So here's my idea for a Sedna mission... HEAR ME OUT ON THIS

[_Augustus_]

WISPIE (Wide-Intercept Sedna Perihelion Interstellar Explorer) is my work-in-progress proposal for a Sedna flyby launched on the SLS Block II in early 2028 or 2030.

The probe would be slightly smaller than New Horizons, and be powered by 2 MMRTGs or maybe Am-241 RTGs. Budget cap is 2 billion in 2015 US dollars.

Upper mass limit is 600 kg, and the probe would more likely be about the size of Pioneer 10 or 11.

I am going to actually write a paper on it as a candidate for a Flagship mission, but that's beside the point.

Anyway, my questions are:

1. Would it be easy enough to fly by Quaoar (I checked and it is in a good spot to do this) and then do a cheap course correction to get to Sedna?

2. Could anyone make artwork for this thing?

3. What is the maximum payload limit to Sedna assuming the use of a sunshield and the Oberth effect?

4. Is the SLS (105-130t to LEO) necessarily needed for this mission? What about the Falcon Heavy (70t to LEO) or MCT rocket (~140t to LEO)

Thanks, post thoughts!

Edited November 8, 2015 by _Augustus_

[Sylandro]

Sounds interesting!

[fredinno]

WISPIE (Wide-Intercept Sedna Perihelion Interstellar Explorer) is my work-in-progress proposal for a Sedna flyby launched on the SLS Block II in early 2028 or 2030.

The probe would be the size of New Horizons or smaller, and be powered by an MMRTG.

I am going to actually write a paper on it as a candidate for a Flagship mission, but that's beside the point.

Anyway, my questions are:

1. Is sacrificing payload mass worth the years of time saved by doing an Oberth maneuver close to the Sun (By adding a MESSENGER-style sun shield that detaches once away from the Sun) instead of a Jupiter assist?

2. If using a Jupiter assist in 2028 or 2030, would it be easy enough to fly by Quaoar (I checked and it is in a good spot to do this) and then do a course correction to get to Sedna?

3. Could anyone make artwork for this thing?

Thanks, post thoughts!

I would recommend a backup version using SLS Block IB in case SLS Block II is not built (somewhat likely, as it's not really needed for any near-term SLS missions.)

[_Augustus_]

I would recommend a backup version using SLS Block IB in case SLS Block II is not built (somewhat likely, as it's not really needed for any near-term SLS missions.)

But Block II's boosters are needed eventually, as they only have so many Shuttle ones.

[Armchair Rocket Scientist]

1. Is sacrificing payload mass worth the years of time saved by doing an Oberth maneuver close to the Sun (By adding a MESSENGER-style sun shield that detaches once away from the Sun) instead of a Jupiter assist?

Depends on how much payload and how much time. A major constraint on a mission like this is that the power output of RTGs gradually declines: making a probe that gets to Sedna 50 years after launch isn't necessarily that useful.

2. If using a Jupiter assist in 2028 or 2030, would it be easy enough to fly by Quaoar (I checked and it is in a good spot to do this) and then do a course correction to get to Sedna?

How big is your course correction? Your probe is going to be going FAST when it flies by Quaoar if you want to reach Sedna in a reasonable timeframe. Even a tiny change in direction could end up costing multiple km/s of dV (which is a big deal for a small probe).

Now, I have a question of my own:

Why Sedna? We've already done a flyby of Pluto, so we have a decent idea of what TransNeptunian objects look like. Yes, Sedna's weird orbit raises a lot of questions, but how many of those could be answered by a flyby lasting just a few hours?

And there are many other promising targets for flagship missions, including long-duration exploration of Europa, Titan, Enceladus, Uranus, or Neptune.

If you want to make a serious mission proposal, you need to do two things: first, show that it is technically feasible, and second, justify spending money on your mission instead of the other mission proposals competing for the same funding.

[fredinno]

But Block II's boosters are needed eventually, as they only have so many Shuttle ones.

If Block II is not made, they will use smaller Dark Knight SRBs.

- - - Updated - - -

Depends on how much payload and how much time. A major constraint on a mission like this is that the power output of RTGs gradually declines: making a probe that gets to Sedna 50 years after launch isn't necessarily that useful.

How big is your course correction? Your probe is going to be going FAST when it flies by Quaoar if you want to reach Sedna in a reasonable timeframe. Even a tiny change in direction could end up costing multiple km/s of dV (which is a big deal for a small probe).

