Mission to Venus

Void · 2014-12-19 06:52:20

Actually I am surprised that nobody picked up on this.
http://phys.org/news/2014-12-nasa-possi … venus.html

Actually interesting. Might support the passage to Mars and Mars settlement in the long run I think.

RobS · 2014-12-19 08:07:28

The idea of big solar powered blimps is not new. The problem I see with this article is that it would be immensely difficult to get people from the Venus atmosphere back to orbit. The energy required is only a little less than to launch from the surface of the Earth to LEO. So, you want to put a Falcon 9 on the blimp? How will you refuel it? The blimp's mass would have to change by hundreds of tonnes, too, as the Falcon refueled (hydrogen is damn hard to extract from the Venus atmosphere) and then when you release the Falcon, its mass would instantly decrease by hundreds of tonnes. It would be easier to haul those hundreds of tonnes to low Venus orbit to provide shielding for an orbital station, which would be in a radiation environment not that different from ISS anyway. The astronauts would be 200 km up instead of 50 km, which wouldn't make that much difference to the science.

Void · 2014-12-19 09:07:32

I'm really not qualified, but I started this so, an attempt must be made.

Could a retrieval device drop down by gliding, and under power, drop a basket and hover. The persons would have to get into the basket (In suits), and somehow survive a move to orbit. That is after in the basket, quickly get into an un-pressurized cab?

Granted that's sci-fi, but Venus does have an about 90% gravity field? So slightly favored by that.

I just posted the article however, I thought it would be of interest to those who want to colonize Venus, and also a break from the current carnage going on in other locations of this site.

In addition to the gravity favor, there are additionally favors of;
-Temperatures
-Pressures
-Radiation Protection

So, some of the rigors are relaxed relative to Mars or the Moon.

So, maybe a glide, hover, space shuttle while a burden is balanced out by the favors, and the mission is not quite so impossible.

And then as stated in the article, the solar energy situation is much more favorable, both for the interplanetary flight, and for life support when in the envelope of the atmosphere.

But if you want the truth, I would favor expendable robots working with an airship, and if sample return was desired, I think that could be arranged. Obtaining propellant from the atmosphere might be possible.

I would certainly think that should be done first.

And then if you have all your scientific information, there is no reason to expose humans to risk unless you plan to build floating cities.

Last edited by Void (2014-12-19 09:17:00)

Decimator · 2014-12-19 10:27:34

Any reason (other than "Oh my Budda, nukes!") that we couldn't make a CO2 NTR? Something that combines aspects of Project Pluto and NERVA.

SpaceNut · 2014-12-21 17:02:05

A quick little advance google of NewMars indicates that we have had a strong love of Balloons for all types of useages and this is just another case of what we can make use of in this new topic to help fledge out a how to make it possible...

Vacuum baloons

Airship to Orbit?

Balloons to Space

Floating Venusian cities or Venus vs Mars vs Titan revisited

Given the recent rennaissance in Venutian Cloud Cities here

Dirigibles on Mars - A practical means of transport?

RobertDyck · 2014-12-21 19:36:50

Decimator wrote:

Any reason (other than "Oh my Budda, nukes!") that we couldn't make a CO2 NTR? Something that combines aspects of Project Pluto and NERVA.

A nuclear thermal rocket works by heating propellant. Specific impulse is calculated by gas expansion, and molecular weight. Using CO2 wouldn't have the same specific impulse as liquid hydrogen, but would work.

We have discussed this before. My great wonderful idea, was a bit more gradiose than balloons. Build a shuttle specific for Venus. It would use Project Pluto nuclear jet engine for take-off and acceleration to the upper stratosphere. Or Venus equivalent. The NTR for the final push to Venus orbit. Design it for Venus pressure, and Venus corrosive atmosphere.

Remember heat shields for the Shuttle used highly pure silica, so would be as resistant to sulphuric acid as glass. Thermal blanket, known as AFRSI, were a quilt: outside fabric was the same highly pure silica woven as cloth, inner fabric was normal fibreglass, batting was fibres of the same highly pure silica. Black tiles had a glaze to radiate heat. Blankets had a water proof coating in case of rain before launch. No rain on Venus. And use ALON for the windshield instead of glass, because it's much stronger, resistant to micrometeoroids. ALON is aluminum oxide with a touch of aluminum nitride, as a ceramic. Sapphire is aluminum oxide as crystal. ALON is as resistant to acid as sapphire: completely innert to sulphuric acid. Venus has that acid in clouds, but carbonyl sulphide near the surface. Glass, silica, and ALON are all immune to that as well. ALON melts at 2150°C, Venus surface is about 450°C. So ALON can take the heat. Heat shields are not sealed against the skin, they're designed for high speed air flow, so corrosive can reach the metal skin. Coat in a "glaze", a coating of glass as thin as a coat of paint. To ensure it has some flexabilty for thermal expansion, use gorilla glass. It's alkali-aluminosilicate; basically a glass, so also acid resistant. The Venus shuttle would require a Project Pluto style nuclear jet engine, because it has to land then take off as a SSTO. And Venus has 90% gravity.

What do you think? Landing rockets, or vectored thrust like a VTOL fighter jet?

It would need a nuclear reactor to generate power, with ability to radiate waste heat into +450°C Venus ambient. It would need that power to run refrigeration. Gotta keep the cabin cool enough for humans. With a nuclear jet engine, you may be able to carry rocket propellant from Earth. But you could use liquid CO2, harvested from Venus atmosphere. More refrigeration. And liquid CO2 has much greater density than liquid hydrogen, so much smaller propellant tank. For a land/take-off SSTO with heat shield, tank size is important.

Power generation is dependent on temperature difference between reactor core and heat sink. SP-100 was designed for a maximum core temperature of 1377°C, SAFE-400 for max 1020°C. (Source: Encyclopedia of Earth). They would generate less power on Venus than Mars or space, but would still generate power. SAFE-400 is the newest and lightest, but would generate about half power on Venus.

