I know that JP Aerospace doesn't seem to make much headway with their "airship to orbit" concept.
Still, I wondered whether their concept of a stratospheric station (based approximately 140,000 feet above sea level or about 40km up) would be an interesting addition to the sub-orbital "space"travel crowd. Yes, it is technically not in space and no, there is no weightlessness involved, but the view would be quite stunning and could be enjoyed for some time, not just a few minutes.
Day trips or one-night stay-over trips up there including "dinner with a view" could be an interesting (cheap?) alternative to the 250k 6 minute joyrides with Virgin Galactic.
Quote from: AlexCam on 08/07/2011 01:33 pmI know that JP Aerospace doesn't seem to make much headway with their "airship to orbit" concept. A huge surprise QuoteStill, I wondered whether their concept of a stratospheric station (based approximately 140,000 feet above sea level or about 40km up) would be an interesting addition to the sub-orbital "space"travel crowd. Yes, it is technically not in space and no, there is no weightlessness involved, but the view would be quite stunning and could be enjoyed for some time, not just a few minutes.If you could make such a station, it would also be quite attractive for astronomy and cosmic ray research. Depending on location, it could also serve as a communication relay. Depending on how your transport worked, you could also get quit a bit of free-fall on the way down. For the adventurous, you could offer the option of jumping But building something with such a large payload and indefinite life at that altitude appears quite challenging. Especially if you want to maintain it at a relatively fixed location.QuoteDay trips or one-night stay-over trips up there including "dinner with a view" could be an interesting (cheap?) alternative to the 250k 6 minute joyrides with Virgin Galactic.6 minutes is the zero G time, the whole flight is a bit longer, and both the powered portion and reentry should be quite thrilling in their own right.Edit:There has been some successful work done with long duration high altitude balloons with fairly significant payload, e.g. http://www.csbf.nasa.gov/balloons.htmlHowever, these are at the mercy of the wind, and the payloads are still small in comparison to what is being discussed here.
I tend to think that lighter than water "vehicles" could go the fastest- they seem to me to be the easiest to get to 300 mph or faster. Or for a few thousand dollars or less, a lighter than water vehicle could "achieve this record speed" with what I tend think as less trouble than a lighter than air vehicle could do it.
QuoteI tend to think that lighter than water "vehicles" could go the fastest- they seem to me to be the easiest to get to 300 mph or faster. Or for a few thousand dollars or less, a lighter than water vehicle could "achieve this record speed" with what I tend think as less trouble than a lighter than air vehicle could do it.I can't find a link but there was a proposal for a positive buoyancy submarine or bottom launched torpedo that would "fly" up to attack surface ships with only its buoyancy and hydrodynamics to get pretty good lateral speed, from memory 30knots(??), a few years ago that I read about it, its big advantage was its stealthiness.
Guy with balloon wants to do "near-space" tourism:http://www.wired.com/autopia/2011/08/inbloon/
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.
Just found this thread.Quote from: AlexCam on 08/07/2011 01:33 pmI know that JP Aerospace doesn't seem to make much headway with their "airship to orbit" concept. Yes it's hard to see progress as they do a lot of testing on such a small scale (and it is a 30 year programme that they're only a bit over halfway through!).Things are due to get a bit larger scale in the relatively near future. They're hoping to fly their scale 90 foot Ascender by the end of this year: http://jpaerospace.com/blog/?p=5147
The JP crowd seems to be in denial about basic physics. You simply cannot have lift from the atmosphere without also having drag, whether that lift comes from buoyancy or aerodynamics.Go up where the atmosphere is thin and you can have lower drag, but that means lower lift from buoyancy or aerodynamics. If you add a large surface area, you can get back lift, but drag comes right back along with it. It's those same gas molecules bouncing off your craft that give both lift and drag.
Quote from: ChrisWilson68 on 06/18/2013 09:24 amThe JP crowd seems to be in denial about basic physics. You simply cannot have lift from the atmosphere without also having drag, whether that lift comes from buoyancy or aerodynamics.Go up where the atmosphere is thin and you can have lower drag, but that means lower lift from buoyancy or aerodynamics. If you add a large surface area, you can get back lift, but drag comes right back along with it. It's those same gas molecules bouncing off your craft that give both lift and drag.Who said otherwise?
Anyone who takes the airship-to-orbit concept seriously says otherwise. The ion engines that gradually accelerate the airship to orbit are supposed to overcome drag through high mach numbers while gravity is being countered by a combination of buoyancy and aerodynamic lift.
[I'm sorry, but your point is still alluding me. Rocket engines regularly provide sufficient thrust to overcome drag.. that's kinda what they're for.
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?[...]
Quote from: ChrisWilson68 on 06/18/2013 11:37 amAnyone who takes the airship-to-orbit concept seriously says otherwise. The ion engines that gradually accelerate the airship to orbit are supposed to overcome drag through high mach numbers while gravity is being countered by a combination of buoyancy and aerodynamic lift.I'm sorry, but your point is still alluding me. Rocket engines regularly provide sufficient thrust to overcome drag.. that's kinda what they're for.
Yes, and the rocket engines have to expend some of their thrust to overcome gravity losses. For that reason, high thrust is needed -- they need to quickly ramp up to orbital speed because every second along the way they're expending energy fighting gravity.The benefit of the airship-to-orbit concept is supposed to be that a combination of buoyancy and aerodynamic lift counter most of the gravity loss so the engines can use low-thrust, high efficiency engines, such as ion thrusters.My point is that if the airships are fighting gravity with buoyancy and/or aerodynamic lift, they will inevitably have much, much higher drag than today's launchers, which go up out of most of the atmosphere to avoid drag before picking up most of their speed.