Now, I have a question of my own:

Why Sedna? We've already done a flyby of Pluto, so we have a decent idea of what TransNeptunian objects look like. Yes, Sedna's weird orbit raises a lot of questions, but how many of those could be answered by a flyby lasting just a few hours?

And there are many other promising targets for flagship missions, including long-duration exploration of Europa, Titan, Enceladus, Uranus, or Neptune.

If you want to make a serious mission proposal, you need to do two things: first, show that it is technically feasible, and second, justify spending money on your mission instead of the other mission proposals competing for the same funding.

Sedna is a potential Oort Cloud Object, a category of objects we know nothing about. The possinble future discovery of why it has a strange orbit is just the iciing on the cake.

I think it was more supposed to be a "Better, Faster Cheaper" kind of mission, using New Horisons, which was a New Frontiers Mission, as a basis. Maybe the cost for the mission would not be flagship, due to the smaller size, and the use of existing hardware, but I guess the use of SLS bumps it up to a flagship mission regardless....

[More Boosters]

If Block II is not made, they will use smaller Dark Knight SRBs.

- - - Updated - - -

Sedna is a potential Oort Cloud Object, a category of objects we know nothing about. The possinble future discovery of why it has a strange orbit is just the iciing on the cake.

I think it was more supposed to be a "Better, Faster Cheaper" kind of mission, using New Horisons, which was a New Frontiers Mission, as a basis. Maybe the cost for the mission would not be flagship, due to the smaller size, and the use of existing hardware, but I guess the use of SLS bumps it up to a flagship mission regardless....

Dark Knight is just one of the three possible boosters for Block II though.

[MichaelPoole]

I wholly support this.

Also, Sedna is a lot colder than Pluto and can harbor exotic ices that are gaseous at Pluto temperatures. I honestly very much dislike the "you've seen one you've seen them all" fallacy. Everyone expected Pluto to be either exactly the same as Triton or a cratered dead iceball yet it turned out to be neither of that. Moons of giant planets are all very much different in their geological history and composition and yet they are all similiar sized when it comes to moons for each planet with a few outliers and orbit the same distance from the Sun. The Jupiter system contains both the most active and the least active major solar system body (Io vs Callisto). You might say "but tidal heating..." except none of the moons of Uranus get any appreciable tidal heating at the moment, yet Miranda is a crazy world of chasms and 25 km high cliffs, Ariel has frozen "rivers" of ancient half-melted ice "lava" flows, Titania has a thin CO2 atmosphere and is criss-crossed with chasms, Umbriel is a crater ball - except fully black, yet one crater is bizzarely white, Oberon is a reddish cratered world. Look at Pluto and Charon - drastically different worlds. Sedna is Charon sized, but much colder. At aphelion, it is cold enough to freeze hydrogen. Right now, it might be warm enough for a nitrogen atmosphere. The temperature difference between perihelion and aphelion of Sedna are quite major. Think Pluto has dramatic seasons? Sedna is FAR more extreme.

[giatthampro]

Thank for this content

[Scotius]

I wholly support this.

Also, Sedna is a lot colder than Pluto and can harbor exotic ices that are gaseous at Pluto temperatures. I honestly very much dislike the "you've seen one you've seen them all" fallacy. Everyone expected Pluto to be either exactly the same as Triton or a cratered dead iceball yet it turned out to be neither of that. Moons of giant planets are all very much different in their geological history and composition and yet they are all similiar sized when it comes to moons for each planet with a few outliers and orbit the same distance from the Sun. The Jupiter system contains both the most active and the least active major solar system body (Io vs Callisto). You might say "but tidal heating..." except none of the moons of Uranus get any appreciable tidal heating at the moment, yet Miranda is a crazy world of chasms and 25 km high cliffs, Ariel has frozen "rivers" of ancient half-melted ice "lava" flows, Titania has a thin CO2 atmosphere and is criss-crossed with chasms, Umbriel is a crater ball - except fully black, yet one crater is bizzarely white, Oberon is a reddish cratered world. Look at Pluto and Charon - drastically different worlds. Sedna is Charon sized, but much colder. At aphelion, it is cold enough to freeze hydrogen. Right now, it might be warm enough for a nitrogen atmosphere. The temperature difference between perihelion and aphelion of Sedna are quite major. Think Pluto has dramatic seasons? Sedna is FAR more extreme.