If you want to do something like this for Earth, you would use steam distilled water for propellant.

Venus Spacesuit: based on the Newtsuit or Exosuit. Both made by the same company. Commercial versions maintain 1 atmosphere (ocean surface pressure) inside the suit, and are rated to dive 1000 feet. The US Navy contracted this company to upgrade it with military ceramics, the result is rated to 2000 feet. And the website says for enough money it can be upgraded for even greater depth. That would be done by replacing aluminum alloy with titanium alloy. Venus surface is equivalent to 3000 feet. I'm thinking ALON visor instead of acrylic; for strength, heat resistance, and corrosive resistance. This wouldn't have the water thrusters, but it's heavy and Venus has 90% gravity. So this would require power assist. Exoskeletons have already been developed. And the suit would require refrigeration; probably by a tank of liquid nitrogen. EVA would be limited by coolant.

Last edited by RobertDyck (2014-12-21 23:55:14)

Impaler · 2014-12-21 19:42:01

I don't think Hydrogen extraction from the Venus atmosphere is that hard for an established settlement, the cloud city would be floating at an altitude that has Earth sea-level pressure and that means the outside air is dense enough for processing at reasonable cost (costs scale with fan size which scale with volume of air processed). And then you might considered the possibility of putting the air-processing equipment at a lower elevation on a cable/s suspended from the city to put it at an even denser and perhaps more attractive atmospheric layer.

To make the sudden mass change of a rocket launch less jarring I would lower a cable to the surface, on the end of the cable are two large weights separated by a short segment of cable, just a single meters long, these weights would stack on-top of each other like plates, one on the ground and a second one on top of it. The balloon city buoyancy is adjusted so both weights are sitting on the ground with minimal tension on the cable, then when the rocket is released the second weight which is equal to the rockets weight will be lifted off the ground immediately replacing to rockets weight, the first weight will remain in contact with the ground and keep the city stationary during the rocket assent and then later the city can increase buoyancy (probably by releasing ballast of compressed atmospheric gas) and lift both weights off the ground to do the whole thing again some day.

As the cloud city will be able to expand almost exclusively on atmospheric mining they may simply end up with a good amount of water as a byproduct. And they do have abundant solar energy to do everything with so processing lots of air volume and cracking water and storing the hydrogen should be do able. I don't think most people realize how practical moisture extraction from the atmosphere can be, it is likely to be better then mining ice on Mars and virtually every planetary atmosphere has some water vapor in it.

Also the NASA animation shows a very conventional entry with heat-shields etc, I wonder if it is possible to just inflate a balloon in orbit and then slowly and gently come out of orbit with that. Because your already buoyant once you go below a certain altitude your no-longer falling and your entry can stretch out in time almost infinitely at high altitude. You would initially be moving with excessive horizontal velocity but if you use a lifting body shape you transfer that to upward velocity and ride higher into the atmosphere, maybe bouncing multiple times and keeping the heating to controllable levels. Thus it may be possible to build/assemble the whole cloud city in Venus orbit and then lower it into the atmosphere when

Last edited by Impaler (2014-12-21 22:52:09)

Impaler · 2014-12-21 20:05:44

I don't' think NTR works on Venus, bringing liquid hydrogen to the surface of Venus and keeping it liquid while you do the surface exploration would be a nightmare. CO2 has a such a high molecular weight that it gives terrible ISP compared to hydrogen but if your breathing it in from the atmosphere it is free fuel and the ISP looks better, unfortunately CO2 is neither a fuel or an oxidizer so the T in NTR is all that your getting, hotter exhaust of the same gas you ingested with no chemical release of heat or molecule count increase. An air-breathing engine alone can't reach orbit so you would have to switch to rocket thrust at some point and do MOST of the Delta V on that, but NTR has never been shown to have the Thrust-2-weight necessary to hover let alone ascend on Earth so it looks like a dead end for Venus.

I'd just go with a CO/O2 rocket slung under a blimp with the rocket fueled by cracking atmospheric CO2, as rocket gets heavier additional balloons are inflated with waste byproducts lighter then CO2 from the atmospheric processing, N2 and O2 both work. The ISP of the CO/O2 rocket will not be great and 3 stages to orbit might be necessary.

I think doing all our visits to the Venus surface from a 'cloud base' would be more practical then sending a landed vehicle to the surface. The floating cloud-base would just drop and anchor and come to rest relative to the surface, then a cable-crawler cage carrying out astronauts would descend to the surface. The cable would have embedded power and communication lines which would send the abundant solar power being collected at the cloud-base down to the surface team which would could be used for cooling, life-support replenishment, operation of heavy machinery and recharging of any ground vehicles. Weather instruments and radar could also be placed in/on the decent cage and it could be continually left dangling under the base to collect data at any desired altitude.

The cloud-base can reposition itself by simply floating with the prevailing winds and reach virtually any place on the surface. It will also allow most of the cloud-base to be manufactured to lower thermal/pressure requirements with only the 'drop cage' and surface stuff made super durable. The sulfuric acid issue may also be reduced at high altitude though I am not sure if it acid-proofing can be avoided entirely the lower density and temperature should mean that any acid encountered is that much less aggressive. Finally the return to orbit is more attractive from a cloud-base because of reduced air-drag, though it is generally a minor part of our overall rocket launch problem here on Earth the drag would be absolutely killer on Venus and may make launch absolutely impossible. From a cloud base we can be very confident that any rocket capable of reaching orbit from Earth will work, so you could just slap that Falcon-9 under the belly of the blimp like in that NASA video.

Operations would be just like deep-sea diving, so use of hard-shell suits looks very attractive, I agree that powered exoskeleton will have to be added but this is not insurmountable as it's just the combination of two existing technologies. I'd give the suits power-cable umbilical of about 100 yards that automatically real in and out so most operations can be done right at the site of the anchor cable without running down batteries, it is unlikely that sufficient power for an 8 hour EVA can fit in the suit without making them nearly the size of vehicles, so just a short 15-30 minute battery would be used for emergency. Alternatively maybe we DO just want to put people in a rover vehicle, way simpler, but then that would not count as 'setting foot on' so no foot-prints, and no glory, and who wants a flag planted by a robotic arm?

