Yes! We ARE going to Europa!

[Camacha]

"WE" represents the humanity and our effort to go there via space probe.

We, humanity, and our ambassadors, the robots.

[Hcube]

We could possibly send a small nuclear reactor on Europa's surface to melt down into subsurface ocean and deploy something like a submarine to explore it. If some people weren't against nuclear stuff in space

Surely a RTG would be more than enough to melt the ice... that is nuclear and has been used a few times, people are OK with that. But i don't think it's going to happen

[Thomassino]

Surely a RTG would be more than enough to melt the ice... that is nuclear and has been used a few times, people are OK with that. But i don't think it's going to happen

At least in the near future. When you think about it, cultural and psychological effects of possible discovery of extraterrestrial life would be staggering.

[Mitchz95]

Question: would the heat of an RTG be enough to sterilize it? We wouldn't want to contaminate any lifeforms we encounter on Europa.

[Thomassino]

Question: would the heat of an RTG be enough to sterilize it? We wouldn't want to contaminate any lifeforms we encounter on Europa.

That RTG would have to be sterilized as hell but you really can't be 100% sure if something haven't survived. I mean, recently have been discovered bacteria that are immune to NASA's sterilization systems, so we could easily have contaminated for example Mars.

[andrewas]

Surely a RTG would be more than enough to melt the ice... that is nuclear and has been used a few times, people are OK with that. But i don't think it's going to happen

Its going to take a lot of power. The probe is going to have to melt its way through 10 to 30 kilometers of ice at very low temperatures, unspooling a cable as it goes. The 30Km of cable alone mean the probe is going to have to be huge, never mind the multiple exploration craft that should be carried to maximize the science return. An RTG putting out a kilowatt or two isn't going to cut it. Its going to take a fission reactor or other equally high density power source.

[Thomassino]

Its going to take a lot of power. The probe is going to have to melt its way through 10 to 30 kilometers of ice at very low temperatures, unspooling a cable as it goes. The 30Km of cable alone mean the probe is going to have to be huge, never mind the multiple exploration craft that should be carried to maximize the science return. An RTG putting out a kilowatt or two isn't going to cut it. Its going to take a fission reactor or other equally high density power source.

And why would you need a cable? The whole craft can melt down into ocean using gravity. Surely, it would need a lot of time.

[vger]

Dive into an open fissure?

[Kryten]

And why would you need a cable? The whole craft can melt down into ocean using gravity. Surely, it would need a lot of time.

Because an interplanetary probe you can't communicate with is not much good.

[SargeRho]

A cable would be torn apart if there's any movement of the ice sheet though. Wouldn't it be better if the craft stuck to the underside of the ice sheet, and communicated with the lander using sound?

[vger]

Because an interplanetary probe you can't communicate with is not much good.

Huh. Nothing about using a cable seems very practical though. A 30km cable... how the heck much would that weigh? And yeah you could try making it paper thin, but you're also going to want it to have a lot of durability, because a lot could happen with that much ice. One minor quake and *snap*

No alternative solutions to communicating with the surface?

[SargeRho]

I tried finding something about the propagation of sound or seismic waves through water ice, but I can't seem to find anything. Melting a microphone and speaker into the ice, as well as leaving one in the melt-torpedo would be a viable alternative is sound travels well enough through ice.

The Europa Flyby Mission also has the REASON instrument, which is an ice penetrating radar. The tech of that should be able to transmit data through the ice too.

Edited August 2, 2015 by SargeRho

[Exoscientist]

Perhaps someone could do a Kerbal simulation of this: after a Hohmann trajectory flight to the Jovian system, a spacecraft can be put in an elliptical orbit around Jupiter at Europa's distance for less than 700 m/s delta-v. To limit the total delta-v required, we want the spacecraft to be gravitationally captured by Europa. Assuming we arrange the elliptical orbit around Jupiter to come very close to Europa, how long would it take for it to be captured by Europa?

Bob Clark

[fredinno]

I did a bit of googling; I think you're right.

Here're the current figures for the Europa Clipper (although they're very likely to change). The total (wet) mass at launch is 3,582 kg (first link). The launch C₃'s, for the slow, gravity-assist Atlas V option, and the fast, direct SLS option, are 15 km²/s² and 82 km²/s² resp. (second link).

https://solarsystem.nasa.gov/europa/docs/Europa%20Clipper%20Info%20Sheet%2020130903.pdf

http://www.lpi.usra.edu/opag/jul2013/presentations/Clipper_Summary.pdf

https://i.imgur.com/NLDBExU.png

Here's the C₃ curve for the Falcon 9 (I think this is v1.0? Not sure). Either way it's probably a non-starter; even the payload to C₃=0 (i.e. earth escape) is much less than the Clipper's mass.