Very good point. But therein lies the problem: too many fascinating places to visit, only so much money to spend.

[PB666]

WISPIE (Wide-Intercept Sedna Perihelion Interstellar Explorer) is my work-in-progress proposal for a Sedna flyby launched on the SLS Block II in early 2028 or 2030.

The probe would be the size of New Horizons or smaller, and be powered by an MMRTG.

I am going to actually write a paper on it as a candidate for a Flagship mission, but that's beside the point.

Anyway, my questions are:

1. Is sacrificing payload mass worth the years of time saved by doing an Oberth maneuver close to the Sun (By adding a MESSENGER-style sun shield that detaches once away from the Sun) instead of a Jupiter assist?

2. If using a Jupiter assist in 2028 or 2030, would it be easy enough to fly by Quaoar (I checked and it is in a good spot to do this) and then do a course correction to get to Sedna?

3. Could anyone make artwork for this thing?

Thanks, post thoughts!

If you are doing a mercury flyby why not add a load of xenon put some of these newfangled hall effect thruster on it and when you get to mars orbit detach the shield.

[Streetwind]

You probably know full well that this is a topic close to my heart

But your proposal, from what I see, doesn't solve a critical issue with this kind of mission: communications power. A MMRTG isn't going to cut it.

For starters, you're going to be flying a long time. 20 to 30 years perhaps. Plutonium is going to decay and you're going to lose power. And what's more: the thermocouples that create the electricity decay too, and they decay faster than the plutonium. While the half-life of the radioactive elements may be over 80 years, chances are you'll drop to 50% output in 40 years already. (I guess you could check how Voyager is doing for power nowadays to get a more accurate number.)

And then there's pure distance. Consider New Horizons, which also carries a RTG - one that was 10 years old at the time of the flyby, not 20 or 30. Also, that's not a MMRTG rated at 110 W nominal power, but rather a larger one rated at 250 W. By the time it arrived at Pluto, it was down to 200 W. And the New Horizons team will be waiting for over sixteen months in total just to download all the data they have collected. The reason for that? Distance, and power. The RTG is so weak, it can barely maintain 1 kBit (not byte, bit) worth of transfer rate, even with an antenna the size of the whole spacecraft. During an AMA preceding the flyby event, the New Horizons team even stated that they intentionally didn't mount bigger telescopes and higher resolution instruments because it was already a pain in the rear to transmit data as is.

Sedna is twice that distance away, and the MMRTG will be putting out a lot less power once you get there. You'll have maybe 70 W left. How are you supposed to get any data back at all? Your signal might start to get lost in background noise by that point, and even if it doesn't, you'll need absurd amounts of expensive DSN time to download even one compressed image.

I really think that if we were to start a Sedna mission, we would need to give it more than just a couple watts worth of power, if only to drive the antenna. Give it half a kilowatt instead of 0.07 kW, then we might be talking! Of course, to achieve that, you'd have to provide 0.8 to 0.9 kW at launch. That's comparable to what Cassini-Huygens has onboard. It launched with about 33 kg of plutonium, as opposed to the 4 kg that the MMRTG on Curiosity has. Can your mission proposal deal with purchasing eight times the amount of plutonium? And your spacecraft with four times as much weight dedicated to power generation? Keep in mind that the US may not even have that amount of plutonium in stock, even if you had all the money in the world. You'd have to pay to restart production.

Of course, it might be worth considering to restart the cancelled ASRG program, which aimed to produce a much higher efficiency generator weighing 25% less than a MMRTG, carrying only a quarter the plutonium, yet still producing 140 W as opposed to 110 W. With six of those things, you could get 840 W power output with just 1/6th the plutonium, with just a slightly worse total weight. And that's assuming you can't scale the unit up for significantly improved power/weight, as RTGs usually do when scaled up. Of course, there's downsides to this too: you'd have to restart and finish the cancelled development program, as mentioned before. And, can you guarantee that the stirling pistons used in these units can survive 20-30 years in deep space without breaking?

So yeah... this is not going to work with an MMRTG. You need much, much more power.

Also, patience may be a virtue here. As much as I want to learn more about Sedna, we can still intercept it at perihelion if we launch around 2050 instead of 2030. Just imagine what kind of technology we might be able to throw at the problem then!