Kind of trippy to think Man might set foot on Venus BEFORE Mars.

Last edited by Impaler (2014-12-22 03:15:09)

RobertDyck · 2014-12-21 23:54:08

Impaler wrote:

CO2 is neither a fuel or an oxidizer so the T in NTR is all that your getting, hotter exhaust of the same gas you ingested with no chemical release of heat or molecule count increase.

Decimator mentioned "Project Pluto". That's the hole basis of Project Pluto. We've discussed this before, but that was before you joined the forum. Welcome newbie.

An air-breathing engine alone can't reach orbit so you would have to switch to rocket thrust at some point and do MOST of the Delta V on that

We've had this discussion many, many times. The Space Shuttle re-entered the Earth's atmosphere at mach 25. That implies it could leave the atmosphere at that same speed, and only require an OMS burn for circularization. The hypersonic air breathing boys talked about a SCRAM jet achieving mach 17. Then X-43A demonstrated mach 9.8 (not quite mach 10). Then ATK Thiokol got the NASA contract to explore hypersonic speed up to mach 20. Good for them, I hope they achieve it. That would mean achieving most of the speed needed for orbit, with just a small push by a rocket.

NTR has never been shown to have the Thrust-2-weight necessary to hover let alone ascend on Earth so it looks like a dead end for Venus.

NERVA development ended in 1974. Thrust (sea level) 399.500 kN/40,741 kgf, engine mass 11,860 kg, Isp in vacuum 825 s, Isp at sea level 380 s.
NERVA 2 design study 1991. Thrust 333.00 kN, engine mass 8,500 kg, Isp in vacuum 925 s.
Timberwind 45 development ended 1992. Thrust (sea level) 441.30 kN/40,050 kgf, engine mass 1,500 kg, Isp in vacuum 1,000 s, Isp at sea level 890 s.

Note: Timberwind 45 thrust to engine weight ratio = 26.7
This is why I've been gushing about Timberwind for so many years. It took a long time before I found how they achieved such a low engine mass. Timberwind used Americium-242m while NERVA uses highly enriched uranium (>99% U-235). Americium allows a smaller critical mass. Energy density is not higher, but you don't need to carry nuclear fuel for multiple years at full thrust. A launch to orbit lasts what? 20 minutes?

Timberwind was developed as part of SDI, also known as Star Wars. It was intended for a ground launch ICBM. This obviously raised the question "Why a nuclear ICBM?" But the point is Timberwind was designed for ground launch; so it can do the job.

This is also why one manufacturer of military drones has started development of a nuclear jet engine using Am-242m. The advertised objective is a drone that can stay aloft for months without landing. So that means nuclear thermal jet engine development has begun.

Kind of trippy to think Man might set foot on Venus BEFORE Mars.

Venus is technically possible. And I gave the technologies necessary. But it's still significantly harder than Mars. The only way that would happen first is some political or bureaucratic crap.

Last edited by RobertDyck (2014-12-23 12:30:24)

Impaler · 2014-12-22 03:04:04

A meteorite can enter the atmosphere at Mach 25 too, that doesn't mean it can propel itself to that speed, the two have nothing to do with each other.

Our ramjet technology use hydrocarbon fuels and atmospheric oxygen so they have released chemical energy to work with and the heat is IN the working gasses rather then having to be transferred through the solid engine, they are at the edge of their performance to just barely reach thouse double digit Mach number because they fundamentally have to plow through air (even if it is high altitude air) and suffer huge drag losses. If you try to go to higher and thinner the engine needs to physically get bigger to scoop the needed air to produce the needed thrust and it becomes excessively larger which eats up the mass fraction for the rocket system that will in the end produce the final thrust.

Thus in any kind of practical orbital assent you leave the bulk of the atmosphere ASAP around mach 5 and no air-breathing system can meaningfully contribute beyond that point. The only marginally viable solution the Skylon gets around it by near liquifying all of it's intake air and feeding it into a rocket so they are a rocket ALL the way but switch oxidizer source from external to internal.

The NTR's hydrogen propellent systems in which your running a cryogenic or at least not yet hot fluid through the engine to pick up huge amounts of heat.

If you try to combine thouse things they don't work anymore, the incoming 'air' in a ramjet/SCRAM jet is being compressed and is thus already hot, transferring heat to an already hot gas is not as efficient and if the gas has already reached the temperature level of the best heat resistant materials the core is made of, then no heat-transfer is possible. Without heat-transfer you their is no thrust because their was no chemical reaction in the engine (also without heat-transfer the nuclear fuel just melts-down). Trying to breath Venus atmosphere gives much poorer ISP so in this specific role of assent from a floating Venus city their is hardly any advantage over the CO/O2 rocket.

The Pluto concepts were for engines operating at only Mach 3-6 going above that it breaks the thermodynamics. And while the Thrust-Weight of the best NTR might be near 30 that is quite low by rocket standards and will still present considerable increase in dead-weight over chemical systems, air-breathing systems ALWAYS have lower thrust-2-weight of rockets (often an order of magnitude) so again it is questionable if such an engine could get off the ground, we are already unable to get a SCRAM jet to leave the ground and have to accelerate them with rockets up to several mach, this is all due to the thermodynamics of moving through air at progressively higher speeds, it completely changes how the engine has to operate and we can't make an air-breathing engine that can function through all thouse regimes from stationary to mach 25. Adding nuclear heat doesn't solve any of thouse problems, and if anything probably makes them worse as I now have something in my engine that demands huge cooling.

It seems that no matter how inappropriate someone on this forum will always try to throw NTR at a mission, the obsession with this dead technology is just staggering to me.

