I haven’t run the numbers on this yet, but I was thinking about how to do reusable transportation on Venus recently. My previous Venusian Rocket Floaties blog post showed that existing upper stages, sealed off, could float at altitudes high enough not to melt their seals (though still roasty-toasty). My thought was that you could drop down to that altitude, deploy a balloon, and float back up to a safe altitude for recovery by another vehicle. But I got thinking about the reliability and risks of that approach, and it gave me a crazier idea (which as I said above I haven’t run the numbers on yet):
What if you designed a rocket with one of its tanks (the fuel most likely) actually a balloon with the fuel in gas form? Make the balloon big enough so that when the propellant tank is “empty” (and just some sort of buffer gas is in there to fill it), the whole stage is buoyant at a safe altitude. Leave the engine and oxidizer tanks at the bottom “normal”, but have a big balloon tank attached to them via some sort of truss structure.
Some considerations:
- You’d most likely have to attach payloads to the side not the top of the balloon because you probably want the balloon at as low a pressure as possible when it reaches orbit.
- However you’d want it at around 1atm pressure of something when you come back in, so it won’t collapse at the 1atm pressure level.
- You’d have to parallel stage bimese style instead of the more traditional vertical stacking you do on earth, for similar reasons to those mentioned above.
- While a spherical balloon would be most mass efficient, to keep air drag down you’d probably want a cylindrical balloon.
- It might be best to pick a fuel gas that liquifies when chilled (methane or propane?). Then you could theoretically have a fan pull gas from the balloon, and run it through a heat exchanger with the LOX to liquify it before running it into the engine?
- Likewise, you probably want the gas in the balloon on reentry to be something light like GH2 or GHe…not sure the best way to transition between the fuel filling the balloon and this filling the balloon. Could be something carried in an onboard reinflation tank, or it could be something you do at an orbiting station?
- Due to the very large diameter you could get even with a cylindrical real ballon tank, I wonder if you could use that large diameter to wrap a fixed MAC coil around for both initial aerocapture, and maybe magnetoshell assisted aeroentry. Could you get the velocity low enough that your balloon can take the remaining heating without any special TPS on it?
- You probably don’t want to make the thing have to float when fully-fueled–you probably want the carrier blimp to support it until it is launched. That way your balloon volume is determined by the mass of the system at recovery, and you just fill the balloon to whatever density of fuel gas makes the most sense to provide the right amount of fuel for the stage.
I won’t have time to run the numbers on this for a week or more, but I wanted to toss this out there. It’s crazy, but if you could pull it off, it would enable fully-reusable Venus rockets with passively safe recovery. You’d still need a carrier vehicle to come out and fetch it, much like ocean recovery of capsules, but without flat, non-moving platforms to land on, this may be the best way of doing things.
Jonathan Goff
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Balloons are fine, but lots of good stuff is on venus and too hot to get to?
Cylinder: 10 meter diameter
With cone on top: 10 meters to 5 meters and height 5 meters.
Length 80 meters.
Or 32.8 feet in diameter and 196.85 feet long- plus cone: 16.4 feet.
Total length: 213.25 feet high.
–Saturn V: “The Saturn V rocket was 111 meters (363 feet) tall” and
33.0 feet (10.1 m) in diameter–
So it would be big but empty a balloon.
The 80 meter section will be two sections.
The bottom 30 meter section will have cylinder wall thickness of
1/8″ and top top 50 meter section and cone will 1/16″ thick walls.
Structure made of high strength aluminium [40,000 str yield].
And bulkhead between 30 meter and 50 meter section with pump
and plumbing to transfer gases between the tanks.
Total displacement:
10 meter diameter and 80 meters length: 6280 cubic meters.
cone: 523.3 – 65.41 is 457.89
Totals: 6737.89 cubic meters
Or if atmosphere is 1.2 kg per cubic, displacement weight is
8085.468 kg.
10 diameter 50 meter long at 1/16″ [0.0015875 meters] walls is
2.492375 cubic meters of aluminium, weighing 6729.41 kg.
10 diameter 30 meter long at 1/8″ [0.003175 meters] wall is
2.99085 cubic meters of aluminium, weighing 8075.29 kg
And will appro cone as same as 10 meter diameter and length cylinder:
Or 1/5th of 50 meter cylinder: 1345.88 kg
Totals: 6729.41 + 8075.29 + 1345.88 kg is: 16,150.582 kg
Or if filled with hydrogen gas, it would weigh over 8 tonnes on Earth.
Or if air density was more than twice 1.2 kg per cubic meter it could
float.
The 10 meter [393.701″] outside diameter with 1/16″ thick walls have str yeild
of 12.7 psig.