Edited November 7, 2015 by Streetwind

[_Augustus_]

Depends on how much payload and how much time. A major constraint on a mission like this is that the power output of RTGs gradually declines: making a probe that gets to Sedna 50 years after launch isn't necessarily that useful.

How big is your course correction? Your probe is going to be going FAST when it flies by Quaoar if you want to reach Sedna in a reasonable timeframe. Even a tiny change in direction could end up costing multiple km/s of dV (which is a big deal for a small probe).

Now, I have a question of my own:

Why Sedna? We've already done a flyby of Pluto, so we have a decent idea of what TransNeptunian objects look like. Yes, Sedna's weird orbit raises a lot of questions, but how many of those could be answered by a flyby lasting just a few hours?

And there are many other promising targets for flagship missions, including long-duration exploration of Europa, Titan, Enceladus, Uranus, or Neptune.

If you want to make a serious mission proposal, you need to do two things: first, show that it is technically feasible, and second, justify spending money on your mission instead of the other mission proposals competing for the same funding.

I don't know if the course correction would need to be that big, as Quaoar itself is big enough to be used for a slight plane change. Both Sedna and Quaoar are fascinating objects (Quaoar is really just icing on the cake), with Sedna being a possible Hills Cloud object or captured rogue dwarf planet.

Furthermore Sedna has odd rotation but no moons, and it could prove or disprove a Trans-Neptunian planet.

Your point about the RTG is excellent, along with the fact that we want mission engineers and the president that orders it's construction to be still alive when it arrives.

And I'll be writing a whole paper on this. Promise.

If Block II is not made, they will use smaller Dark Knight SRBs.

- - - Updated - - -

Sedna is a potential Oort Cloud Object, a category of objects we know nothing about. The possinble future discovery of why it has a strange orbit is just the iciing on the cake.

I think it was more supposed to be a "Better, Faster Cheaper" kind of mission, using New Horisons, which was a New Frontiers Mission, as a basis. Maybe the cost for the mission would not be flagship, due to the smaller size, and the use of existing hardware, but I guess the use of SLS bumps it up to a flagship mission regardless....

The Uranus orbiter that is currently the top priority after Europa Clipper has actually begun construction would be a New-Horizons-sized probe that orbits Uranus, and it would be launched on the SLS Block IB or II and be a New Frontiers mission.

Dark Knight is just one of the three possible boosters for Block II though.

There's only 2 boosters left - Dark Knight and that other one. Pyrios is being considered for a future evolved SLS that also uses the J2X though.

Regardless, they will still be making the SLS carry 130t to LEO.

I wholly support this.

Also, Sedna is a lot colder than Pluto and can harbor exotic ices that are gaseous at Pluto temperatures. I honestly very much dislike the "you've seen one you've seen them all" fallacy. Everyone expected Pluto to be either exactly the same as Triton or a cratered dead iceball yet it turned out to be neither of that. Moons of giant planets are all very much different in their geological history and composition and yet they are all similiar sized when it comes to moons for each planet with a few outliers and orbit the same distance from the Sun. The Jupiter system contains both the most active and the least active major solar system body (Io vs Callisto). You might say "but tidal heating..." except none of the moons of Uranus get any appreciable tidal heating at the moment, yet Miranda is a crazy world of chasms and 25 km high cliffs, Ariel has frozen "rivers" of ancient half-melted ice "lava" flows, Titania has a thin CO2 atmosphere and is criss-crossed with chasms, Umbriel is a crater ball - except fully black, yet one crater is bizzarely white, Oberon is a reddish cratered world. Look at Pluto and Charon - drastically different worlds. Sedna is Charon sized, but much colder. At aphelion, it is cold enough to freeze hydrogen. Right now, it might be warm enough for a nitrogen atmosphere. The temperature difference between perihelion and aphelion of Sedna are quite major. Think Pluto has dramatic seasons? Sedna is FAR more extreme.

Thank you! I might put some of your info in the paper.

Thank for this content

You're welcome.

Very good point. But therein lies the problem: too many fascinating places to visit, only so much money to spend.