Last edited by Impaler (2014-12-22 03:10:51)

RobertDyck · 2014-12-22 09:20:07

Are you being a troll? Or do you really not understand how to develop anything new? The stuff I'm talking about is not radical, it's an incremental improvement on existing technology. Fairly simple. One of the problems with NASA is it lost its "can do" attitude. They were able to achieve amazing things, achievements radically new. The reason they were able to do so was the belief that they could. And a lot of hard work. But you aren't going to even start the hard work if you keep arguing that it can't be done. NACA was created specifically to research high-risk/high-payoff technologies for aircraft. The aircraft industry was too timid to work on that. It worked, aircraft developed a lot more quickly because of NACA. After Sputnik, NASA was transformed into NASA. Before Sputnik, the US didn't even have an ICBM. They puttered at missile technology, developed intermediate range missiles. But competition from Russia forced them to get off their ass. The US converted NACA into NASA. And they did achieve great things. Today, NASA engineers couldn't design Skylab. They have developed Mars rovers. But the human spacecraft guys are infected by people like you. Those who can't see beyond the end of their own nose.

No, nuclear thermal jet engines are not restricted to liquid hydrogen. That propellant has the advantage of high Isp, but the problem of storing an extremely cold cryogenic propellant, and extremely low density requiring extremely large tank.

Impaler, you have consistently argued that it can't be done because it hasn't already been done. You keep saying this, over and over again. The Mars Society is all about achieving something that has never been done before. Your attitude is incompatible with this organization. Please leave.

Terraformer · 2014-12-22 09:45:13

Robert, have you not read the posts by GW about Scramjets? There is a big difference between reaching high velocity within the atmosphere and staying at high velocity there. You deal with incredible amounts of drag, and that means heating. Which you can take for a short while, but not long enough to reach orbital velocity, even if you have a nuclear reactor that could theoretically get you there.

GW Johnson · 2014-12-22 13:02:15

Biggest problem with airbreathers RE: going to orbit is really twofold. (1) you have frontal thrust density in the thick air, but the heating (external and internal) gets exponentially more unsurvivable as you speed up. (2) in the thin air, heating (at least externally) is more survivable, but you haven't got any frontal thrust density because you really hardly have any air to breathe. A third problem is that above design speed, thrust actually decreases some, while drag increases exponentially.

The fundamental problem is climb rate in the thin air. hdot = (T - D)/W. In the really thin air above 100,000 ft or 30-ish km, D is low because density is low, but so also is thrust. T-D might still be a positive number, but it gets really small compared to W. W has nothing to do with thinning air density. Its only reduction is fuel burnoff. Service ceiling for an aircraft is usually defined as inability to climb at more than a minimal rate, usually in the vicinity of 200 feet/minute.

Once your rate of climb capability declines to near zero, you won't even accelerate any further, much less climb. That's just (T - D)/W going to zero. Not dealing with that at the outset is one of the two fundamental reasons X-30 died: (1) scramjet is an airbreather; at 150,000+ (T-D)/W has gone to zero, or even negative, and (2) at that time scramjet was an unready-to-apply technology. It still is. They couldn't shed the notion of this thing climbing and accelerating on scramjet alone, going through 200,000 feet. Ain't ever gonna happen.

What you do, if you want to use a fast airbreather airplane to help get you to orbit, is figure out how fast it can get you moving (the T = D maximum speed point) but down at an altitude where you actually had the climb rate (T-D)/W to get you there fairly quickly, flying at a speed where the T-D margin is highest. That's usually well under 100,000 feet, climbing around Mach 2.5 to 3, even if your plain ramjet peaks out at Mach 5 or 6 in level flight way up there.

Plain ramjet takes over just under Mach 2 if you design it right. What that means is you get pretty good ramjet Isp (well above 1000 seconds) during your climb, and during the first part of your pullover and acceleration at altitude. Isp will inevitably decrease as you accelerate beyond Mach 3 to 4. By the time it reaches T=D at near Mach 6, the Isp will be a bit under 500 seconds, maybe slightly under 400 seconds. Depends on how good a job you did designing and selecting the right inlet components. That's an art few know.

So, you need rocket to get you from Mach 0 to just under 2, you fly ramjet from there to Mach 6-ish at altitude, and then you have to go back on rocket from Mach 6 all the way to 8 km/s orbit speed. That last is best done by pulling up to about 40 degrees and climbing out of the air quickly, then gravity-turning to orbit altitude as you accelerate. That's simply what you have to do. Airbreather delta-Mach is just over 4 with ramjet. That's more than a turbine=powered airplane can provide, even starting from rest, because of engine overheat problems that begin about Mach 3.2 to 3.4-ish with turbine.

If scramjet were ready to apply (and it is still not), the min takeover speed is Mach 4. I don't see a thermally-survivable design that could go much faster than about Mach 10, more likely Mach 8, with kerosene-type fuel. 10 and up would require hydrogen, and these things are very harshly volume limited. You really DO NOT WANT a hydrogen scramjet because of that volume-limited aspect to spaceplane design. Say we can get Mach 8, that's a delta-Mach in airbreather of about Mach 4. If 10 is actually feasible on kerosene, then the delta-Mach in airbreather is more attractive at 6. If not, then why bother with scramjet? Ramjet is so much simpler and more ready-to-fly.

It wouldn't be much different on Venus, except your systems would have to be nuclear, and that's even less technologically-ready than scramjet. By far.

Project Pluto was a boost-to-cruise nuclear-thermal Mach 3 ramjet design. It was a low-altitude cruise design, under 1000 feet, actually. They did some direct-connect-type ground tests with it at the Nevada nuclear test site (not far from Jackass Flats where NERVA was tested). The nuclear ramjet would have killed more people on the ground flying to its target (very badly radioactive exhaust, plus lethal sound levels from its shock wave) than with its megaton-range warhead at the target. That was the state of that art circa 1963. Not much has been done since then.