And with 1/8″ 25.4 psig
On Venus: at 40 km the air temperature is 418 K and air density of 4.404 kg per cubic
meter with pressure at 3.501 atm-
http://selenianboondocks.com/2013/11/venusian-rocket-floaties/
3.501 atm is 51.4647 psi
So if at 40 km both cylinders needs more than 51.4647 psi at 418 K. And top one probably
should around about 4-5 psi higher, and lower one could be as high as about 15 psig.
So how tonnes of hydrogen is needed?
So at around 20 C and 1 Atm, oh here:
“0.08988 g/L (at 0 °C, 101.325 kPa)”- google
So at 273 K and 1 atm it’s 0.08988 g/L, or 0.08988 kg per cubic meter.
In increase temperature to 418 K- so 273 + 145 K that is about 50% increase in temperature.
Doubling temperature doubles pressure- or 1/2 volume. Or 35 psi at 0 C is 52 psi at 418 K.
14.7 psi increased to 35 is 20.3 psi. So say 2.5 times 0.08988 is .2247 kg per cubic meter.
Need 6737.89 cubic meters: 1514 kg. That’s the least, so say 2 or 3 tonnes.
So got more than twice 1.2 kg at 40 km of Venus:
4.404 times 6737.89 is 29673.66
29673.66 – 16,150.582 is 11523 kg
Plus the 2 tons of hydrogen and 1 ton of other stuff.
about 8000 kg could land on it, and it would sink to 40 K and float.
Or massive loads cause it to sink lower.
Before landing anything one want to increase amount pressure [mainly in upper
tank to highest safe level as when sink you don’t want less pressure in the tank
as in the atmosphere. Likewise when it rises you want reduce pressure so the don’t
explode or are damaged by over pressurizing relative to Venus pressure.
Because it’s size and relative lightness, other than ablative issues, it should be
fairly easy to get from orbit to the atmosphere, and because of it’s low terminal
velocity in the atmosphere, and d weighed at one end, it should “land” easy enough.
But in terms accelerating rockets to orbit, has problem due to changing pressure.
Or basically it would need to be bigger and taller. And or other modifications.
And probably most would consider this one too big.
Some notes regarding Venus.
Comparing large scale terraforming, it seems to me Venus is easier than Mars.
Though I am not fan of large scale terraforming- not fan of any kind of massive
governmental controlled project- I am not fan of a totalitarian anything regardless
of the noble desires involved.
And small scale terraforming of Mars or Venus is quite doable. Or if have market for
water in space, one will probably easily terraform either and at modest costs. Terraforming for a future a 1000 years in the future are stupid. Especially if combine something for 1000 years in future and present costs in range of trillion dollars a year. Even a billion of dollar year, though rather insignificant in terms of damage to humanity in general- it’s still stupid- and waste of anyone life who embarks upon it.
But if get a water market in space, this will lead to asteroid mining, and ability to move space rocks- and if wanted [not clear if it’s wanted] one make sunshade at Venus L-1 from dust. Or make the sun appear red from Venus orbit. Of course that is slow process. But if that is wanted, one could add to the project the addition of water to Venus. It seems to lacks water, anyhow- or if take all water out of the Venus atmosphere it only makes very small ocean- and combine with bone dry surface, it wouldn’t even dampen the surface very much. Or the water which apparently at Venus makes Mars seem overly abundant in water [not counting the factor, that I consider it quite possible Mars is wetter than we currently generally assume or say it is]. Now, there available in our solar system many Earth oceans of water, but thinking on scale of less 1/10th of earth oceans. So Venus isn’t as dry. So say 5 times more water in Venus atmosphere then it’s already has.
But regardless of what one do, still not much fan of even more reasonable global changes in government or quasi government projects. And in any case that could decide after we have water market in space. Or this might course choose, a few decades from now, assuming we ever get around to exploring the moon.
I tend to think, Moon, Venus, Mars, and Mercury are fine, and we just need to be smart of enough to understand them.
So in sense of not changing the planet Venus, what are it’s advantages in terms early human exploration and settlements. As compared to Mars or Mercury or some other planet.
An advantage of Venus could be it’s nearness to Earth. Lowest delta-v, has more launch windows than Mars, and shorter time of travel than Mars. Though with more delta-v, Mercury as shorter hohmann transfer time than Venus. And again in terms of hohmann transfers, Mercury has shortest hohmann transfer times to anywhere in solar system. Or it’s quicker going from Mercury to Mars than Earth to Mars.
Of course it’s also quicker going from Venus to Mars, then Earth to Mars- assuming one uses hohmann transfer. Though with water market and rocket fuel market in space- one could choose not to use hohmann transfer, and becomes more matter of linear distance between shortest points.
But for freight one will always use the hohmann transfer- and terms broad economics, freight is more important. Though really big freight and time less a problem, there are other ways [ie, Interplanetary Transport Network ]. But it seems that hohmann would remain normal way of freight- as time for freight is also money [Earth’s cargo ships always wanting to go faster].