Not true. SLS Block II will cost about $600 million to build and launch, and WISPIE will be smaller than New Horizons due to shorter flyby time and constraints on payload mass and electricity usage as we need to fit in a starshield and the thing will only use 1 MMRTG, which provides roughly half the power as NH's RTG. This means that the total cost of the probe to build, launch, and fly it should be less than 1.5 billion, which is about the same price as Europa Clipper or M2020.

WISPIE, Europa Clipper and M2020 are quasi-flagship missions, really. A true flagship mission can cost as much as 3 billion.

- - - Updated - - -

You probably know full well that this is a topic close to my heart

But your proposal, from what I see, doesn't solve a critical issue with this kind of mission: communications power. A MMRTG isn't going to cut it.

For starters, you're going to be flying a long time. 20 to 30 years perhaps. Plutonium is going to decay and you're going to lose power. And what's more: the thermocouples that create the electricity decay too, and they decay faster than the plutonium. While the half-life of the radioactive elements may be over 80 years, chances are you'll drop to 50% output in 40 years already. (I guess you could check how Voyager is doing for power nowadays to get a more accurate number.)

And then there's pure distance. Consider New Horizons, which also carries a RTG - one that was 10 years old at the time of the flyby, not 20 or 30. Also, that's not a MMRTG rated at 110 W nominal power, but rather a larger one rated at 250 W. By the time it arrived at Pluto, it was down to 200 W. And the New Horizons team will be waiting for over sixteen months in total just to download all the data they have collected. The reason for that? Distance, and power. The RTG is so weak, it can barely maintain 1 kBit (not byte, bit) worth of transfer rate, even with an antenna the size of the whole spacecraft. During an AMA preceding the flyby event, the New Horizons team even stated that they intentionally didn't mount bigger telescopes and higher resolution instruments because it was already a pain in the rear to transmit data as is.

Sedna is twice that distance away, and the MMRTG will be putting out a lot less power once you get there. You'll have maybe 70 W left. How are you supposed to get any data back at all? Your signal might start to get lost in background noise by that point, and even if it doesn't, you'll need absurd amounts of expensive DSN time to download even one compressed image.

I really think that if we were to start a Sedna mission, we would need to give it more than just a couple watts worth of power, if only to drive the antenna. Give it half a kilowatt instead of 0.07 kW, then we might be talking! Of course, to achieve that, you'd have to provide 0.8 to 0.9 kW at launch. That's comparable to what Cassini-Huygens has onboard. It launched with about 33 kg of plutonium, as opposed to the 4 kg that the MMRTG on Curiosity has. Can your mission proposal deal with purchasing eight times the amount of plutonium? And your spacecraft with four times as much weight dedicated to power generation? Keep in mind that the US may not even have that amount of plutonium in stock, even if you had all the money in the world. You'd have to pay to restart production.

Of course, it might be worth considering to restart the cancelled ASRG program, which aimed to produce a much higher efficiency generator weighing 25% less than a MMRTG, carrying only a quarter the plutonium, yet still producing 140 W as opposed to 110 W. With that thing, yyou could get 840 W power output with just 1/6th the plutonium, with just a slightly worse total weight. And that's assuming you can't scale the unit up for significantly improved power/weight, as RTGs usually do when scaled up. Of course, there's downsides to this too: you'd have to restart and finish the cancelled development program, as mentioned before. And, can you guarantee that the stirling pistons used in these units can survive 20-30 years in deep space without breaking?

So yeah... this is not going to work with an MMRTG. You need much, much more power.

Also, patience may be a virtue here. As much as I want to learn more about Sedna, we can still intercept it at perihelion if we launch around 2050 instead of 2030. Just imagine what kind of technology we might be able to throw at the problem then!

Which is why, case and point, this thing will arrive as soon as or maybe a little later than NH did because of using the Oberth effect.

Also, the probe might be able to use future outer Solar System probes as data relays.

Finally, I will increase it to using 2 MMRTG's to double the power output. NASA has at least enough for 2 MMRTGs not reserved for M2020.

Edited November 7, 2015 by _Augustus_

[Streetwind]

Also, the probe might be able to use future outer Solar System probes as data relays.

I don't think that will work. Signal strength is governed by four things: power input, distance, size of the sending antenna, and size of the receiving antenna.