GW

JoshNH4H · 2014-12-22 15:45:43

RobertDyck and Impaler, while you are not in violation of forum rules you guys seem to have an excess of acrimony between you. It's my advice that you find a way to disagree more agreeably. Each of you clearly has a lot of knowledge and fair points which you're better off talking to each other about then insulting each other over.

Tom Kalbfus · 2014-12-23 19:33:48

RobS wrote:

The idea of big solar powered blimps is not new. The problem I see with this article is that it would be immensely difficult to get people from the Venus atmosphere back to orbit. The energy required is only a little less than to launch from the surface of the Earth to LEO. So, you want to put a Falcon 9 on the blimp? How will you refuel it? The blimp's mass would have to change by hundreds of tonnes, too, as the Falcon refueled (hydrogen is damn hard to extract from the Venus atmosphere) and then when you release the Falcon, its mass would instantly decrease by hundreds of tonnes. It would be easier to haul those hundreds of tonnes to low Venus orbit to provide shielding for an orbital station, which would be in a radiation environment not that different from ISS anyway. The astronauts would be 200 km up instead of 50 km, which wouldn't make that much difference to the science.

I think a mission to low Venus orbit should precede the first manned mission to Mars, The mission would be shorter, we could test out the transfer vehicle. I think the same transfer vehicle can be used for both planets. Getting out of the Venusian atmosphere would be a bitch. If we could have long duration balloons, we could use the same process Zubrin talked about to create our own fuel. Actually the hydrogen stored in a hydrogen balloon might be used as the feedstock for creating methane using solar power instead of a nuclear reactor. 75 degrees Celsius is a bit hot, I wouldn't want to step out into the Venusian atmosphere at that temperature without some protection and cooling. I think voice could be carried by sound, might be better that the sound will give some indication of who is talking to you and where he is, as opposed to a radio voice in your helmet. Probably the Venusian suit will have radiator fins to facilitate the suit's refrigerator, we would want to keep the internal suit temperature at around 15 degrees Celsius. The suit would also need to be light under Venusian gravity.

Impaler · 2014-12-23 20:34:38

I think Robert confuses my critique of his personal technology preference or an error on his part when trying to slap two technologies together and claiming it will have only the benefits of both and none of the drawbacks (the reverse is just as likely), with a 'can't be done' attitude. Missions and not technology development is the goal and I don't say that MISSIONS can never be done, I say that advanced technologies often do not provide enough improvement to justify their development for a mission, or in other instances when current technology is not practical for the mission I look for the easiest to develop tech that can do the job.

Back to the Venus mission. Specifically the decent to the surface by a cable. Steel will not cut it as it's breaking strength length under it's own weight is just 25km, fortunately Zylon and it's derivatives will do the job with a breaking lengths of ~380km, meaning a cable with the same mass as the cage would have a good safety margin. Zylon has the thermal resistance needed, but it will need a jacket to protect it from acid and UV which would be another plastic as their are many that will do the job.

Now the problem is to effectively moor the airship. The high wind speeds at the 50km altitude means their will be a huge drag force upon the ship. My back of the envelop estimates are ~650N per m^2 of the ships cross-sectional area, and this ship is likely to have BIG cross-section. As the mooring line descends into slower moving air it will act as a drag and begin to slow the ship down relative to the surface before it even contacts the surface, if we place a parachute on the cage then it will have a very high drag and will come down to very near the surface wind speeds so the final anchor being thrown out to catch the surface will only need to kill the final 2 m/s of surface wind speed for the cage and the airship. But their will be a lot of tension on the cable which has effectively become a mooring line now.

If the ship dose not counteract the lateral drag at it's altitude in some way then it will pivot on the mooring line and descend into thicker air which could destroy it thermally. Increasing the buoyancy of the airship would be the simplest solution. Running the engines is unlikely to generate enough force to cancel the wind, and if we let the wind instead spin the props we can get some more juice to send down the cable and supply the surface exploration. If the ship can generate lift from the air stream this will go a long way to reducing the need to drop ballast to get that lift, a lifting body shape for the blimp might be better then an ellipsoid. The ratio between the ships Net buoyancy+lift and the tensile force on the cable and the drag will determine the angle that the cable takes to the ground, if equal it will be a 45 degree angle and we would need a cable 70km long. It appears that the weight of the manned decent cage may actually be inconsequential compared to the tensile force to moor the air-ship, this might make the cable mass many times more then the cage and require a massive spool and winch.

I think it may be necessary to have a two stage inflation of the airship, an inertial inflation with Helium, then two 'saddle bags' along the sides of the main airbag can be inflated with processed atmospheric nitrogen, these would have a wing shape and when the ship is lowering the cable it will nose up to generate lift aerodynamically. The inflation would be gradual with some kind of pleating/accordion structure to get the wing segments to extend laterally a bit at a time and not flop around when half inflated. The extra buoyancy of the wings will be used to facilitate the ground exploration and to carry the weight of the gradually refueling return rocket.

RobertDyck · 2014-12-23 23:20:24

Venus balloon is lame. If you want to explore Venus, get yourself down to the surface. Venus has 90% gravity, so practically the same as Earth. Apollo landed on the Moon a spacecraft able to lift off from the surface, plus a descent/landing stage. That descent stage acted as launch pad for the ascent stage. If you want to use regular rockets, then lifting off from Venus will require this...

or this...

Then land a descent stage capable of landing that safely. And ensure propellent doesn't boil off on Venus. Good luck landing that.

Now understand why I talk about actual technology? And I do recommend the most practical technology that can do the job. Look again at the chemical alternative.

Last edited by RobertDyck (2014-12-25 09:25:01)

Tom Kalbfus · 2014-12-23 23:20:33

Impaler wrote:

I think Robert confuses my critique of his personal technology preference or an error on his part when trying to slap two technologies together and claiming it will have only the benefits of both and none of the drawbacks (the reverse is just as likely), with a 'can't be done' attitude. Missions and not technology development is the goal and I don't say that MISSIONS can never be done, I say that advanced technologies often do not provide enough improvement to justify their development for a mission, or in other instances when current technology is not practical for the mission I look for the easiest to develop tech that can do the job.