So one could see Venus as in the middle- fastest to or from Mercury, and fast enough to get to Earth or Mars. Or term of planetary travel Venus is solar system’s goldilocks.
So with Venus one has advantage of a thick atmosphere, and the surface is not really the destination. Obviously if we were sky dwellers on Earth, our bias would be to go
to Venus. But Buckminster Fuller ideas have not been fully incorporated- which probably is very good news- but nevertheless we don’t live in cities floating in the sky.
So Venus is one place one would want sky cities- only other place could be the gas giants- though I guess maybe Titan. So city which would float on Earth, would float on
Venus. And 1 atm on Venus it’s air is only slightly warmer than say, Baghdad in summer.
And could assume one has air conditioning. And having entire floating city at cool and very constant temperature could quite easily managed – and use less energy than any modern city uses for cooling and heating. But of course it’s not particularly cheaper in comparison heat/cooling costs of an Earth floating city. Or a domed city is inherently easier to control the temperature. Or unless wanted a different temperature for whatever your reasons- you would not need a home or office air conditioner. Or jackets or umbrellas. Though one would still want some ventilation- fans or opening a window could be required. So no insulation- but one could want sound damping.
It’s bloody Lefty Utopia- only use mass transportation. Hard to imagine the whole place not being city planned to last detail- there is only one right way for it to be.
So obviously the last place I would want to live. Unless humans changed [and they don’t] it would be like prison or zoo. So the hell would not have much to do with temperature, though they could want it to be sauna temperature- as someone idea population control mechanism, maybe- or part of slogan, Venusian are the hottest people. Though I also see them wanting it below 15 C. As measure to increase demand for winter parkas.
Now, Venus would not have to resemble the novel, 1984.
One could have smaller structures because atmosphere is denser and things float better than compared to Earth’s sky. Plus one has an abundance of carbon- Buckminster Fuller was using concrete and glass, Venus one would use carbon composite and plastic. And not including anything to do with nanotechnology.
Anyhow, the point is early exploration and settlements. Oh, what would you explore for? I normally do this common mistake. I other words, I think NASA should explore the moon in order to find minable water, and NASA should explore Mars to determine how and if humans can settle Mars- largely find cheaper water.
So my premise is NASA should on things which will result in new markets in space,
So what is the market potential regarding Venus?
So can you make rocket fuel? Cheaply.
Of course you have sunlight- if you high enough in atmosphere.
You have hydrogen in form of an acid.
Or why and how is Venus better than Earth?
Moon better than Earth because it has lower gravity- and a vacuum.
Mars is better- because it has more usable land. And more usable solar energy this average land area. Or Moon has trillion dollars worth of water, Mars has at least a trillion dollar of land. And we haven’t explored Mars much- we haven’t explored the moon much- but could say more than Mars. And etc.
So other than shorter travel time, than Mars, what does Venus got?
Hmm. We can get back to denser atmosphere, but Earth is better than Venus in this
regard if include Earth’s oceans.
Or in terms of leaving the planet Earth, it’s ocean appear more useful than Venus thick atmosphere. Or density at bottom of Venus atmosphere is less than 65 kg per cubic meter and water is 1000 kg per cubic meter. And in terms useable Venus has at most 10 kg per cubic meter. Plus Earth has sharp transition from 1000 to about 1.2 cubic meter density- Earth far better in comparison in that regard.
Though Venus atmosphere density could better if make vehicle light enough and/or
big enough. Or Venus has a long and more uniform “run way”.
Or I thought this in post I never made. Put a 200 km wide hole in the ground on Earth
and make it 20 km deep. Yes impossible in many ways, etc, but anyhow.
Now can use the hole [or deeper] which *about* Venus air temperature and air denisty [air temperature increase per lapse rate of 6.5 C per 1000 meter and density
doubles per 10 km. So close enough to Venus.
Now would use that hole to launch into space?
It would be a better place to land from space- slower terminal velocity and parachute
work nice.
Oh that’s interesting, would Venus be cheaper to get to from Space, as compared to Earth [or anywhere else]?
Anyways, this is long, so, so long, but:
Have think more about what does Venus offer in terms of a market for space.
And point is, a market in the near term.
Or what kind of stuff do you look for, if you explore Venus?
Gives a whole new flavor to rockoon launch, doesn’t it?
It seems to me that if the balloon is expandable, it might be better to have a near standard vehicle with a deployable balloot that inflates for reentry. It is difficult for me to see an inflatable tank handling max q during launch. A balloot could be almost any arbitrary size and shape.
If balloon tank construction as in the classic Atlas, I can sort of see the point. Low mass and high volume tank construction would seem to be applicable to both tanks though.
Actually, I’m still trying to wrap my mind around the idea.
