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Pluto/Triton Lander Deceleration, using thin atmospheres for EDL
stevesliva
post Jul 6 2015, 06:17 PM
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QUOTE (gallen_53 @ Jul 5 2015, 12:35 AM) *
I still think MSL was a mistake because the money spent on it would have been better spent mass-producing MER clones but that's another story.


There's discussion here about that. Probably a lot, that the moderators may well have excised from other threads and created new ones for.... In any event, one of the bigger issues is the MER sites had to be fairly close to the equator. The airbag EDL stuff had hit a dead end, not only for size.
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stevesliva
post Jul 6 2015, 06:20 PM
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QUOTE (gallen_53 @ Jul 5 2015, 04:26 AM) *
If I was king, I'd send a flagship class spacecraft to Saturn. While entering the Saturn system, I'd drop a lander on Titan that could float on one of Titan's ethane lakes, split off a separate lander to Phoebe, do the Saturn orbit insertion burn and then send the main spacecraft to Enceladus to look for sea monsters.


Makes me think of Cassini. The King is dead! Long live the King!
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djellison
post Jul 6 2015, 06:51 PM
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QUOTE (gallen_53 @ Jul 5 2015, 12:26 AM) *
the Dawn spacecraft is very exciting because it has fully demonstrated the capability of solar electric propulsion


This was done 15 years before by Deep Space 1.
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JTN
post Jul 6 2015, 09:37 PM
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The caption of one of the images in this article suggests there may have been at least one more study of a Pluto lander (unless it refers to one of the ones already mentioned? Or maybe never more than a wild idea? I've done 0 research).
QUOTE
Planetary scientists were desperate to make a Pluto flyby affordable enough to become a reality in the early 1990s. In 1994, they began talks with the Russians to add a Soviet Zond probe to the NASA spacecraft.

I'm surprised that these feeble atmospheres are substantial enough to even be considered to slow down a lander. Do they suffer from the Mars problem, of being too thin to slow you down but thick enough that you can't just ignore them?
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Aldebaran
post Jul 15 2015, 07:25 AM
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Now we need to develop propulsion systems that use practically no propellant. Only recently, the idea was regarded as controversial, but the RF resonant cavity thruster is starting to look promising. (or at least not impossible)
http://ntrs.nasa.gov/search.jsp?R=20140006052
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Juramike
post Jul 15 2015, 02:06 PM
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While a new thruster technology would be a welcome addition to the collective toolkit, for the purposes of this discussion we should limit it to proven and near-term available thrusters and technologies.


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Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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Aldebaran
post Jul 16 2015, 10:17 AM
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QUOTE (Juramike @ Jul 15 2015, 03:06 PM) *
While a new thruster technology would be a welcome addition to the collective toolkit, for the purposes of this discussion we should limit it to proven and near-term available thrusters and technologies.


Fair enough, but it could turn out to be a huge game changer. I'll leave it at that.
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Y Bar Ranch
post Jul 16 2015, 02:50 PM
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QUOTE (Juramike @ Jul 15 2015, 09:06 AM) *
While a new thruster technology would be a welcome addition to the collective toolkit, for the purposes of this discussion we should limit it to proven and near-term available thrusters and technologies.

Does one exist in the current stable of solutions?

A place like Pluto probably (I am guessing) has an atmosphere so thin and an approach velocity so high, that there wouldn't be enough pure aerobraking available to enter into orbit, much less land without making a crater.

My thought is an aerodynamic lifting shape that will enter the atmosphere and then use lift to stay in the atmosphere, bending around the planet with the lift vector pointing down to augment gravity, until it has bled off its speed and is below escape velocity, at which time you could pop up into orbit and get down to the surface from there.

It would put Star Wars canyon to shame, flying just off the surface "upside-down". smile.gif
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djellison
post Jul 16 2015, 03:08 PM
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To drop from 14km/sec to 1.2km/sec ( which is what you basically have to do ) in, say, an 1800km quarter circumference of Pluto would require an average deceleration of 5G. In your example - you would have to generate even more acceleration than that! It's just not going to happen.
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Y Bar Ranch
post Jul 16 2015, 04:14 PM
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QUOTE (djellison @ Jul 16 2015, 11:08 AM) *
To drop from 14km/sec to 1.2km/sec ( which is what you basically have to do ) in, say, an 1800km quarter circumference of Pluto would require an average deceleration of 5G. In your example - you would have to generate even more acceleration than that! It's just not going to happen.

Whippin' out my Casio...based on the Pluto radius and a 14 km/s approach speed, you'd have to pull 17 Gs at the maximum to stay in the atmosphere. With a swag on density rho of 2 x 10^-5 kg/m^3, and a mass of entry probe of 1 KG and C_L_max of 1.5, you'd need a....really, really big wing. huh.gif
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