https://i.imgur.com/cZgr2gj.png

http://www.spaceflightnow.com/falcon9/001/f9guide.pdf

What about Falcon Heavy? Well, it seems the specs haven't been published yet, so I did some extrapolating from some information that's already public. I used the marketing specs for the Falcon Heavy -- 21.2 tons to GTO, 13.2 tons to Mars Transfer. And I used specs from the Falcon 9 v1.1 upper stage, which I understand will be used unmodified (?) on the Falcon Heavy. (If there's a secret new stage under development, then this analysis is bunk). I used the vacuum I_sp and wet/dry masses for this upper stage.

http://www.spacex.com/falcon-heavy

http://www.spaceflight101.com/falcon-9-v11.html

Here's my extrapolation. Since the booster stages cut off well before GTO velocity, I'm assuming a fit of the rocket equation, to the GTO and Mars payloads, will roughly extrapolate the payload to higher C₃'s. There's tons of implicit assumptions here, too many to even discuss. This is a messy guesstimate at best.

I did a nonlinear fit in Mathematica, using these values:

[TABLE=width: 500]

[TR]

[TD]I_sp[/TD]

[TD]340 s[/TD]

[/TR]

[TR]

[TD]F9-H stage mass, dry[/TD]

[TD]3,900 kg[/TD]

[/TR]

[TR]

[TD]F9-H propellant mass[/TD]

[TD]92,670 kg[/TD]

[/TR]

[TR]

[TD]delta-v from LEO to GTO[/TD]

[TD]2.5 km/s[/TD]

[/TR]

[TR]

[TD]C₃ to Mars transfer[/TD]

[TD]10 km²/s²[/TD]

[/TR]

[TR]

[TD]F9-H payload to GTO[/TD]

[TD]21,200 kg[/TD]

[/TR]

[TR]

[TD]F9-H payload to Mars transfer[/TD]

[TD]13,200 kg[/TD]

[/TR]

[TR]

[TD]Effective perigee altitude for Oberth (guess)[/TD]

[TD]100 km?[/TD]

[/TR]

[/TABLE]

https://i.imgur.com/6o2mtaY.png

My estimate for F9-H's payload, for the SLS-direct trajectory, is 2,664 kg. This isn't very accurate at all, but it's much less than the Clipper mass (3,582 kg), so I think the conclusion is robust: F9-H can't do the direct Jupiter trajectory, with its current upper stage.

The VEEGA trajectory is easily an option. F9-H's payload would be slightly less than the Mars transfer -- 11,549 kg for C₃=15 km²/s².

update: On the other hand, a single Star-63F upper stage -- one of the larger solid rockets of the Payload Assist Module -- placed on top of the F9-H, could comfortably launch the Clipper on a Jupiter-direct trajectory. Take the Clipper mass (3,582 kg), add 10% margin (3,940 kg). Add on a 4,590 kg Star-63 F (total 8,530 kg). From my extrapolation, the F9-H could lift this much mass to C₃ = 30.2 km²/s². (This is a more comfortable estimate: it's very close to the Mars transfer that we have a datapoint for). Then the Star-63F can give us another 2,019 km/s boost, to a final C₃ of 84 km²/s².

I think that would be credible!

Star-63F specs:

[TABLE=width: 500]

[TR]

[TD]Isp[/TD]

[TD]297 s[/TD]

[/TR]

[TR]

[TD]empty mass[/TD]

[TD]326 kg[/TD]

[/TR]

[TR]

[TD]gross mass[/TD]

[TD]4,590 kg[/TD]

[/TR]

[/TABLE]

http://www.astronautix.com/engines/star63f.htm

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

I decided to confirm this with my own calculations (using the rocket equation): http://imgbox.com/D1TZ1fqR and http://imgbox.com/Dvt4NV1Z

I found that while lower margins are possible to launch Europa Clipper to Jupiter transfer (4% with STAR-48) Falcon Heavy can not launch Europa Clipper without a reduction in payload margin, and it would be a better bet, payload-wise, to launch to Europa using the SLS. It would help fill up the launch calender anyways, and is more logical than the Voyager Mars project.

In summary, using my own calculations, I disagree with Cryogen's statement the FH can launch Europa Clipper without weight reductions or decrease in payload margin.

- - - Updated - - -

Perhaps someone could do a Kerbal simulation of this: after a Hohmann trajectory flight to the Jovian system, a spacecraft can be put in an elliptical orbit around Jupiter at Europa's distance for less than 700 m/s delta-v. To limit the total delta-v required, we want the spacecraft to be gravitationally captured by Europa. Assuming we arrange the elliptical orbit around Jupiter to come very close to Europa, how long would it take for it to be captured by Europa?

Bob Clark

Being captured by Europa is a bad thing anyways- the entire point of multiple flybys is to reduce radiation exposure from Jupiter's radiation belts.

[Exoscientist]

A cable would be torn apart if there's any movement of the ice sheet though. Wouldn't it be better if the craft stuck to the underside of the ice sheet, and communicated with the lander using sound?

Interesting idea. I wonder how much power would be needed to extend through say 5 km to 10 km of ice.

Bob Clark