–It seems to me that if the balloon is expandable, it might be better to have a near standard vehicle with a deployable balloot that inflates for reentry. It is difficult for me to see an inflatable tank handling max q during launch. A balloot could be almost any arbitrary size and shape.–
With leaving Earth and max q, one could use normal air, start with say 1 psig [15.7 absolute]
And by time of max q atmospheric pressure around 2 to 3 psi, need to have bled off pressure until one has absolute pressure of around 10 psi, and as reaching orbit losing all the air pressure.
And then, when approaching Venus, add the hydrogen gas.
But you got me wondering and was trying to work out how it would work with Venus re-entry- and it seems it needs more than slight modification:)
And I am re-thinking the whole notion that landing a Venus would be/could be significantly easier.
So have go back and look at from angle of how to get from planetary trajectory to merely going a Venus supersonic.
One upshot the re-entry is too hot for aluminum.
Not that I was wed to idea of just using aluminum- I am sort of using it as convenient boilerplate. I was concerned mainly about making things float in Venus.
Or mostly gave up on idea that it could be 5 meter in diameter- and generally 10 meter in diameter or larger is a problem in terms of leaving Earth. As in, such a large diameter not being done at the moment.
Or I assume one has pay payload penalty [at minimum] for large diameter.
Anyways, since I have rashly gone beyond 5.4 meter, maybe I could wildly leap into 15 or 20 meter diameters.
The Vehicle is 96 meters tall
[Oh, this is for Venus floaties, but trying out on Earth, and then wondered if could used
for suborbital, and you know, etc. ]
24 meter diameter base cone with height to 9 meter but sloped at 10 meters.
24 meter diameter .62 meter long ring 3/32″ walls
32 meter diameter sphere
30 meter diameter 60 meters tall cylinder
The 60 meter by 30 diameter cylinder as liner with one closed end and open end.
Open end attached to bottom cylinder with a vacuum holding to top of cylinder.
A liner will be filled to 35 meter below top of 30 diameter cylinder
before launching.
Uses about 2500 kg of gaseous hydrogen.
Will need hot balloon burners for launching from Earth, and these stay on the
ground, and not being attached to vehicle.
On top of 30 diameter cylinder is flat top, structurally designed but equal to
1/8″ [3/32″] thick aluminum 40,000 psi yield.
The 24 meter diameter ring also uses 3/32″ aluminum.
And everything else uses 1/16″ thick 40,000 yield str aluminum.
Where the 32 meter sphere meet the 30 meter diameter top, at point sphere is 30 meter in diameter the sphere past this point is removed, and where 24 meter ring meets it, that section is also removed.
Above 24 meter ring, the cone section seals that end.
The sphere, 24 meter ring and cone section are open to each other and serve a low pressure container- with maximum operating pressure of 5 psig.
At launch, it will start filled with hydrogen gas at or near atmospheric pressure, and as it’s pressurize [psig increases] by lower pressure at higher elevation, the hydrogen will kept below 5 psig allowing the gas into the 30 meter diameter by 60 meter long cylinder [gas held by liner].
30 meter diameter cylinder uses 8.97255 cubic meters of metal: 24225.885 kg
30 meter cap: 3/32″ 1.6832 cubic meter of metal, 4544.65 kg
32 meter sphere: 4.486275 cubic meters of metal, 12112.9425
Piece missing parts from sphere is about 5450 kg of metal resulting
in total mass of sphere to be about 6660 kg
24225.885 + 4544.65 kg + 6660 kg = 35,431 kg
Cone, 24 meter base, 9 meters tall, but angled 10 meters: 2506 kg
24 meter diameter ring .62 meter high, 3/32″ walls: .11125 cubic
meter of metal: 300.40 kg
Total: 35,431 kg + 2506 + 300.40 kg = 38237.4 kg
2500 kg of gaseous hydrogen.
Rocket, payload: 3600 kg
Gross weight: 44,338 kg
Displacement weight at lift off:
Environment is considered to be 15 C, and at sea level
and air density of about 1.2 kg meter cubic meter.
Higher elevation and cooler with as much or denser air
works as well or better. Using above conditions merely because
that what most charts on psi and density and temperature use as
a standard.
Cubic meter volumes:
32 diameter sphere: 17148.6 – 4244.65
12903.95 cubic meter
24 meter ring: 280
24 diameter cone 9 meter, but slope 10 meter: 1504
Total 14678.95 cubic meter
Liner will be filled 35 meter length with hydrogen
With remaining 25 meter of cylinder being hot air. At 30 meter diameter,
area is 706.5 cubic meter per meter length, times 25 is 17662.5 cubic meter
at air density of .9 cubic meters- outside the atmosphere is 1.2 kg.
.3 time 17662.5 = 5298.75 kg
Hydrogen in liner, 35 meter times 706.5 is 24727.5 times 1.2 =
29673 kg
Top container: 14678.95 cubic meter times 1.2 kg = 17614.74
Total: Hot air, hydrogen in liner, and top container: 52586.49
Vehicle has 52586 kg of air displacement weight, and weighs 44,338 kg.