Future deep space probes will go mostly towards Jupiter, as Europa is one of the key science destinations defined for the near future, along with Mars. Jupiter's SMA is 5.2 AU. Sedna's perihelion is 76 AU, though if you launch 2030 and want to be there by 2040, it won't be at perihelion, so we'll say 80 AU. That means that in the best case scenario, the signal has to travel 75 AU to Jupiter, versus 79 AU to Earth. Considering that those distances are very similar, and the sheer size of the DSN antennas far dwarfs anything that a deep space probe carries, your connection to Earth is always going to be significantly better than your connection to a deep space probe. In other words - deep space probes will likely be unable to even detect, much less resolve a signal coming from Sedna if it is transmitted with just a hundred or so watts of power, and thus won't be able to play relay. You need the DSN to have a chance to catch it.

Even at Saturn, with its SMA of 9.6, you're probably still not far enough away from Earth to make a small portable antenna better than the DSN. Sedna is just that absurdly far away.

Finally, I will increase it to using 2 MMRTG's to double the power output. NASA has at least enough for 2 MMRTGs not reserved for M2020.

2 MMRTGs is still less power than New Horizons launched with, and you want to cover twice the distance. Mind you, I don't know enough to do the math, but I don't believe it'll be enough...

I mean, with the 8 kg of plutonium from two MMRTGs, you can build a single bigger RTG that can output more than the two combined. But to match New Horizons, you need at least 10 kg in a single unit (because that's what NH carried).

Edited November 7, 2015 by Streetwind

[fredinno]

Dark Knight is just one of the three possible boosters for Block II though.

They chose Dark Knight for the future SRBs to replace 5-segs a while ago.

http://www.nasaspaceflight.com/2015/02/advanced-boosters-towards-solid-future-sls

All the infrastructure is being made assuming a solid booster. It would take a miracle for F-1B to be used for SLS, really, as NASA doesn't really have a reason to do that, as advanced SRBs can do the job fjust fine.

- - - Updated - - -

There is no Mercury flyby. It's a Sun close flyby maneuver.

- - - Updated - - -

I don't know if the course correction would need to be that big, as Quaoar itself is big enough to be used for a slight plane change. Both Sedna and Quaoar are fascinating objects (Quaoar is really just icing on the cake), with Sedna being a possible Hills Cloud object or captured rogue dwarf planet.

Furthermore Sedna has odd rotation but no moons, and it could prove or disprove a Trans-Neptunian planet.

Your point about the RTG is excellent, along with the fact that we want mission engineers and the president that orders it's construction to be still alive when it arrives.

And I'll be writing a whole paper on this. Promise.

The Uranus orbiter that is currently the top priority after Europa Clipper has actually begun construction would be a New-Horizons-sized probe that orbits Uranus, and it would be launched on the SLS Block IB or II and be a New Frontiers mission.

There's only 2 boosters left - Dark Knight and that other one. Pyrios is being considered for a future evolved SLS that also uses the J2X though.

Regardless, they will still be making the SLS carry 130t to LEO.

Thank you! I might put some of your info in the paper.

You're welcome.

Not true. SLS Block II will cost about $600 million to build and launch, and WISPIE will be smaller than New Horizons due to shorter flyby time and constraints on payload mass and electricity usage as we need to fit in a starshield and the thing will only use 1 MMRTG, which provides roughly half the power as NH's RTG. This means that the total cost of the probe to build, launch, and fly it should be less than 1.5 billion, which is about the same price as Europa Clipper or M2020.

WISPIE, Europa Clipper and M2020 are quasi-flagship missions, really. A true flagship mission can cost as much as 3 billion.

- - - Updated - - -

Which is why, case and point, this thing will arrive as soon as or maybe a little later than NH did because of using the Oberth effect.

Also, the probe might be able to use future outer Solar System probes as data relays.

Finally, I will increase it to using 2 MMRTG's to double the power output. NASA has at least enough for 2 MMRTGs not reserved for M2020.

Source for SLS block II cost?

Uranus Orbiter is Flagship- that's how it's been designated by the commitee (forgot its name) at NASA.

Also, you would need as much as NH for RTG power,simply due to Sedna's distance.

Edited November 7, 2015 by fredinno

[Kryten]

Uranus Orbiter is Flagship- that's how it's been designated by the commitee (forgot its name) at NASA.

Also, you would need as much as NH for RTG power,simply due to Sedna's distance.

The planetary science decadal committee. They determined you're not going to get a useful orbiter at either ice planet for an NF budget.

