full-scale dark sky platforms hovering permanently at 140,000 feet. These stations will support tourism, telecom equipment, and a docking port for the orbital airships. Every week and a half, another ship goes into orbit. Hundreds of tons of payload per year would be going into orbit. Some flights would be cargo, other flights would be passengers, and there would still be a mix. I could even see humans colonizing the upper atmosphere using this method.







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