So it could require 8248.49 kg of weight to prevent it from leaving the
ground. But by controlling amount of hydrogen put in the liner, one
hover at near neutral buoyancy not requiring strong cables to keep it down.
Then depend how quickly hydrogen added control it’s lift off.
To decrease density of air, one needs to increase temperature as measured in K,
if double the temperature the density halves. So air at 1.2 kg and 15 C is
273 + 15 = 288 K. Doubled is 576 K. Increased 50% is 432 K [158.85 C].
[“Mylar® polyester film retains good physical properties over a wide temperature range (–70 to 150°C[–94 to 302°F]), and it is also used at temperatures from –250 to 200°C (–418 to 392°F) when the physical requirements are not as demanding.”
http://usa.dupontteijinfilms.com/informationcenter/downloads/Physical_And_Thermal_Properties.pdf
At launch it will not be physically challenging- it’s under no load or stress. And not under stress when in the cylinder. Obviously you don’t heater close to the Mylar- but they are +20 meters above any heater. So air should heat and mix, though hottest air will go the top, and heat the hydrogen- or put in room temperature hydrogen and as air warms the hydrogen will be heated by the air.
Another aspect even if you burnt the Mylar it’s not as dangerous as it could appear to be, because. hydrogen will “mostly” stay at the top of cylinder, and needs oxygen.
It vaguely possible it could put itself out. But probably not good idea to test that theory. Or if had a lot cold air and mixing- and maybe the aluminum would start burning, etc. But with warmer air it is less dense have less of the more abundant nitrogen, but also less oxygen. But if want add water vapor, that also will give you more lift- as it less dense than air. Or I have not attempted to include any added performance of water vapor made by the burners.]
Let’s see how it goes:
Have 8248 kg of lift for 44,338 kg mass vehicle. So it’s going to go up fast, faster than most balloons because no one tries to hold down 8248 kg.
And basically no one wants this much acceleration with balloon.
So if one had 44,338 kg of lift [2 x 44,338 kg in displacement] and could get somewhat close that by immediately filling whole cylinder with hydrogen] then goes at 9.8 m/s/s. But 8248 kg is a fraction of 44,338 kg of lift. It’s .1860. 1.82 m/s/s
And in 10 seconds one going 18.2 m/s and gone up 91 meter, so have not gone very far or very fast. And nothing has really change in regard to the vehicle. You still have lots of hot air in the cylinder and liner is about at same place as it was when you left. One has couple ton of hydrogen and tons of hot air- or 17662 times .9 is 15895 kg, 15.8 tons of hot air. It’s not going to cool down in few tens of seconds. It a very hot sauna you have just turned off the heater- it’s worse, if you expected it to cool down any time soon.
But at the rate that it’s going, soon all of the hot air will be gone.
What happens in 20 second from launch: going 36.4 m/s [81 mph] and have gotten 364.6 meter from the ground.
If you in a hot balloon, and were doing this, you could start to feel the hot rushing out your open bottom of your balloon. Because it’s relatively small hole and you could more hot air than this thing has. So small fraction it could come out, the cooler of hot air first, one would probably not be getting warm, but it would be noticeable.
But from a 30 meter hole, it probably can’t be felt yet- assuming you hang from the bottom of it.
So it’s mildly exciting, but some blimps go as fast as this.
So in 10 second you were going 41 mph, and next 10 second going 81 mph, any car could do this, but not straight up.
Is the air drag at 81 mph for this huge vehicle a lot?
Oh, yeah, got something similar to SpaceShipOne which parked on the cone at the top. And if you up there standing next to it, it would be windy- Cat one hurricane level type of windy. No doubt a force but is significant? And what mean by significant is more than 100 kg of force against the entire vehicle- if was 1000 kg of force I would have add it in in terms reducing the about 8000 kg force. If was 1000 kg, it would
1/8th slower acceleration, reducing by .227 to 1.82 m/s/s.
Because at 364.6 meter elevation nothing has changed much in terms buoyancy or much air leaving or liner going down lower- it’s still somewhere around 8248 kg of force. For instance at 1000 meters rather 364.6 meter:
1000 meter 8.5 C 900 hPa [13 psi] 1.1 kg per cubic meter
http://usatoday30.usatoday.com/weather/wstdatmo.htm
So things are going start changing in next 10 seconds, but is point so far they have not needed any adjustments.
Why not look at next 5 seconds.
25 seconds after leaving the ground: 569.7 meters above the ground and 45.5 m/s [101 mph].
As a guess, less than 1 ton of hot air has left from bottom of cylinder, and if someone is hanging down at bottom of cylinder they probably would feel a breeze of warm/hot air. Of course, if stuck head beyond the cylinder wall, there is 100 mph wind flying past.