Back to the Venus mission. Specifically the decent to the surface by a cable. Steel will not cut it as it's breaking strength length under it's own weight is just 25km, fortunately Zylon and it's derivatives will do the job with a breaking lengths of ~380km, meaning a cable with the same mass as the cage would have a good safety margin. Zylon has the thermal resistance needed, but it will need a jacket to protect it from acid and UV which would be another plastic as their are many that will do the job.
Now the problem is to effectively moor the airship. The high wind speeds at the 50km altitude means their will be a huge drag force upon the ship. My back of the envelop estimates are ~650N per m^2 of the ships cross-sectional area, and this ship is likely to have BIG cross-section. As the mooring line descends into slower moving air it will act as a drag and begin to slow the ship down relative to the surface before it even contacts the surface, if we place a parachute on the cage then it will have a very high drag and will come down to very near the surface wind speeds so the final anchor being thrown out to catch the surface will only need to kill the final 2 m/s of surface wind speed for the cage and the airship. But their will be a lot of tension on the cable which has effectively become a mooring line now.
If the ship dose not counteract the lateral drag at it's altitude in some way then it will pivot on the mooring line and descend into thicker air which could destroy it thermally. Increasing the buoyancy of the airship would be the simplest solution. Running the engines is unlikely to generate enough force to cancel the wind, and if we let the wind instead spin the props we can get some more juice to send down the cable and supply the surface exploration. If the ship can generate lift from the air stream this will go a long way to reducing the need to drop ballast to get that lift, a lifting body shape for the blimp might be better then an ellipsoid. The ratio between the ships Net buoyancy+lift and the tensile force on the cable and the drag will determine the angle that the cable takes to the ground, if equal it will be a 45 degree angle and we would need a cable 70km long. It appears that the weight of the manned decent cage may actually be inconsequential compared to the tensile force to moor the air-ship, this might make the cable mass many times more then the cage and require a massive spool and winch.
I think it may be necessary to have a two stage inflation of the airship, an inertial inflation with Helium, then two 'saddle bags' along the sides of the main airbag can be inflated with processed atmospheric nitrogen, these would have a wing shape and when the ship is lowering the cable it will nose up to generate lift aerodynamically. The inflation would be gradual with some kind of pleating/accordion structure to get the wing segments to extend laterally a bit at a time and not flop around when half inflated. The extra buoyancy of the wings will be used to facilitate the ground exploration and to carry the weight of the gradually refueling return rocket.

You ever consider a kite, instead of a balloon? If you have a mooring line over a fixed position above the planet's surface, well the wind passing the object will effectively create aerodynamic lift, just as in an airplane, this is what keeps a kite in the air on a windy day. On Venus, you have super-rotating atmosphere that does a complete circuit around the planet every 100 hours. so imagine a base in a glider, there is no engine, just a 50 km long cable that is anchored to the ground.

Tom Kalbfus · 2014-12-23 23:29:00

RobertDyck wrote:

Venus balloon is lame. If you want to explore Venus, get yourself down to the surface. Venus has 90% gravity, so practically the same as Earth. Apollo landed on the Moon a spacecraft able to lift off from the surface, plus a descent/landing stage. That descent stage acted as launch pad for the ascent stage. If you want to use regular rockets, then lifting off from Venus will require this...
http://www.spacelaunchreport.com/sa202ps.jpg
or this...
http://upload.wikimedia.org/wikipedia/c … on_pad.jpg
Then land a descent stage capable of landing that safely. And ensure propellent doesn't boil off on Venus. Good luck landing that.
Now understand why I talk about actual technology? And I do recommend the most practical technology that can do the job. Look again at the chemical alternative.

Ever hear of the stratolauncher?
Screen-Shot-2014-12-02-at-4.07.02-PM.png
All we have to do is get a stratolauncher to Venus, that is how you get back into orbit.

RobertDyck · 2014-12-24 00:13:03

There are issues of entering Venus atmosphere with a stratolauncher aircraft. Without burning up. And aircraft fuel. And the rocket. And rocket propellant. This makes "Battlestar Galactica" from the 90-Day Report look small.

By the way, Stratolauncher was designed for Falcon 5. That would be a stage larger than Falcon 1, but smaller than Falcon 9, and with 5 engines. But SpaceX cancelled it. They said the only option is a Falcon 9 stage with only 5 engines. That's more weight. Stratolauncher was not designed for that much weight. I thought the company gave up at that point. Is this an old info-graphic, or does someone think they can build an even larger aircraft?

Tom Kalbfus · 2014-12-24 07:13:36

Well for one thing Stratolauncher was designed to get a rocket launcher off the ground, the Return Vehicle will never be on the ground, so most of that wing structure is unnecessary. I think a Venus Return Vehicle would consist of two parts, airplane and rocket. The airplane part holds the return rocket at altitude, it could be powered by Solar energy or a nuclear reactor, a Day on Venus lasts about 243 Earth days long, the day light portion is 121.5 Earthdays long. One possibility is that a nuclear powered jet airplane can hover over one spot above the planet's surface, by flying against Venus' superotating winds.

