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NASA plans to launch a spacecraft to Titan

theatlantic.com

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Re: NASA plans to launch a spacecraft to Titan

#61

Post by EForEndeavour »

mdorazio wrote: post #49
rzimmerman wrote: post #4

A flying drone is a really solid idea for a Titan lander for a couple reasons: * 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…

I kind of wish it had an airship counterpart. Inflating a dirigible there would take advantage of the same atmosphere + gravity benefits with the added bonus of not needing constant power to move around.

Good point: I seriously wonder if they considered a dirigible design. Buoyancy + directional propulsion does seem simpler in my space-novice opinion compared to a quadcopter. A blimp would be slower than a quadcopter, but nobody's going to be piloting the thing in real time, so that shouldn't matter.

Re: NASA plans to launch a spacecraft to Titan

#62

Post by Sharlin »

nickserv wrote: post #47
sandworm101 wrote: post #33

Earlier quoted context omitted.

No. >> 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.[17][18][19] 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." https://en.wikipedia.org/wiki/Nuclear-powered_aircraft#Russi... https://en.wikipedia.org…

This case is different though, using the fission reaction to generate electricity which in turn powers the electric motors among other things. The nuclear powered missiles use the fission reaction to heat incoming air similar to how a jet engine works.

No fission reaction, just radioactive decay in Dragonfly's case. It will use an RTG (radioisotope thermoelectric generator) not unlike Curiosity and most missions to the outer planets to date.

Re: NASA plans to launch a spacecraft to Titan

#63

Post by T-hawk »

jvanderbot wrote: post #7
rzimmerman wrote: post #4

A flying drone is a really solid idea for a Titan lander for a couple reasons: * 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…

The data rate from the surface of titan is abysmal. Even with a relay, we won't get much video, but man, I hope we get some.

From a scientific standpoint, there's really no value in downlinking video as opposed to still images. It costs several multiples worth of scarce downlink bandwidth, for a tiny gain in what there is to see of the same rocks at slightly different angles. Same reason we didn't have New Horizons at Pluto or the various Mars rovers do any video.

Re: NASA plans to launch a spacecraft to Titan

#64

Post by eindiran »

magnamerc wrote: post #44
cwkoss wrote: post #17

Earlier quoted context omitted.

In addition to lack of solar energy, I wonder if nuclear power source is necessary to keep batteries or other electronics warm enough to function properly. 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,…

I find it kind of funny that you think AWS will still be around in a hundred years.

This paper company was founded 771 AD: https://www.shinise.ne.jp/j_kyoto/voices/vol/48/48-d.html

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):

https://en.wikipedia.org/wiki/Champion_(sportswear)

https://en.wikipedia.org/wiki/KitchenAid

https://en.wikipedia.org/wiki/Thrifty_PayLess

https://en.wikipedia.org/wiki/Tesco

https://en.wikipedia.org/wiki/Proffitt%27s

https://en.wikipedia.org/wiki/Bentley

https://en.wikipedia.org/wiki/A%26W_Restaurants

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.

Re: NASA plans to launch a spacecraft to Titan

#65

Post by EForEndeavour »

whatshisface wrote: post #55
sandworm101 wrote: post #33

Earlier quoted context omitted.

No. >> 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.[17][18][19] 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." https://en.wikipedia.org/wiki/Nuclear-powered_aircraft#Russi... https://en.wikipedia.org…

Why bother? Rocket fuel is cheaper than nuclear fuel and rocket missiles can already hit anywhere.

Because a nuclear-powered missile can in principle fly in circles at low altitude off your enemy's shores for months at a time without landing or refueling, ready to be called down at any time with no detectable warning.

Re: NASA plans to launch a spacecraft to Titan

#66

Post by Robotbeat »

dflock wrote: post #45
QuotedForTruth wrote: post #19

Earlier quoted context omitted.

Even spaceX's starship/BFR with LEO refuel wouldn't work?

The delta-v required for a trip to Titan, according to this[1], is 28.43 km/s. Optimistically, a fully re-fuelled startship in LEO has ~10km/s of delta-v to spend, afaik. [1]( https://www.reddit.com/r/space/comments/1ktjfi/deltav_map_of... )

Starship can do better than that if stripped down to expendable use. About 13km/s: https://twitter.com/elonmusk/status/1111798912141017089

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.)

Re: NASA plans to launch a spacecraft to Titan

#67

Post by plutonorm »

What. How are they going to detect life on titan? They can't even detect life on mars. I mean to say, even when we know the kind of life we are looking for we get confused about how to confirm or deny its existence. So they want to design a small flying drone that works in extremely hostile conditions, that also has the kinds of sophisticated instruments needed to look for life? And not just life, life of potentially a completely unknown form, given the widely different surface conditions. This just seems like a weird mission. Finish up the Viking labelled release experiments on mars first, then go take a look in the mid Venusian atmosphere. Then take a gander at europa.... Weird mission

Re: NASA plans to launch a spacecraft to Titan

#68

Post by jvanderbot »

EForEndeavour wrote: post #61
mdorazio wrote: post #49

Earlier quoted context omitted.

I kind of wish it had an airship counterpart. Inflating a dirigible there would take advantage of the same atmosphere + gravity benefits with the added bonus of not needing constant power to move around.

Good point: I seriously wonder if they considered a dirigible design. Buoyancy + directional propulsion does seem simpler in my space-novice opinion compared to a quadcopter. A blimp would be slower than a quadcopter, but nobody's going to be piloting the thing in real time, so that shouldn't matter.

Yes, that was a mission proposal years ago, a blimp and quads. It was not selected then or rehashed this time. In addition, a blimp only concept has been floated (ha!) as well.

Re: NASA plans to launch a spacecraft to Titan

#69

Post by EForEndeavour »

sandworm101 wrote: post #33
p1mrx wrote: post #28

Earlier quoted context omitted.

Will this be the first-ever instance of nuclear-powered flight?

No. >> 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.[17][18][19] 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." https://en.wikipedia.org/wiki/Nuclear-powered_aircraft#Russi... https://en.wikipedia.org…

I hadn't heard of the 9M730. That page links to one for the US Air Force's Supersonic Low Altitude Missile (SLAM) or "flying crowbar" of the 50s and 60s, which makes for fascinating reading: https://en.wikipedia.org/wiki/Supersonic_Low_Altitude_Missil...

Re: NASA plans to launch a spacecraft to Titan

#70

Post by jvanderbot »

nsxwolf wrote: post #58
rzimmerman wrote: post #4

A flying drone is a really solid idea for a Titan lander for a couple reasons: * 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…

What about hydrogen fuel cells? Isn't the whole place basically nothing but fuel?

Those work by combining H with O. Not much available oxygen there.
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