If one is up at the cone area with the SpaceShipOne, one could be getting rather hysterical.
I parked the SpaceShipOne type craft on the cone and it’s somewhat at near a 45 degree angle- maybe it’s 35 to 40 degrees. Naturally it would seem prudent to be tied to something if one were up there.
I am wondering about forces upon the vehicle which resembles SpaceShipOne. In seems at 100 mph is near it’s takeoff speed if it wasn’t full of rocket fuel.
But the speed of the wind speed isn’t coming at it, in a very horizontal fashion, though one could argue that the cone is deflecting the wind so it’s horizontal.
So if you could look at the person tied on, would he pressed down on the conic surface or mostly being blown off the cone?
Now being more than 1/2 way to 1000 meters, we could roughly 1/2 the values given above and see what kinds effects they would be having on how fast this is now accelerating, and also ask if the +100 mph is now having a significant
amount drag.
1000 meter has reduction in air temperature going from 15 C to 8.5 [6.5 C, which is the normal lapse rate on Earth- it can be a bit lower reduction in temperature if it’s highly humid- or not like Venus].
Since this change has nothing to do with heat loss, and what is called the adiabatic [un heat] lapse rate, the hot air inside the cylinder is also at lower pressure [and density]. So if 150 C at ground, than it’s about 3 1/4 C lower in temperature at halfway to 1000 meters.
The pressure difference is 14.7 to 13 psi. Halfway, it’s a .85 psi change. That means the 32 meter sphere and the cone which were at 14.7 are still at 14.7 of pressure due hydrogen but are now at .85 psig.
The hot air which was at 14.7 is now at 13.85 psi [absolute] and it density has lowered by 1/2 of .1 kg, or they started at .9 and are now .8.
At .9 the mass was 15895 kg. If one doesn’t count liner moving downward, .8 times 17662.5 is 14130 kg. 15895 – 14130 is 1765 kg.
That’s a bit less than 2 tonnes, and I would guess 1/2 or more left the bottom end of the cylinder in last 5 seconds. Would guess each second like 100 kg, then 150, then 200, 300, and 500. Totals 1250 kg.
I would guess that exponential rate does not continue, just due to the lower pressure- and it’s also got something like exponential decrease from it running out of mass. But it won’t be allowed the same volume, as liner will push/replace it’s volume.
And what hydrogen doing in the liner? It also must expand, and it was at 14.7 psi [absolute] at sea level and now, must be at 13.85 psi. So if pressure 1/2 of 14.7 psi, then it would occupy twice it’s volume.
So it starts at 35 meter and so would expand to 70 meter [cylinder is 60 meters] so the liner would stick out the back by 10 meters.
Which helps illustrate why no hot air can not remain in the cylinder. So that happens when pressure is 7.35 psi.
But it’s at 13.85 psi.
Halfway between 14.7 and 7.35 psi is 11.025 psi. So instead 35 meter it will go 17.5
meters at 11.025 psi. And halfway between 14.7 and 11.025 psi is 12.8625 psi and the distance of 8.75 meter.
And halfway between 14.7 and 12.8625 psi is 13.781 psi and a distance of 4.375 meters.
So it’s about 13.85 psi and at 13.781 the liner will have move down 4.375 meter.
And that will happen in some fraction of second from this point of 25 seconds from launching. Or can assume liner has moved 4.375 meter by 25 seconds from
leaving the ground. So that means 706.5 times 4.375 meter or 3090.9 cubic meters is no longer available for the hot air to occupy. Or additional 2472.75 kg of hot air has left the building.
Was allowing 14130 kg so – 2472.75 kg which is 11657.25 of hot air to remains in the cylinder.
There are probably many theoretical questions, one could ask regarding the rapid departure of such quantity of hot air within a relatively short period of time.
I wonder if the hot air is heating the hydrogen and if so by how much.
What does not seem like theoretical question is that the guy hanging under cylinder would feel the hot air- despite the large size of it’s diameter.
Since got how much, air remains we can look at amount lift is available at 25 seconds point after leaving.
Hot air was causing 5298.75 kg of 11657.25 is remain and assume about same .3 kg = 3497.175 kg
A loss of 1801.575 kg of lift
whereas increase volume of liner going from 35 to 39.375 cubic meter.
For liner and for container volume the 1.2 kg has reduced to 1.15 kg per cubic meter. 39.375 is 27818.4375 cubic meters which is 31991.203 kg. Was 29673 kg
An increase of 2318.203 kg
The container: 14678.95 times 1.15 is 16880.7925
With loss of 733.9475.
If add losses together: 2535.5225
giving 2535.5225 – 2318.203 which is net loss of 217.3195
Or 8248 kg is reduced to 8030.6805 making acceleration 1.775
Which more significant than I thought would be considering low it still is.
1.82 minus 1.775 is .045 m/s/s
But at 100 mph, imagine air drag would as much or even more, doesn’t seem likely it’s more than .2 m/s/s.