When the Venus Express spacecraft arrived at the planet in 2006, average cloud-top wind speeds between latitudes 50° on either side of the equator were clocked at roughly 186 mph (300 km/h). The results of two separate studies have revealed that these already remarkably rapid winds are becoming even faster, increasing to 249 mph (400 km/h) over the course of the mission.

http://www.astronomy.com/news-observing … g%20faster
So could a Solar powered airplane fly at 249 miles per hour or 400 km/h?
Here is an example of a Solar Powered Airplane

http://www.dailymail.co.uk/sciencetech/ … itely.html
A solar powered airplane like this will get twice as much solar power in the Venusian skies, there is also the matter of life support, which this airplane does not need when flying in Earth's atmosphere. I don't think a solar powered airplane can fly fast enough to counter the Venusian winds, unless it is flying at high latitudes, such as near the North Pole. To facilitate launches into space, you will want to fly the airplane in the direction of the wind, to reduce the cost of getting into orbit. I think a nuclear airplane is probably the way to go, because it can fly stationary over the surface for a long period of time, less than a Venusian day is all we need really The day portion of a Venusian day is 121.5 Earth days long. The probes on the surface probably won't last from sunrise to sunset anyway. The people onboard the airplane would control the rovers on the ground with a direct line of sight link as they hover in the atmosphere 50 km above. Balloons can't do this, only airplanes which can travel as fast as a commercial airliner can. Once the mission is over with, the crew gets onboard the rocket, which separates from the airplane and then blasts off for space. A manned mission to Venus will probably be a sprint mission, as the equipment won't last long enough to wait for the planets to realign. It probably is cheaper to have an unmanned airplane. The airplane's purpose is to store unmanned landers and rovers that are not yet ready to be used. Equipment doesn't last very long on the surface of Venus, so its easier to store them onboard an airplane, and then deploy them when the crew in orbit is ready to operate them. I think a smaller rocket might return limited surface samples to orbit, which then can be picked up in orbit by the manned craft and returned to Earth with the crew.

Impaler · 2014-12-24 21:35:40

RobertDyck wrote:

Venus balloon is lame. If you want to explore Venus, get yourself down to the surface. Venus has 90% gravity, so practically the same as Earth.

Except you ignored the MASSIVE drag that going through an atmosphere 92 times denser then Earths AND has a higher scale height nearly TWICE as much (15.9 to 8.5), that's going to add many kms to your DeltaV needs, I've seen estimates of as much as 20 kms higher http://hopsblog-hop.blogspot.com/2013/0 … v-map.html (meaning a TOTAL of ~30), take that with a grain of salt because it's a back of a napkin calculation from an amateur but it's clear that this drag effect completely swamps the slightly reduced Venus gravity well. If GW can give us a more accurate calculation that would be much appreciated. Also the rocket at launch is trying to operate in an atmosphere so dense that the exhaust gases barely expand at all, you will literally be working with naked combustion-chambers and that will be terrible for ISP and thrust. So either lots of staging, or some kind of extendable bell-nozzle or employing the airo-spike concept, this can let you keep ISP closer to full potential on the way up but theirs no physical way to overcome the bad expansion ratios. I won't even go into the difficulty of keeping a huge tank of cryogenic liquid from immediately boiling in a 600 C environment.

Chemical rocket assent from Venus surface is just not physically possible, floating in the atmosphere and beginning rocket assent from there looks to be the only option, and even that will require the rocket you pictured. The Delta-V profile from the airships ~50 km operating altitude (1 atmosphere pressure) is probably still higher then Earth assent delta-V because of the scale-height. So ideally the vehicle should drop all the crew-habitats, cable and basicly everything that is not the assent rocket (the crew got in the rocket before we did this just in case anyone was freaking out) and go up to as high an altitude as it can manage before detatching the rocket and going to orbit.

The cable+cage+umbilical-suit scenario is infinitely more practical AND it has the virtue of being reusable and re-positionable, so our intrepid Astronauts can make multiple visits to the surface over the course of the stay which could and should be several months to maximize scientific returns.

Tension on the mooring cable and if that cable mass can be practical without making the balloon ungodly large (buoyancy increases with the cube and drag with the square so just making the vehicle bigger is the simplest way to 'solve' the mooring problem). Alternatively moving to higher altitude may be a solution IF the total drag force is reduced by the thinner air faster then it is raised by the higher wind speed.

Tom: some kite like lift was what I was looking to generate with the inflated wing. But the vehicle overall still has to be a positive net buoyancy vehicle because it will not initially be moored to the surface. Balloons with lifting-shapes have been proposed and I think even built for use here on Earth, the portion of lift vs buoyancy I don't know and I suspect the vehicles are still designed to always be positively buoyant even without a bit of lift and I'd advocate the same thing. The aerodynamic lift would just be an augment when the vehicle moors to the surface which is just when it NEEDS it the most so it's very convenient in that sense.

I agree the solar-powered plane concept dose not look like it could ever achieve zero ground-speed because we can only just BARELY make such planes on Earth and their air-speeds are very very slow, doubling their available power from Venus solar won't bring the air-speed up remotely enough. The winds on Venus are circumnavigating the planet every 48 hours or so which means your getting a day-night cycle that is not too different from Earth not a continuous light unless you fly so fast as to have nearly zero ground-speed, it would be practical for a wide ranging aerial survey using downward pointing radar and line-towed sensors. Maybe the kite-lift methodology could be employed but that subjects the craft to some very intense air-speeds which would seem to rule out the gossamer type solar-powered-planes that we have now. The Nuclear aircraft (which would be prop not jet) seems to be the only viable air-craft method that could 'hover' over the ground.

Last edited by Impaler (2014-12-24 23:04:43)

Tom Kalbfus · 2014-12-24 23:29:34

Day and night aren't so important as exploring the planet's surface. My feeling is the exploration will occur on the day side of the planet and be finished before the Sun sets. I think probes would need to frequently lift off to dissipate heat. Probably not with rockets, but they could lift up like submarines. Lets say the probes have buoyancy tanks like a submarine. Inside the probe are tanks of compressed nitrogen, when the nitrogen is released into the buoyancy tanks, displacing the carbon-dioxide, the probe becomes lighter than the atmosphere and ascends from the surface, at a certain point the probe reaches the maximum altitude possible for buoyancy tanks and so inflates a balloon full of nitrogen, and lifts further. Nitrogen is a lifting gas all the way up to 50 km altitude. Now the airship will home in on its signal and intercept the balloon probe, unload its collection of rocks, and then prepare the probe for another mission to the Surface. The probe then descends back to the Venusian surface with heat sink to keep it cool while collecting choice samples through teleoperation. the advantage of a manned balloon as opposed to a space station in orbit, is that it is possible to reuse the probes a number of times before the Venusian environment eventually destroys them. I think a sprint mission with a Mars flyby would be preferable over the Holman transfer orbits that Zubrin talks about for his Mars mission. A long duration stay on Venus would be very difficult. I think for getting back into space, the optimum solution would be a suborbital docking between ascent stage and the mothership. the Mothership would need to transfer to a suborbital trajectory to match velocities with the ascent stage, dock with it and then use its engines to make it back into Orbit. Lets say for instance the Ascent Stage makes into space at half the orbital velocity, and the mothership slows to half the orbital velocity to intercept it, then it accelerates back into orbit. this will save some fuel mass for the ascent stage. Basically what Venus needs is a reverse shuttle, one that starts in orbit slows down to suborbit and then accelerates back into orbit before it enters the atmosphere. The ascent stage therefore will be much like SpaceShipTwo, it has to be out in space long enough for the mothership to dock with it and take it the rest of the way into orbit.