[_Augustus_]

I don't think that will work. Signal strength is governed by four things: power input, distance, size of the sending antenna, and size of the receiving antenna.

Future deep space probes will go mostly towards Jupiter, as Europa is one of the key science destinations defined for the near future, along with Mars. Jupiter's SMA is 5.2 AU. Sedna's perihelion is 76 AU, though if you launch 2030 and want to be there by 2040, it won't be at perihelion, so we'll say 80 AU. That means that in the best case scenario, the signal has to travel 75 AU to Jupiter, versus 79 AU to Earth. Considering that those distances are very similar, and the sheer size of the DSN antennas far dwarfs anything that a deep space probe carries, your connection to Earth is always going to be significantly better than your connection to a deep space probe. In other words - deep space probes will likely be unable to even detect, much less resolve a signal coming from Sedna if it is transmitted with just a hundred or so watts of power, and thus won't be able to play relay. You need the DSN to have a chance to catch it.

Even at Saturn, with its SMA of 9.6, you're probably still not far enough away from Earth to make a small portable antenna better than the DSN. Sedna is just that absurdly far away.

2 MMRTGs is still less power than New Horizons launched with, and you want to cover twice the distance. Mind you, I don't know enough to do the math, but I don't believe it'll be enough...

I mean, with the 8 kg of plutonium from two MMRTGs, you can build a single bigger RTG that can output more than the two combined. But to match New Horizons, you need at least 10 kg in a single unit (because that's what NH carried).

They chose Dark Knight for the future SRBs to replace 5-segs a while ago.

http://www.nasaspaceflight.com/2015/02/advanced-boosters-towards-solid-future-sls

All the infrastructure is being made assuming a solid booster. It would take a miracle for F-1B to be used for SLS, really, as NASA doesn't really have a reason to do that, as advanced SRBs can do the job fjust fine.

- - - Updated - - -

There is no Mercury flyby. It's a Sun close flyby maneuver.

- - - Updated - - -

Source for SLS block II cost?

Uranus Orbiter is Flagship- that's how it's been designated by the commitee (forgot its name) at NASA.

Also, you would need as much as NH for RTG power,simply due to Sedna's distance.

2 MMRTGs (I've updated the OP) provide about as much power as the NH RTG. There's also always the possibility that the ASRG could be restarted or an Americium RTG could be used.

And can someone give me a definite answer on a Quaoar flyby?

[Kryten]

And can someone give me a definite answer on a Quaoar flyby?

You're talking hundreds of metres a second to make that change, much more than NH was left with. Definitely flagship class, and a very hard one to justify.

[Streetwind]

Not sure what you're asking exactly in regards to Quaoar. If the position is suitable, and you write that you checked that it does, what else do you need to know? Could you rephrase the question a bit?

[MichaelPoole]

Space exploration is not that expensive. A group of jerks has stolen 2.16 billion Euros from people in my country, Slovakia, or 2.32 billion Euros. That is not conjecture, but amount of money that is being officially discussed in the court proceedings with the people who cheated a big number of people from their money. That is like 3 New Horizon missions. It is a huge travesty that NASA has less money for one mission than a bunch of thieves from a post-communist country of just 6 million people. People who see the word millions and think how expensive space exploration is have no idea about what kind of money are spent in budgets of whole states. After India's MOM mission was launched, many people were condemning India because it is a third world country where many are starving. But let us be honest, would this money really go to the people in such a corrupt country? This amount of money would hardly save the whole India. The whole mission has cost 73 million USD. There are private individuals who would be able to fund something like that from their own pocket, hell, there are mansions more expensive than that. The funding of NASA is a travesty, by all means, space exploration is the cheapest part of a national budget.

Europa is interesting, but without a "ground truth" probe with a drill and a microscope there will be no definite real proof of life, just "maybe this maybe that". Same with Mars, the only probe that actually had a (very primitive) apparatus to detect life was the Viking Lander, which landed on a random location and the apparatus was so unreliable it couldn't detect life in Antartica or desert on Earth despite life being present in those samples. Instead of doing half hearted searches and obsessing over possible microbes, maybe we should go somewhere unseen and unexpected. Maybe I am weird, but I do not think space exploration should be a desperate search for life in our immediate neighbourhood. If you want to do that, at least do it right. Send out probes that can actually detect life.

