PakledHostage

I agree. Just be yourself and keep looking. Eventually you'll find someone who accepts you for who you are.

Every year after the Academy Awards nominees are announced, I make a point of trying to watch as many of the films as I can that I haven't yet seen. This evening, I watched the documentary "Virunga". I would be interested to know what people think. (Ideally without getting into the political issues that it raises.) I thought that it was extremely well done. It had a compelling story and beautiful cinematography. I hope that its nomination draws attention to the need to protect the UNESCO World Heritage Site of Virunga, despite it being located in such a politically volatile part of the world.

Please re-read my post... And in case you have difficulty with comprehension, I was responding to TheGatesofLogic who focused on the fact that Plutonium-238 isn't fissile. I pointed out that, while it may not be fissile, it is still dangerous. Not only because it is radioactive, but becase it is also a toxic heavy metal. It is restricted by rigorous regulations for a reason.

I am not trying to pick nits here... Only trying to clarify something about the metric system for our imperial system using friends: You are basically correct, but your use of units is a bit cringe inducing... Pressure in the metric system is measured in Pascals. Standard air pressure at sea level and 15°C is 101325 Pascals. Pascals have units of Newtons per square metre. A Newton is a unit of force. It has units of kg * m/s2. When you write pressure in terms of kg per cm2, as you did, you are effectively using mass and weight interchangeably. I'm sure you'll agree that that's not cool on a science forum!

Well, the Oscar nominations were announced today. Interstellar received nominations in the following five categories: Music Production Design Sound Editing Sound Mixing Visual Effects I note the distinct lack of nominations for Best Picture, Best Screenplay or even Cinematography... That doesn't surprise me because I think this movie was a over-hyped, but it may surprise some reading this in light of how Gravity did last year. I think Interstellar was better than Gravity. Edit: Interestingly, Guardians of the Galaxy was also nominated in two categories: "Visual Effects" and "Makeup & Hairstyling".

What kind of question is that? Lots of people might ask "who cares about Venus?" while you obviously care a lot about it. You may not understand their differing interests from your own, but they have just as much right to them as you do to yours.

Sorry, but can I drag us back to the original topic of discussion? The question was whether or not "any future manned spacecraft that goes to Mars [will] use aerobraking to save delta-V for circularising or is it far too risky/requires too much added weight for heatshields?". The issue of landing on Mars is irrelevant other than in response to another question about whether or not aerocapture had ever been used in the past. If you define aerocapture to include direct entry to a landing, then yes it has. Aerocapture has, to my knowledge, not yet been used to enter Mars orbit; only propulsive capture coupled with aerobraking has been used. The paper I cited above seems to suggest that the relative risks of aerocapture are acceptable, should they ever be employed on a Mars sample return mission. A Mars sample return mission would be significantly larger and more massive than any other mission we've sent to Mars in the past, yet the paper's authors believe that aerocapture can be done with comparable reliability to propulsive capture and to a combination of propulsive capture and aerobraking. The paper also says the following about navigation targeting: It stands to reason that, since aerocapture into Mars orbit is a reasonable approach for a Mars sample return mission, it would also be a reasonable approach to entering orbit for a manned mission. As KerikBalm pointed out, we're only talking about scrubbing on the order of 500-1000 m/s from our arrival speed of 5400 m/s - 5900 m/s. That represents an energy dissipation (per kilogram) of roughly 10-20% of that required during reentry from LEO. Even considering the different heat transfer characteristics of Mars' CO2 atmosphere compared to Earth's mostly Nitrogen and Oxygen atmosphere, it isn't beyond our current technological limits to pull it off. Likewise, it stands to reason that it wouldn't be beyond our technological capabilities to use Aerocapture to enter Mars orbit during a manned mission.

No, but machines can survive in places we can't very readily. A hyper-intelligent AI would be capable of utilizing different infrastructure than we can for that reason. They may compete with us for available land and resources, or they could just bugger off and go somewhere else where they won't need to compete with us. Either way, it will affect the infrastructure that is available to us and that we will have to work around.