Impaler · 2014-12-25 01:27:54

I agree that each surface foray would be conducted on the day side of the planet.

I think probe dissipation of heat by rising is too slow to be effective, the heat-sink would be too massive and the great height difference in the atmosphere necessary to get to a cool environment means a very long transit time of hours as a buoyant craft can only rise at slow rate. Some combination of heat-resistant materials, insulation and active cooling seem more likely to me.

The reusable probes sound interesting, I'm not sure their is much need for internal buoyancy tanks if their are going to be external balloons in addition, seems it would be simpler to just use that for the whole buoyancy control process. Balloons made of Zylon and coated with acid-proof materials should be able to endure visits to the surface multiple times and be reused, it's more the rest of the probe that I would be worried about as it has so many more complex systems and computers on it.

The length of stay in the upper benign Venus atmosphere is going to be limited by just two things, life-support for crew with probably closing the water loop and food being main concerns (the same factors that are the limiters for Mars and any long duration human space-flight), and then the Acid problem. Gravity, Radiation, Energy, Mechanical stress on the air-frame and habit these will all be fine at the target altitude. So the trade off for duration is just Acid and that is a very well defined challenge that can be satisfied from a huge knowledge base of material science, coatings of thin flexible fiber glass are very likely to be sufficient. Rather it is the return to space and the surface access that present the major hurdles. I think we can easily make something which will survive the whole synodic period of occupation by crew which looks to be around 300 days (assumes 120 days to and from Venus), a permanent habitat is another story.

Last edited by Impaler (2014-12-25 02:57:37)

Tom Kalbfus · 2014-12-25 08:40:16

Impaler wrote:

I agree that each surface foray would be conducted on the day side of the planet.
I think probe dissipation of heat by rising is too slow to be effective, the heat-sink would be too massive and the great height difference in the atmosphere necessary to get to a cool environment means a very long transit time of hours as a buoyant craft can only rise at slow rate. Some combination of heat-resistant materials, insulation and active cooling seem more likely to me.
The reusable probes sound interesting, I'm not sure their is much need for internal buoyancy tanks if their are going to be external balloons in addition, seems it would be simpler to just use that for the whole buoyancy control process. Balloons made of Zylon and coated with acid-proof materials should be able to endure visits to the surface multiple times and be reused, it's more the rest of the probe that I would be worried about as it has so many more complex systems and computers on it.
The length of stay in the upper benign Venus atmosphere is going to be limited by just two things, life-support for crew with probably closing the water loop and food being main concerns (the same factors that are the limiters for Mars and any long duration human space-flight), and then the Acid problem. Gravity, Radiation, Energy, Mechanical stress on the air-frame and habit these will all be fine at the target altitude. So the trade off for duration is just Acid and that is a very well defined challenge that can be satisfied from a huge knowledge base of material science, coatings of thin flexible fiber glass are very likely to be sufficient. Rather it is the return to space and the surface access that present the major hurdles. I think we can easily make something which will survive the whole synodic period of occupation by crew which looks to be around 300 days (assumes 120 days to and from Venus), a permanent habitat is another story.

You think food can be grown at altitude? A Venus Base would look strange compared to a Mars Base. I think the idea behind a Venus Base would be to put a laboratory within the Venus atmosphere for examining Venus rocks and soil samples, and then return the data to Earth. The return to orbit ships would be used mostly for the astronauts, and perhaps a select bit of Venusian rocks that would be returned to Earth for the museums. A think the return vehicle would be a suborbiter, which the mothership would meet halfway in space. A space docking like this would have little room for error! I think a suborbiter would spend about 15 to 20 minutes above the atmosphere, much like an ICBM warhead, if not docked with, it will reenter the Venusian Atmosphere, so another ship would have to meet it half way and boost it the rest of the way to orbit. This way, you get to build a smaller return vehicle, it does not have to reach full orbital velocity. the orbital velocity for Low Venusian Orbit is 7.151746948 km/sec the orbital velocity for Mars is 3.404178775 km/sec.

So lets say the Venusian Ascent stage can reach a suborbital velocity of 3.7 km/sec, it would be built much like a Mars ascent stage, so it would be of similar mass. So basically it sends astronauts on a parabolic trajectory and something from Orbit will have to slow down from orbit by the same amount to meet it. the advantage here is the vehicle that slows down and speeds up remains in space at all times, we don't have to float its entire Mass in the Venusian Atmosphere, leaving it in orbit until needed has advantages. What do you think of this idea. Naturally we aren't going to do this from Earth orbit, as we have sufficient infrastructure on Earth, but Venus has no infrastructure.
th?id=HN.608032825373230913&w=103&h=103&c=8&pid=3.1&qlt=90&rm=2
The top part of this could be tethered to a balloon and kept ready for partial return to Low Venusian Orbit, part of the Mothership would likely detach to intercept and dock with it, both on the downward portion of their trajectory, the intercept craft would have to light its engines to boost the combination to orbit.

Last edited by Tom Kalbfus (2014-12-25 08:49:17)

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