However, I still don't think it can possibly work. Even if they have more than 15 metric tons to work with, it probably isn't enough.
And I severely doubt ion engines can give enough thrust to deal with the drag on a vehicle that size even at that altitude.
And can it possibly deal with the heating induced by moving at near orbital velocities even through that sparse atmosphere? It can't really have any kind of shielding at all, given the weight constraints...
Quote from: ChrisWilson68 on 06/18/2013 09:43 pmYes, and the rocket engines have to expend some of their thrust to overcome gravity losses. For that reason, high thrust is needed -- they need to quickly ramp up to orbital speed because every second along the way they're expending energy fighting gravity.The benefit of the airship-to-orbit concept is supposed to be that a combination of buoyancy and aerodynamic lift counter most of the gravity loss so the engines can use low-thrust, high efficiency engines, such as ion thrusters.My point is that if the airships are fighting gravity with buoyancy and/or aerodynamic lift, they will inevitably have much, much higher drag than today's launchers, which go up out of most of the atmosphere to avoid drag before picking up most of their speed.Yep, it's definitely a tradeoff. JP seems to think that's a workable tradeoff, but he doesn't show his work (or hasn't even figured out how to work it yet) so we can't evaluate whether or not his solution will work.That's a far cry from your original claim of being "in denial about basic physics".
QuoteAnd I severely doubt ion engines can give enough thrust to deal with the drag on a vehicle that size even at that altitude.Who said anything about ion engines?
The third part of the architecture is an airship/dynamic vehicle that flies directly to orbit. In order to utilize the fewmolecules of gas at extreme altitudes, this craft is big. The initial test vehicle is 6,000 feet (over a mile) long. Theairship uses buoyancy to climb to 200,000 feet. From there it uses electric propulsion to slowly accelerate.
QuoteAnd can it possibly deal with the heating induced by moving at near orbital velocities even through that sparse atmosphere? It can't really have any kind of shielding at all, given the weight constraints...Now you're asking a question that someone could actually answer.. has there been any big hypersonic Mylar balloons flown in the upper atmosphere? Well yeah, with significant challenges overcome.. http://history.nasa.gov/SP-4308/ch6.htmThat doesn't mean JP Aerospace can do it, but nothing will.. until they do it.
I think all the points about ion engines apply to any low-thrust electric engine.
The link you gave is about project Echo. That was an inflatable satellite system. It was launched deflated and only inflated once in orbit, and out of essentially all atmospheric drag. That's not really a hypersonic balloon.
I stand by my claim that they're in denial of basic physics.
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.
Quote from: ChrisWilson68 on 06/19/2013 05:14 amI think all the points about ion engines apply to any low-thrust electric engine.Not at all.. ever heard of plasma thrusters?
QuoteThe link you gave is about project Echo. That was an inflatable satellite system. It was launched deflated and only inflated once in orbit, and out of essentially all atmospheric drag. That's not really a hypersonic balloon.You actually have to read the link.. there was a whole test program which involved deployments in the upper atmosphere.
Quote from: ChrisWilson68 on 06/19/2013 04:59 amI stand by my claim that they're in denial of basic physics.Lots of people said that about JPA's claim that they could use propellers at 100k ft altitudes. Then they demonstrated propellers working at c 100k ft! Of course they don't break the laws of physics, people had misunderstood/mis-applied their knowledge to what JPA were doing.
There are plenty of crackpots who propose perpetual motion machnes etc. But given what they've achieved I give JPA a lot of credit that they're not crackpots. They clearly understand about drag and are not in denial about it. They may be wrong about whether they can get the technology to work, or even if the technology in principle gives them the drag reductions they need, but it seems pretty unlikely to me that they've missed a basic physics gotcha.
And the fact that someone else was wrong in criticizing claim A really has no logical bearing on my criticism of claim B.
Quote from: ChrisWilson68 on 06/19/2013 06:14 amAnd the fact that someone else was wrong in criticizing claim A really has no logical bearing on my criticism of claim B. It does when criticisms of both claim A and claim B imply the same claim C (that JPA don't understand basic physics). I was giving counter evidence to claim C. As I'm sure you're aware, by the law of logic known as the contra-positive that means criticisms of both claims A & B are invalid. :)
Plasma thrusters are a subset of ion thrusters.
All the balloon deployments mentioned in the link involved first putting the balloon into orbit, then inflating it.
You think they have a secret technology that they won't tell anyone about and have never demonstrated to anyone that would re-write every basic textbook on drag? Good luck with that.
Quote from: ChrisWilson68 on 06/19/2013 05:59 amPlasma thrusters are a subset of ion thrusters.No they're not. Plasma is not ions, by definition.
Actually, plasma is ions, mixed in with electrons. Turning a gas into a plasma is called "ionizing" it.The Wikipedia entry for "Plasma propulsion engine" starts with "A plasma propulsion engine is a type of Ion thruster..."
Seeing as you're disinterested in actually reading what was linked, can you please stop commenting on it like you have?
.. and five more flights. Including a completely successful deployment.
... the Shotput tests, whose ABL X248 carried the test balloons only to 200 to 250 miles above the surface ...
http://nextbigfuture.com/2011/10/floating-airship-could-radically-reduce.htmlQuoteQuestion: 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.
Inside the tail of the new Ascender
Putting away the port Ascender envelope at the end of the day.