And it seems the air coming out the back cylinder would be significant factor in reducing overall air drag.
If just use a constant acceleration value of 1.8 m/s/s in 30 seconds
from launch we get distance of 810 meters elevation and 54 m/s [120 mph]
Or constant of 1.7 m/s/s in 40 seconds distance of 1360 meter and 68 m/s [150 mph]
One can use higher portion of hot air to amount hydrogen- for numbers of reasons.
One reason is if wanted to avoid air drag at lower elevation, so you wanted a slower acceleration like 1 m/s/s and for 45 seconds. 1012.5 elevation and velocity of 45 m/s [100 mph].
And by my calculations 4600 of lift will start with 1.01 m/s
To get to 1000 meter and be going same velocity as with 1.82 m/s/s did in 25 seconds. And 8248 – 4600 is 3648 less lift- by using more air and less hydrogen.
So copying from above:
— Liner will be filled 35 meter with hydrogen
With remaining 25 meter of cylinder being hot air. At 30 meter diameter,
area is 706.5 cubic meter per meter length, times 25 is 17662.5 cubic meter
at air density of .9 cubic meters- outside the atmosphere is 1.2 kg.
.3 time 17662.5 = 5298.75 kg
Hydrogen in liner, 35 meter times 706.5 is 24727.5 times 1.2 = 29673 kg —
Try 30 and 30:
hydrogen: 25434 kg Air: 6358.5 = 31792.5
Was: 29673 kg + 5298.75 kg = 34971.75
34971.75 – 31792.5 is 3179.25
Try 28 H2 and 32 air: H2: 23738.4 Air: 6782.4 = 30520.8
34971.75 – 30520.8 is 4450.8
Whatever, go with it
8248 – 4450.8 is 3797.2
3797.2 divide by Gross weight, 44,338 kg and it is .8392 m/s/s
Do 50 seconds:
1049 meter elevation and 41.96 m/s [93 mph]. Bring chart down:
1000 meter 8.5 C 900 hPa [13 psi] 1.1 kg per cubic meter
So where is liner at? Started at 28 meters and at 14.7 psi. Lost 1.7 psi
And above, said: “And halfway between 14.7 and 11.025 psi is 12.8625 psi and distance of 8.75 meter.”
And 1000 meters it is less than 12.8625 psi
So was halved and halved: 28, 14, and 7
28 plus 7 is 35 meter.
So liner at same level as I started with from last time. So it’s going to accelerate
faster? hmm. Density is only less by .1 kg.
Well a part of plan was to not have calculate so often, but if increasing acceleration at this level then it would started to acceleration with increasing rate, oh, maybe as much as 20 second ago.
Anyways I think I might have found a new rule: use as much air as possible as long as getting any acceleration.
Better check it.
Oh btw, it’s almost the exact opposite of a rule with rockets.
I never going to get this rocket launched.
So:
35 times 706.6 times 1.1 kg is: 24727.5 kg
25 times 706.5 times .3 is 5298.75 kg
container: 14678.95 cubic meter times 1.1 is 16146.845
16146.845 + 5298.75 + 24727.5 kg is: 46173 kg
Gross weight: 44,338 kg
difference of 1835 kg
Now I am very confused.
Oh, it supposed to be 27200.25- 24727.5 was how many cubic meters it was.
+2472.75
total: 4307.75 kg of displacement
So it is increasing the rate of acceleration- not by much.
Checked everything twice. Ok.
Now, going .9521 m/s/s, at 41.96 [93 mph] at 1049 meters elevation. At 13 psi with containers at 1.7 psig. We miraculously all sudden got bump in acceleration now, instead of 10 seconds ago.
Maybe will we left the emergency brake on or was dragging a dead cat.
Never-mind, launch later.
It goes on and on, and maybe someone can patiently explain how it’s all wrong,
or impossible to make.
I had some fantastically improbably ways of making them on the Moon.
Ok, molds made from dust and molten sprayed aluminum, that’s all I am going to say.
Gbaikie…
Your comment is longer than my original blog post! You need to get your own blog, and then just post a link in the comments maybe with a 1-2 line summary of your conclusions. Sheesh. 🙂
~Jon
I sorry about the length of the post.
But I think I addressed this bit:
“You’d most likely have to attach payloads to the side not the top of the balloon because you probably want the balloon at as low a pressure as possible when it reaches orbit.”
I think one can get to higher elevation and launch at some velocity by having rocket on the top of the balloon. Though I think it has to be quite large, in particularly a large diameter. Though it low pressure in terms of about 5 psi, and starts out at 0 psig.
**Start small/bootstrap. **
**And is possible Venus could be commercially used before the Moon?**
Main advantage of Moon is you can sell rocket fuel to High earth orbit.
What advantages of Venus
Is easier to live on Venus?
