* The surface atmosphere density is higher than Earth's (1.5 atm)
* Gravitational force is much lower (0.15g)
* We don't know a lot about the surface composition or topography, so wheels and motors represent a challenge
* Visibility may be poor, making visual navigation tricky (though that's also a problem for a flying vehicle I suppose)
I've heard people ask about "why a nuclear power source?" Saturn is 10x as far from the sun as Earth, so sunlight is about 1/100th as bright. In addition, Titan's atmosphere blocks most of that. There really isn't any other realistic option.
I hope it works and they take videos.
Conversely, on Titan, we won't need to worry about heat sinks as everything is kept at ~94K in a bath of liquid and frozen methane. Perhaps in a few hundred years AWS's most popular region for intensive compute will be under Titan's methane sea. High spin up cost, but cheap super-conduction environment once you're up.
I wonder when that was written...
Yes, you need equipment that can swap being hot and cold, but it's a lot easier to get to :)
It's not even the longest-lived company in the world. This construction company was founded in 578 AD and continuously operated until 2006 when it was bought by a larger company: https://en.wikipedia.org/wiki/Kong%C5%8D_Gumi
100 years ago was only 1919 -- here are some random companies from 1919 that I found on Wikipedia (ignoring for a moment that this is plainly surviorship bias):
Companies surviving for 100 years isn't quite routine but it's certainly not so rare that its surprising when one does. I don't think it's at all inconceivable that Amazon could stay open for a hundred years. It's made it past the first 10 years, the turbulent start when most companies are culled. I'd wager that the biggest threat to Amazon surviving to 100 is being broken up a la Bell/Standard Oil.
Second, that's average time in the S&P 500 index. As noted and n the report, there are many reasons besides going under that companies drop off the index. That number doesn't really say much about longevity of the company.
Bayer (1860s Germany), Johnson & Johnson (1886), 3M (1902), the Coca-Cola Company (1892), IBM (1911), HP (1939), Mitsubishi (1870), Wells Fargo (1852).
According to this (at the time of reading) a one way trip at the speed of light is ~75 minutes, so you will have approximately two and a half hours of ping.
Still, it raises an interesting question: how would a hypothetical Earth-Titan network protocol work?
Obviously latency is going to be extremely high, but I can't really understand why data rates are still so low?
That received signal strength is what determines channel capacity (C) which is the upper limit on the bit rate you can get.
see Friis and Shannon's channel capacity
Latency is high, but the power you have to pump through an antenna / laser to get enough watts on the receiver goes up really fast with distance.
Here's a summary that touches on it if you'd like to learn more: http://www.qrg.northwestern.edu/projects/vss/docs/Communicat...
And here's a detailed derivation for voyager. https://space.stackexchange.com/questions/24338/how-to-calcu...
Now figuring out which 10 seconds to select and send to earth... that'll be interesting. An on-board cache of x GB data storage, with key frames taken every 30 minutes, would probably be able to select some pretty compelling 10 second segments.
Caching everything then sending it at leisure is working nicely for New Horizons.
If clock A could reach the speed of light (which it can't), then, yes, clock B would appear to be 'frozen in time'.
> Does a photon in a vacuum arrive instantly at its destination?
From the perspective of any possible observer, no, it always appears to be traveling at the speed of light. If an observer could travel at the speed of light (which it can't), then, yes, it would appear as if it arrived instantly in the sense that clocks at both its source and destination would appear to be not running at all.
> If a photon looks at another photon, does the other photon appear not to be moving at all, or... Ouch my brain.
Yeah, this is tricky. Photons can't look or see – what could that mean as looking/seeing involves detecting photons (or, in the sense that something like echolocation is 'seeing', detecting a pattern of matter, e.g. sound)? In a sense, not moving at all or both moving at the same maximum speed don't seem to be much different, from the 'perspective' of a photon.
Somewhat related, this video describes how, if one could travel on a vehicle that could accelerate at a constant rate continuously for decades, one would eventually see the cosmic microwave background radiation as a rainbow ring because traveling closer and closer to the speed of light would shift the apparent frequency of the radiation first into the visible spectrum (and then beyond it).
>> The Pentagon is aware of a Russian test of a nuclear-powered cruise missile but the system is still under development and had crashed in the Arctic in 2017. A RAND Corporation researcher specializing in Russia said "My guess is they're not bluffing, that they've flight-tested this thing. But that's incredible."
The nuclear powered missiles use the fission reaction to heat incoming air similar to how a jet engine works.
