Delta V for venus orbit from the average ground level (0 AGL)

[Vaporized Steel]

I've been wondering about this for quite some time now but I lack the mathematics, reading sources or just the answer to this question anywhere out there so I thought let's ask it right here.

Let's just assume we can get a probe (or manned lander for your imagination) to the surface of venus. Taking into account that it would probably be a heavy craft as it would need to carry the protective titanium(other material), corrosive and atmospheric pressure shielding and the setup of instrument coolant. Albeit a coolant system to cool a already overheating engine nozzle that would only heat further when fired upon. And include any of the other obstacles I didn't yet mention to be solved making the scenario completely hypothetical ofcourse.

What I would like to know is how much Delta V would it cost such a craft from the average venusian ground level to reach low venus orbit?

Feel free to use the topic to discuss any of the scientific obstacles that would be involved to make it happen.

[Ralathon]

Venus is almost as big as the Earth, so the default dV needed will be about the same. Venus rotates very slowly compared to earth, so slowly that a venusian year actually takes longer than a venusian day. This means that the slightly lesser gravity is roughly compensated by the 300ish m/s we can leech from the earth's rotation and the denser atmosphere (Although atmospheres have surprisingly little dV impacts, its only about 3% here on earth).

So I'd say around 9.3 km/s for a venus orbit. Or at least within that neighborhood.

[Vaporized Steel]

Euhm.

Atmosphere have little delta V impact?

Euhm... venus has a surface pressure of 92times that of earth. Where it exponentially fades into equally earth like pressures at 50km up. So while a ascending rocket would need TWR to escape venus gravity it has to maintain a ascend velocity of perhaps 2-4dozen m/s in the lower venusian atmosphere for many minutes because the atmosphere slows it down resulting into huge atmospheric delta V requirements and quite frankly I expected the answer to be in the tens of thousands.

Either I'm delusional about things here or you forgot to take venus atmosphere into account. I mean the same reason why you would need 11.5-12km/s of delta v to orbit eve is because you spend atmospheric delta V to ascend through the atmosphere.

[cantab]

This map suggests 27 km/s.

http://i.imgur.com/SqdzxzF.png

Comments thread: http://www.reddit.com/r/space/comments/1ktjfi/deltav_map_of_the_solar_system/

I don't know how the figure was calculated but it seems plausible. Although real atmospheres aren't as soupy as in stock KSP, Venus's surface pressure is 92 times Earth's; compare that to Eve's surface pressure which is only a few times Kerbin's.

The delta-V and for that matter TWR needed to reach Venus orbit is about the same as to reach Jool orbit from its surface; I wouldn't be too surprised if this was deliberate on the part of Squad.

[Ralathon]

Euhm.

Atmosphere have little delta V impact?

Euhm... venus has a surface pressure of 92times that of earth. Where it exponentially fades into equally earth like pressures at 50km up. So while a ascending rocket would need TWR to escape venus gravity it has to maintain a ascend velocity of perhaps 2-4dozen m/s in the lower venusian atmosphere for many minutes because the atmosphere slows it down resulting into huge atmospheric delta V requirements and quite frankly I expected the answer to be in the tens of thousands.

Either I'm delusional about things here or you forgot to take venus atmosphere into account. I mean the same reason why you would need 11.5-12km/s of delta v to orbit eve is because you spend atmospheric delta V to ascend through the atmosphere.

Yea, but KSP's atmospheric model is about as accurate as the geocentric model: Real atmospheres do not behave like soup. You'd have to deal with a lot more drag and dynamic pressure obviously. But you can engineer around those.

If you can pick between a fragile rocket that slowly climbs and thus needs 20k dV or a sturdy rocket that quickly climbs for 11k dV then engineers are likely to just build a sturdier rocket. We know how to build things that can withstand ridiculous dynamic pressures, ICBM warheads are a good example of that.

[maccollo]

This map suggests 27 km/s.

My Venus lander in RSS does it with 16 km/s, but it varies a lot based on your terminal velocity during the cruise stage. With a very large rocket you can get an initial terminal velocity around 150 m/s, and then you have 10 minutes of very very max Q.

This obviously ignores the the pressure and temperature. Can you even make a rocket engine that works at 92 bar?

Also the rocket would have to be extremely sturdy to be able to withstand aerodynamic forces.