Edited November 7, 2015 by MichaelPoole

[More Boosters]

Space exploration is not that expensive. A group of jerks has stolen 2.16 billion Euros from people in my country, Slovakia, or 2.32 billion Euros. That is not conjecture, but amount of money that is being officially discussed in the court proceedings with the people who cheated a big number of people from their money. That is like 3 New Horizon missions. It is a huge travesty that NASA has less money for one mission than a bunch of thieves from a post-communist country of just 6 million people. People who see the word millions and think how expensive space exploration is have no idea about what kind of money are spent in budgets of whole states. After India's MOM mission was launched, many people were condemning India because it is a third world country where many are starving. But let us be honest, would this money really go to the people in such a corrupt country? This amount of money would hardly save the whole India. The whole mission has cost 73 million USD. There are private individuals who would be able to fund something like that from their own pocket, hell, there are mansions more expensive than that. The funding of NASA is a travesty, by all means, space exploration is the cheapest part of a national budget.

Europa is interesting, but without a "ground truth" probe with a drill and a microscope there will be no definite real proof of life, just "maybe this maybe that". Same with Mars, the only probe that actually had a (very primitive) apparatus to detect life was the Viking Lander, which landed on a random location and the apparatus was so unreliable it couldn't detect life in Antartica or desert on Earth despite life being present in those samples. Instead of doing half hearted searches and obsessing over possible microbes, maybe we should go somewhere unseen and unexpected. Maybe I am weird, but I do not think space exploration should be a desperate search for life in our immediate neighbourhood. If you want to do that, at least do it right. Send out probes that can actually detect life.

As people who are here for similar reasons I'm sure most of us would share your sentiment but you also need to realize that space just isn't that interesting to people that aren't interested in it... Sounds like a tautology until you realize that's most people. And being interesting here is also about political and/or financial gains.

[_Augustus_]

Not sure what you're asking exactly in regards to Quaoar. If the position is suitable, and you write that you checked that it does, what else do you need to know? Could you rephrase the question a bit?

I mean, can a flyby be done cheaply without huge course corrections after to get to Sedna?

Quaoar has the same composition of Sedna and studying it might allow us to determine if Sedna is just disturbed from a normal KBO or SDO orbit.

[Robotengineer]

Where are you going to get the plutonium? If we are lucky enough to have a Uranus or Neptune flagship mission a lá Cassini, we probably won't have enough plutonium for any other missions (AFAIK). To get two MMRTG's for one mission would be outrageous. What instruments would you want to send? What is your weight limit?

[MichaelPoole]

As people who are here for similar reasons I'm sure most of us would share your sentiment but you also need to realize that space just isn't that interesting to people that aren't interested in it... Sounds like a tautology until you realize that's most people. And being interesting here is also about political and/or financial gains.

I think most people are also not interested in getting ripped off, yet even rip off artists get more money than space exploration. It also depends on the culture and education - my mom grew up in USSR's countryside in conditions a lot more modest than what majority of people here ever lived in, but they had Astronomy as a separate subject in school, visited planetariums etc. I am not somebody to defend a country like the USSR with the obvious many faults and crimes of its goverment, but I think people should be educated and have a certain "general knowledge". I personally think the modern world is being harmed by the focus of society on the fictional and artificial entertainment instead of reality. I think our future is in space and that knowledge uplifts the human spirit and this is one of the few things I must say I agree with the USSR's idea on this issue. Sure, you don't need to know anything about space. Technically speaking we don't even need higher intelligence as most creatures do okay without it. However, I think such an existence would be a very impoverished one. Furthermore, even in a democracy, mob rule should not set the priorities. NASA and other space agencies deserve enough money to be able to fulfill their scientific goals. I don't think the Average Joe wants fighter jets either yet they are even more expensive than spacecraft. There are many things that are funded that the average person wants less than spaceships.

Also, the power problem could be solved by a nuclear reactor. It was tried before by the USSR.

[_Augustus_]

Where are you going to get the plutonium? If we are lucky enough to have a Uranus or Neptune flagship mission a lá Cassini, we probably won't have enough plutonium for any other missions (AFAIK). To get two MMRTG's for one mission would be outrageous. What instruments would you want to send? What is your weight limit?

This would either use Americium RTGs, ASRGs, or replace the ice giant orbiter.

The upper mass limit is about 500-600 tons.

The scientific payload would include a spectrometer, camera, and dust counter.