On the other hand, a hot-air balloon kept aloft by excess heat from radioactive metal might be a more attractive option if we were selecting proposals based on awesomeness.
Unfortunately, there is a shortage of plutonium-238 to run these RTGs (see above story). I guess that will get resolved somehow.
The current Mars Curiosity rover is powered by an RTG. Since this is the first flying (post-landing of course) probe I suppose it will be the first nuclear powered flight of a planetary probe.
radio-isotope decay -> heat -> Peltier stack -> electricity.
Advantages: no moving parts, no vibration, infinitesimal mass change, exceedingly reliable. 'Small'
Disadvantage: Efficiency kinda crummy at ~5%. Slowly loses output as fuel decays and the Peltier stack degrades.
Serious question: Why is it not OK to have a standard sensor array on every planet in the solar system?
Because we don't live in a fictional sci-fi universe where launching things into space doesn't cost a ridiculous amount of money, time and effort, and can't only be done at certain times from certain locations in order to get the orbits right, or where years of effort and millions of dollars (or whatever currency) don't also go into building the things to be launched into space. The world has better things to spend its money on.
>Why is it not OK to have a standard sensor array on every planet in the solar system?
What is a "standard sensor array?" We've already sent a lot of probes to a lot of places around the solar system. But read the rest of this thread - it's a lot more complicated than it seems. Also, remember how hostile and difficult the solar system can be. Jovian planets don't even have a solid surface to be "on," for instance, and Venus has a pressure of 90 atmospheres and it rains sulfuric acid.
That's both the tech upgrade during the n-year coast phase, and the investigation upgrade as they work out new things to investigate.
It's not as straightforward as spamming the system with cameras. That's bound to happen more, after the MarCO cubesats had success flying along with Insight.
Not just a little, but a lot of water:
> The density of Titan is consistent with a body that is about 60% rock and 40% water.
> Pre-Cassini models of impact trajectories and angles suggest that where the impactor strikes the water ice crust, a small amount of ejecta remains as liquid water within the crater. It may persist as liquid for centuries or longer, sufficient for "the synthesis of simple precursor molecules to the origin of life".
That's extremely misleading.
First, rocks have different densities. Sandstone weighs 2g/cc, basalt weighs 3g/cc, so a density "consistent with" 50% basalt, 50% water would be equally consistent with 100% sandstone, not to mention the possibilities of rocks with drastically different densities such as pumice or iron.
Secondly, we are pretty certain Titan has large quantities of liquid methane and/or ethane (check the same Wikipedia link) which certainly account for some of the difference in density between Titan and other rocky bodies.
So yes, there is water on Titan, but it's about as likely to be 40% water as it is to be 40% cheese or 40% iPhones, even if its density suggests a makeup consistent with that.
You're right - I should have said: "potentially a lot of water."
Sandstone (silicon oxides) seems unlikely given the reducing nature of the atmosphere. I'm no expert, but when liquid hydrocarbons rain down, there's not a lot of free oxygen on the surface at least. Ditto for basalt, which is about 40-50% silicon oxide. Still there could have been some process by which the interior sequestered most of the planet's oxygen, leaving what remained on the surface as water.
In contrast, liquid hydrocarbons seem plausible given the stuff rains down from the atmosphere and its density (methane ~0.5 g/mL, -162 C).
Titan's orbit provides some evidence consistent with a body that's more dense at the surface than at the core. One explanation is large amounts of subsurface liquid, but there are others:
There's been some discussion about the apparent massive block of ice in Titan's surface, so the idea that Titan's putative subsurface ocean could contain water isn't too wild a speculation:
A subsurface ocean composed of water and liquid hydrocarbons would be consistent with everything I've been able to find so far.
I think this type of projects would be a great bipartisan way to unite the country, as happened during the space race in the middle of the 20th century.
It might also revive some interest in STEM.
Anyway, Dragonfly: RTG-powered quadcopter to fly around Titan's low gravity and dense atmosphere. Over its 2.5-year primary mission, Dragonfly should cover ~180 kilometers of territory.
Self-promotion: If you're into space exploration, check out
our weekly space industry newsletter called The Orbital Index (https://orbitalindex.com). We're going to cover this in depth in next week's issue.
I think NASA used to get a lot of fascination from doing the seemingly impossible like flying to the moon. So I think a mission like this will be fascinating for a lot of people. Also it may spawn off a lot of technology. I hope for a submarine mission to Europa.