Then there's the problem of temperature (400 C, day and night), which will weaken the structural integrity of your rocket, aswell as a host of other issues.

[andrewas]

Thats a bit of an understatement. Every fuel I know of boils well below that temperature. Many metals are softened, plastics don't exist, virtually everything behaves differently than it does on Earth. Just building a rocket on Earth and not having it break due to thermal expansion on Venus would be a challenge. Oh, and then there's the acid, which restricts which materials you can use.

One solution may be to have the ascent stage hover using balloons, and dedicated landers (helicopters?) are the only things to touch the surface. Yes, this is an insane plan, but it might work on Venus.

[Vaporized Steel]

That's an idea I had actually. Dropping pressurized nitrogen/hydrogen tanks to the venusian surface and then find some fabricated sillicon matterial from which you can build large balloons to lift ascend stages. Also solves the problem of cooking fuels as any fueled reaction engines are not needed in the large hotter parts of the atmosphere.

@Cantab

I'm very willing to know how they come up with that number. Anyone?

But then again Macollo stated he did 16km/s on venus in RSS.

I agree that KSP is bad at some parts of the physics spectrum. Presumably how it calculates drag and pressures of atmosphere or more notoriously water for that matter.

I can't be sure if one estimate is based on a game with a realism overhaul mod. When there is a real life chart online saying it costs 27km/s. Either the real solar system / realism overhaul mod isn't 100% realistic in this respect. Or the online real life delta V chart is innacurate.

Edited May 19, 2014 by Vaporized Steel

[Idobox]

Thats a bit of an understatement. Every fuel I know of boils well below that temperature. Many metals are softened, plastics don't exist, virtually everything behaves differently than it does on Earth. Just building a rocket on Earth and not having it break due to thermal expansion on Venus would be a challenge. Oh, and then there's the acid, which restricts which materials you can use.

One solution may be to have the ascent stage hover using balloons, and dedicated landers (helicopters?) are the only things to touch the surface. Yes, this is an insane plan, but it might work on Venus.

It's not that bad. There are several hydrocarbons that would still be liquid at these temperatures (heavy fuel, or even tar basically), you could also use liquid metal, or solids like graphite. The oxydizer, on the other hand, will be a problem. Potassium perchlorate melts at 525°C and decomposes at 600°C, so it could work, although it's not very good for a rocket. I imagine either a SRB or a hybrid rocket with solid oxidizer and liquid fuel.

For construction materials, titanium can perfectly do the job. It's expensive and difficult to work with, but it is superior to steel and aluminium as a structural material. Ceramics and things like graphite or silicon carbide will keep working easily. For electronics, silicon carbide is the substrate of choice too.

And the easiest way would be to take advantage of the atmosphere, using either ramjets or ducted rockets to get through the thickest part of the atmosphere. You don't get oxidizer as you do on Earth, but you still get a lot of reaction mass to improve your ISP.

[Idobox]

I just thought of something, Venus Atmosphere is choke full of CO2. Although it is a very bad fuel, it is possible to use it as oxidizer with things like H2, Al, AlH3 and Mg.

And it just so happens people looked into it, and I found a paper talking about it for Mars, but also talking of Venus

http://www.lpi.usra.edu/meetings/roundtable2006/pdf/shafirovich.pdf?origin=publication_detail

It basically says you can get 200s ISP for Al or Mg + CO2 rocket, turbojets are a bad idea because of solid particles damaging the blades but these people are still working on it http://www.wickmanspacecraft.com/marsjet.html, and ramjets would work if you somehow managed to get the craft to proper speed.

And because it's Venus, a eutectic alloy of Aluminium and Magnesium would be liquid on the surface (710K vs 730K), and could be kept liquid by recycling combustion heat or atmospheric friction while climbing, allowing for "simple" liquid fuel design. Solid fuel ramjets with aluminium powder are also an option.

[AngelLestat]

Try to raise from venus surfuce using any kind of rocket or ramjet propulsion would be almost as silly like try to launch a rocket from 300 meters deep in our oceans.

Of course the first step to solve this problem would be float. The same in venus.

You can reach 50km or 70 km of height before ignite your engines and start to burn fuel like crazy.

I would said 8,5km/s of delta-V, becouse venus gravity as its diameter are lower than earth.

[Red Iron Crown]

It would seem like a balloon would be the way to go for the early ascent, if one could be made to survive the conditions.