The wild card that nobody has mentioned yet is true machine intelligence. Nobody can say what will happen if we ever develop true AIs. They may keep us as pets, they may cohabitate this planet with its existing biological beings, or they may just bugger off and expand into the solar system and beyond. It is anybody's guess. No matter what, the implications on what the world will be like in 1000 years will be huge.

Like back on page 10 of this very thread?

I think the idea is that it could be used in a dirty bomb. In addition to being radioactive, Plutonium is a toxic heavy metal. The risk would, of course, depend on how much radioactive material the pacemaker contains.

You keep citing that value (6.9 km/s) but where do you get it from? The atmosphere relative entry speeds anticipated for Mars Science Lab were only about 5.4 - 5.9 km/s, depending on the timing of the transfer from Earth. (ref: Mars Science Laboratory Mission Design Overview, Table 1 and Table 2). As you point out, MSL did not execute propulsive braking before it entered Mars atmosphere directly. Edit: I recalled reading a paper that compared the relative risks of aerocapture vs. propulsive capture for Mars orbiters. I found it after a brief search on Google. It is titled "Assessing the Relative Risk of Aerocapture Using Probabilistic Risk Assessment". It was published by The American Institute of Aeronautics and Astronautics. There's no date on the .PDF copy of the article but it seems to have been published in about 2005. The article uses as a case study, a Mars Sample Return mission that was under investigation at the Jet Propulsion Laboratory (JPL) at the time. I mention it because it might be interesting reading for some here.

Also, Argylas' question was "will any future manned spacecraft that goes to Mars use aerobraking to save delta-V for circularising". That doesn't preclude some combination of propulsive capture and aerobraking to save delta-V.

It may be that high for some spacecraft, but the atmosphere relative entry speeds anticipated for Mars Science Lab were only about 5.4 - 5.9 km/s, depending on the timing of the transfer from Earth. (ref: Mars Science Laboratory Mission Design Overview, Table 1 and Table 2). That's only about 3/4 that of reentry from LEO, despite the fact that MSL entered directly from an Earth-Mars transfer trajectory (i.e. it did not enter Mars orbit first). It depends on whether or not you restrict the definition of aerocapture to mean capture into orbit, or if you allow it to include direct atmospheric entry to a landing. The Mars Pathfinder mission used direct entry to a landing back in 1997, as did the Mars Exploration Rover missions and the Mars Science Lab mission. As Nibb pointed out, other Mars orbiter missions have used propulsive capture followed by several months of aerobraking to reach their final working orbits.

Maybe BECAUSE you play KSP with its conspicuous lack of re-entry heat?

But that amounts to curing the symptoms, not the disease.

They may well control the barge's lateral position using thrusters. They can't control the vertical position of the deck that way, however. That is the point that people are speculating about. The deck's vertical position is governed by the waves because the barge is floating on them. Some multihull vessels actively damp the up/down motion by modulating buoyancy, but SpaceX's barge is not a multihull vessel with that capability.

This is a good idea but you'd have to consider the stability of the barge. The hydraulically actuated platform would be very heavy. Heavy structure mounted high above the centre of buoyancy is desabalizing. Especially if it is moving around. That doesn't mean you can't do it, but it may be cost prohibitive to design around it.

Was I the only one who couldn't help but think of Kent Brockman's infamous ants upon seeing those fuel droplets in zero g?

Just checking in. Middle of the night here but I got up to watch the YouTube stream on the TV. Range green!

Maybe you need to get out more? Just sayin'

I just stumbled across this and thought I would share it: An animation of Rosetta's route from Earth to Churyumov-Gerasimenko in Solar System Scope.

By my read, NERVAfan was speaking about a hypothetical future mission, not about New Horizons. I understood that his point was made in response to GigaG's comment about the viability of doing so on some hypothetical future mission. IIRC, New Horizons has already been re-targeted to flyby Pluto at a greater distance than first planned because they are worried about the amount of debris in orbit about Pluto. They don't want to hit any of it and destroy the probe on their way by.

Maybe you saw it via the link in this thread?

The US Government's Accountability Office has issued a Statement on Sierra Nevada Bid Protest Decision. P.S. Sorry in advance if I offended anyone by necroing this thread, but I thought it better to post here rather than start a new one.