Even this relatively "inefficient" quadcopter (8 rotor) design could cover dozens of miles (~60km, more than any Mars rover has ever done in its entire mission) in a single hop (which could be recharged by the MMRTG in a single week-long night), although prudence suggests shorter hops at first. That means in principle over its ~10 year lifespan (assuming it can last as long as Cassini did...) it could nearly circumnavigate the entire planet (diameter of ~5000km, day period of about 16 Earth days) while visiting dozens of sites. Granted, range will likely be much more modest as the mission operators will be focusing on not losing this valuable asset, but it shows just how powerful the ability to fly could be. It can visit more sites than all the surface robotic missions to Mars combined. In that sense, it's a fantastic scientific value. And I think the public will absolutely love it.
Information from the Dragonfly proposal document: http://dragonfly.jhuapl.edu/News-and-Resources/docs/34_03-Lo...
Cassini wasnt exposed to solvents, rocks and didn't have moving parts (at least not to keep it aloft). Have they made a public statement about lifespan?
Too bad it results in an 11 year transit time though! Flying direct would save almost 8 years of that...
Also, you're reading that delta-v map completely wrong. The red arrows mean you can aerobrake. So it only takes about 4.1km/s to reach Saturn if you start out at a highly elliptical (near escape) Earth orbit and do a large departure burn at perigee. (See here: https://en.wikipedia.org/wiki/Delta-v_budget#Interplanetary
...the 7.3km/s if the burn is done starting in LEO, minus the 3.2km/s benefit you'd get if starting near c3=0. Or you add up the numbers on your delta-v map that can't be done using aerobraking, and you get the same 4.1km/s delta-v if starting from Earth escape.)
...so a fueled up Starship could send a payload direct to Titan and still have enough propellant to propulsively brake back to Earth orbit immediately after sending the Titan payload on its way.
(But that's just one option... Lots of other vehicles could do it if you used refueling or some high performance kick stages or in orbit rendezvous.)
Maybe they could produce more fuel and oxidizer in situ, and maybe Earth is a more attractive target for aerocapture, and maybe gravity assists line up better one way or the other, but it's not a bad starting point to assume a round trip is far more expensive than a one-way trip.
I'm not sure on what basis he thinks Starship might be able to get there in the first place.
It is an interesting question for sure, especially given that one of the stated goals for Starship (IIRC) is to enable exploration of the outer planets.
Can you fit that equipment in a single Starship, by mass and volume? Is that what we're talking about here? No idea.
Why is that?
NASA's announcement video: https://youtu.be/xn3-0a19sC8
Exciting to see reality (almost) following fiction. Gattaca is an excellent film, if you haven’t seen it.
Myself, I'm absolutely fascinated by the confirmed hydrocarbon lakes and rivers on Titan and can't wait to see actual optical images from up close (so far we only got synthetic-aperture radar images ).
Also, it's interesting that since they can't study Titan very well visually (you can't point a telescope at it and map the surface like you can with Mars) they're planning on sending a rover that can cover far more distance since they have less idea what will be "interesting" beforehand.
Even then we were speculating on flying or floating probes for future missions there. At the time it was assumed that the surface could well be entirely liquid.
Relying solely on NASA and the political funding machinations of the White House and Congress would put our understanding of the planets very far behind.
APL has long bid on missions and instrument proposals just like other institutions.
NASA likely wouldnt even have revisited this moon without the European probe taking pictures under the atmosphere
It is nice that multiple public sector agencies worldwide are doing space travel now
Can we be 100% sure there isn't life.
It’s the human spaceflight program that has had the, um, difficulties. There are signs of hope, though.
Probably because the senate keeps their corrupt hands off of these types of missions.
A helicopter sounds great, but perhaps it would make sense to try to simply make a probe that can stay alive there long enough to do anything other than send a couple pictures back.
Venus, definitely. Titan though? Huygens is the only probe that's ever touched down there, and it's operational life was tied to its battery life and the fact that Cassini wouldn't be around very long to listen to it. Cassini was on a flyby trajectory, not an orbit around Titan, so as soon as the orbiter went over the horizon, that was it. Outfitting Huygens with enough power to stay on for future flybys would require MUCH more power, a job for which only an RTG would be appropriate since solar is out of the question that far out/under that atmosphere, and batteries just flat out don't last that long.
Nothing about the moon itself prevented a long operational life.
This is exactly why I like HN. Here, you have the true experts contributing valuable science with their credentials laid bare, as opposed to the pencil pushers at NASA who probably only approved this mission because it sounded cool.
Once you relax the requirement that 'answers' must be 'yes or 'no' to 'more likely' or 'less likely', it should be clearer how one would go about searching for life. For one, is there chemical activity one wouldn't otherwise expect if there was no life?