2020 era Orion CEV in Venus orbiter mission

[gunsandrockets]

I was looking again at the NASA document of the Venus orbiter mission more closely to understand why the Mars equivalent mission used so much more delta V (and therefore was 70% more massive!).<br /><br />The Venus mission trip time total is 565 days, with a 40 day stay at Venus. The Mars mission trip time total is 451 days, with a 20 day stay at Mars.<br /><br />The total delta V to depart Earth and brake at the destination planets are almost identical. It's the return delta V that really hurts the Mars mission, almost 2 km/s higher for the Mars mission than the Venus mission. That's where the real difference lies.<br /><br />I see now that for the Mars mission to have a trip time similar to the Venus mission, the Mars mission uses higher delta V to compensate for Mars being out of ideal position relative to Earth. If the stay at Mars was longer by 17 months(!), then no doubt the higher delta V of the Mars orbiter mission would no longer be neccessary. But that would double the total Mars mission trip time from 451 days up to about 900 days!<br /><br />So in a way you were right, and you were wrong. To go from LEO to high Venus orbit and back is about the same delta V as travelling from LEO to high Mars orbit and back under ideal conditions. But to conduct the same kind of Mars orbiter mission as the Venus orbiter mission, the Mars vehicle would be much more massive and use much higher delta V than a Venus vehicle, so astronautix was right too.

 

[gunsandrockets]

"I'm with BDE and Dragon04: I don't think the marginal benefits of an manned orbital mission to Venus would be worth the cost, not even for real-time control of surface probes...I'd rather see the money used to develop either long-lived surface probes, or lots and lots of cheap, short-lived--but reliable--probes. Either would negate the importance of a manned orbital mission, in my op." <br /><br /><br />What size fleet of fully autonomous robotic probes would it take to achieve results equal to a combined manned/unmanned mission? I believe it would be more expensive to acquire the same science using purely unmanned methods.<br /><br />"For instance, if there is no significant improvement in technology that would enable a probe to survive on Venus for more than a few hours, data in real-time would provide little advantage over traditional remote unmanned probes, especially since in the final analysis the light-travel delay is the same from a terrestrial perspective."<br /><br />It's because of the short survival time of Venus probes that real-time control (which is only possible from a short distance away) is so valuable. All that an autonomous probe could do is follow it's preprogrammed routine and perhaps completely bypass something that is of vital interest while focusing only on what it was already expected to find.<br /><br />If you really believe that autonomous probes are that much more cost-effective than real-time manned control, than you must also accept that purely unmanned exploration is most cost-effective for ALL space exploration, not just for a Venus orbiter mission. If that is the case how could you object to those who argue for shutting down manned spaceflight altogether?<br /><br />"To be fair, I'd support a Venus flyby mission as a kind of "because it's there" adventure to stoke up interest in a woefully neglected planet. But for the near term (20-30 years), I'd rather see some NEO landing missions."<br /><br />Why not both NEO and Venus missions?<br /><br />

 

[mithridates]

I just remembered something else that would further justify sending people - a while ago I started a thread on sending a probe to the mountaintops of Venus, somewhere in Maxwell Montes which is up to 11 km above the surface where the temperature is somewhat below 400 degrees and the pressure under 50 bars, which is half that on the surface. The problem with that would be actually landing a probe, because it would have to do everything itself. Sending people in to take care of the task though would take care of the problem. The atmospheric density alone would make it quite easy to pilot the probe into the right position and there are a lot of places to send it to land:<br />http://www.lpi.usra.edu/publications/slidesets/venus/slide_15.html<br /><br />I was considering anywhere in Ishtar Terra to make it easy for a probe to land by itself, but if people are there to supervise the flight there's no reason why we can't aim for some of the highest points on the planet. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[gunsandrockets]

"...I was considering anywhere in Ishtar Terra to make it easy for a probe to land by itself, but if people are there to supervise the flight there's no reason why we can't aim for some of the highest points on the planet" <br /><br />Excellent excellent point! I should have thought of this important point myself.<br /><br />Real-time control of an unmanned lander allows landing in regions that are off-limits due to high risk. And of course the most interesting places on a planet are usually the most dangerous places to land.

 

[willpittenger]

My impression was that the CEV missions to Venus would be mainly a flyby. One with a long time in the area perhaps, but a flyby would not require fuel to enter or leave Venusian orbit. Your time there is limited, but the time people could spend (even in a big CEV with just 2 or 3 crew) in a small capsule would be limited. The CEV would be along only for reentry purposes once you get back home if you expect to enter Venusian orbit. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p>Venus has very high levels of sunlight compared to Earth, making a solar powered aircraft that could in theory fly indefinitely much easier to design.<p><hr /></p></p></blockquote><br />What about wind speeds at those altitudes? Because of Venus rotation being, well, weird, winds can really blow. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[willpittenger]