Is easier to live in 1 atm at 1.5 air density
The sun moves slowly- our sun travels at about 1000 mph across the sky,
on Venus it’s about 4 mph.
Venus has trillion of tonnes of hydrogen in it’s sulfuric clouds
Venus shiny stuff on higher elevation mountains, which is lower in elevation
that the sulfuric acid clouds can reach.
Therefore combining the shiny stuff on mountains with hydrogen sulfuric cloud could
have some kind useful chemical reaction, or seems possible to me that heat and electrical energy separated them in first place- or that it could even be sort of like a kind of “fossil fuel”.
Whatever is on the mountains should explored, and if going to go anywhere on Venus surface, it seems the place to go is at highest elevation of the surface.
But going to the surface is sort of mining the ocean on Earth- we do a lot oil
mining on ocean, but it’s generally costly.
And mining highest mountains would be like mining the shallower seas.
It’s also possible one would want anchor ships of Venus, and highest mountains
could be useful location in that respect.
One could say the main problem with Venus is the lack of exploration, the Moon
also lacks exploration, but has enough exploration [in a delayed and haphazard fashion] to cause some suspicion that the lunar poles could have minable water.
So in terms of the matter of whether Venus could be used prior the Moon [or sometime soon], could be directly related to whether Venus is explored.
Now, one could ask, is it cheaper to explore Venus as compared to other destinations?
Perhaps a more specific or harder question is- is it cheaper to do a sample
return from Venus?
Or Mars sample return has been something desired for decades, but it’s
deemed too expensive and therefore this sole factor has been prevented it for occurring.
Could you get sample return cheaper from Venus as compared to from Mars?
Or it’s more expensive or about the same cost, it seems Mars would be easily selected before a Venus sample return.
Let’s start with, you land a helicopter on mountains, get sample return, take off meet
up with Venusian floatie, and the floatie somehow used get small payload off
Venus and back to Earth.
“NASA thinks it might have a solution that will allow sending humans up to check it out, though: Cloud City.
The High Altitude Venus Operational Concept — HAVOC — is a conceptual spacecraft designed by a team at the Systems Analysis and Concepts Directorate at NASA Langley Research Center for the purposes of Venusian exploration. This lighter-than-air rocket would be designed to sit above the acidic clouds for a period of around 30 days, allowing a team of astronauts to collect data about the planet’s atmosphere.”
http://www.cnet.com/news/nasa-wants-to-build-a-floating-city-above-the-clouds-of-venus/
Linked from:
http://www.drudgereport.com/
“It’s also important to note that Venus is often significantly closer to Earth than Mars is. Because of how the orbits of Venus and Earth align over time, a crewed mission to Venus would take a total of 440 days using existing or very near-term propulsion technology: 110 days out, a 30-day stay, and then 300 days back—with the option to abort and begin the trip back to Earth immediately after arrival. That sounds like a long time to spend in space, and it absolutely is. But getting to Mars and back using the same propulsive technology would involve more than 500 days in space at a minimum.”
http://spectrum.ieee.org/aerospace/space-flight/nasa-study-proposes-airships-cloud-cities-for-venus-exploration
And:
“Venus has value as a destination in and of itself for exploration and colonization,†says Jones. “But it’s also complementary to current Mars plans.…There are things that you would need to do for a Mars mission, but we see a little easier path through Venus.†For example, in order to get to Mars, or anywhere else outside of the Earth-moon system, we’ll need experience with long-duration habitats, aerobraking and aerocapture, and carbon dioxide processing, among many other things. Arney continues: “If you did Venus first, you could get a leg up on advancing those technologies and those capabilities ahead of doing a human-scale Mars mission. It’s a chance to do a practice run, if you will, of going to Mars.—
I would also say that rather than just practice, Venus could provide way to get to Mars quicker.
The problem with Venus is it takes a lot of delta-v to leave it’s deeper gravity well.
But there is shortage of acid to make into rocket fuel.
So once get to point of having capacity of sending crew to Venus atmosphere and getting the back to orbit [by making rocket fuel] the part of merely making more rocket fuel or continuing using the infrastructure and technology would the easy part.
It seem crewed Venus is plausible but would need about as much robot exploration of Venus as we had to Mars before one getting enough information prior doing Manned mission.
But anyhow it’s nice they considering it as an possible future option.
Query: would there be any problems in using such a balloon as the tether for a space elevator?
A space elevator anchored to a buoyant platform is indeed a possibility, presuming a sufficient strength material. How short a “day” could we get by selecting an altitude for favorable winds around Venus?
About 4 Earth days on average, but can be as low as 3 Earth days, particularly in the polar ‘collars’ (which have other advantages, such as being cooler, denser, and in the North, travelling above the continent of Ishtar Terra).
The actual poles are covered by insane vortexes, while the winds at the equator are slower than normal.