What would a CEV need to fly a RADAR to Venus or an NEO? In both cases, a RADAR with a trained operator right there could quickly get data that would be missed via other means. At Venus, we could fill in gaps in the Magellan data or answer questions left unanswered (like what those domes are). At a NEO, we could get a picture of its interior structure. Without a close-up RADAR, could we get a accurate mass estimate? <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[mithridates]

I think they proposed a really eccentric orbit so that it would be easy to break away from the planet when necessary. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[JonClarke]

"So in a way you were right, and you were wrong. To go from LEO to high Venus orbit and back is about the same delta V as travelling from LEO to high Mars orbit and back under ideal conditions. But to conduct the same kind of Mars orbiter mission as the Venus orbiter mission, the Mars vehicle would be much more massive and use much higher delta V than a Venus vehicle, so astronautix was right too.'<br /><br />My source was using a one figure covers all approach. So it does not surprise me that there would be a range of values covering different missions.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

"My impression was that the CEV missions to Venus would be mainly a flyby. One with a long time in the area perhaps, but a flyby would not require fuel to enter or leave Venusian orbit. Your time there is limited, but the time people could spend (even in a big CEV with just 2 or 3 crew) in a small capsule would be limited. The CEV would be along only for reentry purposes once you get back home if you expect to enter Venusian orbit."<br /><br />Why do assume that the crew would spend the entire mission in the CEV. The CEV is just the ferry. They would spend most of the mission in a much larger mission module. <br /><br />This has been pointed out so many times in conjunction with Mars, asteroid and Venus missions with the CEV that its not funny. But people still keep making this basic mistake.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

"What about wind speeds at those altitudes? Because of Venus rotation being, well, weird, winds can really blow. "<br /><br />I would assuem that less turbulent zones could be targeted. Also remember that because the atmosphere of Venus is quite tense, the aspect ratio of any aircraft can be quite low and therefore easily built to withstand turbulence.<br /><br />the exception would be if they were solar powevered 9remember helios?. But even here, with solar intensties 2.6 times earth the wing area can be much smaller. Assuming the same chord, a 2.6 reduction of wing area results in a wing span of only 38%.<br /><br />However, light intensties are much lower below the cloud deck. Here would would need chemical fuel I suspect, although the solar intensity is still higher than Mars so provide turbulence is low solar aircraft might still be possible.<br /><br />Landis et al paper<br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[mithridates]

If that's the paper I'm thinking of, he proposes a craft that stays aloft at an altitude of about 65 km or so where the atmospheric pressure and sunlight is at the level that it can stay up for as long as it wants, and after charging its batteries it will dip down to about a 40 km altitude for short periods of time, then rise up on its own power going against the wind until it has retained its former altitude and can recharge again.<br /><br />What I'm not quite certain about is what can be seen at that altitude? It would be really interesting if a solar flyer could be equipped with about a dozen tiny 'bomblets', small probes that would be dropped from its wings one at a time that would fall to the surface and take measurements a la Venera for about an hour or so. Really small probes, maybe only about 25 cm in diameter or so. With the solar flyer right there there wouldn't be any need for a signal strength that could reach all the way back to Earth, just 60 km up to where the flyer is. These could be dropped once every few days or so at places of special scientific interest. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[JonClarke]

They called dropsondes, and are used by hurricane-chasing meteorlogical aircraft.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[mithridates]

Ah, a word meshed together from English and French. Does making them for a Venus mission of this type sound feasible? I'm never at a loss for ideas but rarely are they ever practical. Maybe this time I've lucked out.<br /><br />Looking at the image here:<br />http://en.wikipedia.org/wiki/Imageropsonde.gif<br />It would be nice to have a more spherical one with a weighted gyroscope inside to always keep the cameras pointing in the desired direction regardless of how it falls. I wonder how long one could be made to stay cool for? <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[gunsandrockets]

"I'm never at a loss for ideas but rarely are they ever practical. Maybe this time I've lucked out." <br /><br /> I mentioned a similar idea to yours much earlier in the thread here...<br /><br />http://uplink.space.com/showthreaded.php?Cat=&Board=missions&Number=662780&page=0&view=collapsed&sb=5&o=0<br /><br />[A flying probe could quickly cover large areas of Venus, and circle those spots most interesting. The flying probe might even carry one or more landers or 'lawn darts' to drop on a particularly interesting location for direct measurement of the surface.]<br /><br /><br />"Looking at the image here: <br />http://en.wikipedia.org/wiki/Imageropsonde.gif <br />It would be nice to have a more spherical one with a weighted gyroscope inside to always keep the cameras pointing in the desired direction regardless of how it falls. I wonder how long one could be made to stay cool for?"<br /><br />I don't have much hope for the longevity of small probes. Too much surface area to absorb heat compared to the mass of the probe. The lifetime probably will be measured by the time it takes for whatever refrigerant is used to boil off. That probably means a very rapid descent to the surface, meaning a dartlike profile.<br /><br />

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p>Why do assume that the crew would spend the entire mission in the CEV. The CEV is just the ferry. They would spend most of the mission in a much larger mission module.<p><hr /></p></p></blockquote><br />Doesn't matter. You are effectively saying that the CEV will be used only for the ride into space and the reentry when you get home. Other than those two (important) parts, why have a CEV (and its service module) along for the entire ride? What does it offer? Would it make more sense to have a dedicated propulsion system specific to the mission? You would need to actually reenter orbit at Earth to get back into the CEV for the trip home, but the CEV is going to require that we send several extra tons to Venus. Might as well make that fuel. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p>However, light intensties are much lower below the cloud deck. Here would would need chemical fuel I suspect, although the solar intensity is still higher than Mars so provide turbulence is low solar aircraft might still be possible.<p><hr /></p></p></blockquote><br />Descending brings back the pressure and temperature problems. Also, the clouds are where the acidic content is likely to be highest. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[JonClarke]

You take the CEV along because it simplifies the misison profile. One rendezvous with the mission module at the start of the mission (assuming the CEV is launched separately, and you you can use the atmosphere to brake with on your return.<br /><br />Otherwise when you return you have to brake your entire mission module into Earth orbit and wait for a whole new CEV to be launched and renezvous with you. Not only is the braking maneuver likely cost more propellant than taking a stripped dowen CEV to Venus (or Mars) and back, you need an additional launch and rendezvous and mission critical orbital insertion burn.<br /><br />Jon<br /><br /> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[willpittenger]

If so, we may need interim flyby missions that settle for a minimal science mission to prove that humans will last that long that far from Earth. How many missions do we have away from LEO (as defined by the STS limits) have more endurance than two weeks? Yet this one requires a year? <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[JonClarke]

I have al;ways been a bit sceptical about planetary flyby missions because of the scientific return on cost. But a case can be made from a development point of view, I guess.<br /><br />I have no idea how long a Venus flyby would take. It would depend on the orbit. Mars ones, for example can be as short as 400 days or as long as 690 days. But for obvious reasons there has been much less research into manned mission to venus as opposed to Mars.<br /><br />if you wanted deep space missions of less than a year then there are the NEOs, as discussed in the other thread. <br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[gunsandrockets]

"I have no idea how long a Venus flyby would take."<br /><br />About one year.<br /><br />Earlier in this thread under the subject 'Venus flyby mission' ...<br /><br /><br />http://uplink.space.com/showthreaded.php?Cat=&Board=missions&Number=664989&page=0&view=collapsed&sb=5&o=0<br /><br />...I posted links to a description of a Venus flyby mission using modified Apollo hardware.

 

[mithridates]

This isn't really related to any proposed missions in the near future but since we're talking about Venus I might as well bring this up in this thread because I'm curious if there's anything physically impossible about this besides our inability to carry it out. What would happen if an airtight tube were built on the ground with a hole on the bottom and another 50 km up? I assume that like on an airplane when people use a tube to scatter ashes from an urn, the air would be sucked upward to where the pressure is lower. Since the planet is hot due to the inability of heat to escape the thick clouds, would bypassing them in this way on a massive scale cool off the planet? <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[mithridates]

Ah, I think I see why - the difference in the atmosphere is too gradual all the way up. Gotcha. However, the winds up there are 300 kph and it should be easy enough to have them rotate a fan located on the top to bring the air up I assume. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p>I have al;ways been a bit sceptical about planetary flyby missions because of the scientific return on cost. But a case can be made from a development point of view, I guess.<p><hr /></p></p></blockquote><br />One example of that would be Mariner 9. Until then, Martian missions had gathered only a handful of shots that many probably thought came from the Moon. However, I doubt Mariner 9 could have succeeded until its predecessor's proved they could reach Mars. I should also note the mission profile for New Horizons. All things being equal, I would rather have an orbiter. But how do we stop unless we settle for a trip that could last more than a decade?<br /><br /><br />Back to the Venus topic, figures we would need so much time. I guess an NEO mission will have to prove the endurance part. Once we go to Venus, we might as well enter orbit. Sounds like the trip won't take any longer or require much more Delta V.<br /><br />For the "prove the endurance flyby" you just shot down, I think I was thinking mainly of a trip where we could take shortcuts to get there faster. But I realize now that we have no way to generate that much Delta V.<br /><br /><i>Conversation via subspace to Captain Kirk</i><br /><br />Us: <font color="blue">Captain, we have a bunch of scientists trying to get to Venus to study it up close. The best vehicles they have require a round trip of more than a year in microgravity. You could make the trip in a few hours. Could you give them a lift?</font><br /><br />Captain Kirk: <font color="yellow">Sorry. That would be a violation of the Prime Directive. We can't help you out at this time.</font><br /><br />Us: <font color="blue">Rats.</font>/safety_wrapper> <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[JonClarke]

Thanks, I had seen that but could not remember where. The original source for the article says 360-400 days.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>