Discussion Uranus and Neptune mission concepts

[Urwumpe]

I can imagine that the data from the probe can require time to be transmitted, long time to be interpreted and very long time to be utilized for a safe and reliable entry path...
Months (or even years) of distance from the two probes could be needed, IMHO

Exactly - the loop would be pretty long, also you just get ONE snapshot of the atmosphere by a reentering probe - together with more measurements from other sensors or missions, you can get a more accurate atmosphere model, but that takes some weeks time.

Possible would be a two-part mission: An atmospheric probe and a small orbiter for a first science season, and a larger aerobraked orbiter for a longer second season, launched on the next launch window. This way you can also get much more science than from a single mission with many compromises on trajectory planning and possible payload (and consumables).

 

[K_Jameson]

Possible would be a two-part mission: An atmospheric probe and a small orbiter for a first science season, and a larger aerobraked orbiter for a longer second season, launched on the next launch window. This way you can also get much more science than from a single mission with many compromises on trajectory planning and possible payload (and consumables).

Interesting solution, but, always with an eye on the realism, a double launch towards Neptune (and only for allowing aerocapture for the second mission) sounds prohibitive in term of costs...

 

[Urwumpe]

Interesting solution, but, always with an eye on the realism, a double launch towards Neptune (and only for allowing aerocapture for the second mission) sounds prohibitive in term of costs...

Well, I think the next really good launch window would be in 2034 anyway, 13 years later... so that's a good time frame for two such missions.

 

[K_Jameson]

Also, sorry to be off topic, but why has there been no Orbiter Live Missions since November 2013? I just don't know where else to ask.

Because Fausto, our "radio host", got married! :rofl:

 

[Nicholander]

Oh. (It probably said something about that in Forum Orbiter Italia, but, of course, it's all in Italian.) Anyway, I think the idea of 2 Uranus probes is interesting, but how much mass do you think the smaller one with the atmospheric probe would have? And what's the smallest Jarvis that can get it to a Trans Jovian Injection?

 

[K_Jameson]

Anyway, I think the idea of 2 Uranus probes is interesting,

The idea of two distinct missions was actually considered for Neptune :thumbup:
For Uranus, Shakespeare/Pope is the definitive mission. In reality, i think that, for Neptune, a Shakespeare twin should be the most logical choice. The aerocapture mission will be perhaps rerouted at Titan. If will ever come.

but how much mass do you think the smaller one with the atmospheric probe would have? And what's the smallest Jarvis that can get it to a Trans Jovian Injection?

Here a rough estimate of the Trans Jovian performance for every FOI rocket:

Quasar 452: 22,000 kg
Quasar 440: N/A
Quasar 220: N/A
Jarvis M: 14,000 kg (selected launcher for Galileo II)
Jarvis H: 8,000 Kg
Jarvis E: 4,500 Kg
Jarvis B: N/A
Jarvis C: 3,000 Kg (selected launcher for Shakespeare/Pope)
Jarvis L: N/A
Jarvis S: N/A
Neptune 1B+Fregat: 450 kg
Neptune 1B: N/A
Neptune 1+Fregat: 250 kg
Neptune 1: N/A
Triton 1: N/A

Thus, depending on the mass of the hypotetical atmospheric probe, a Neptune 1 or 1B with a Fregat upper stage can be sufficient for the job. Being Fregat a low thrust and long burn stage, such a mission can require a multi-stage TJI with several sequential burns at the perigee of the initial Earth orbit, instead of a single massive burn.

 

[Nicholander]

Hmm... Would it be feasibly possible to make a 450 kg Neptune Orbiter? (Perhaps that should just be a flyby while dropping the probe, though this little mission is just hypothetical.)

 

[Urwumpe]

Hmm... Would it be feasibly possible to make a 450 kg Neptune Orbiter? (Perhaps that should just be a flyby while dropping the probe, though this little mission is just hypothetical.)

Sure - but aside of a RTG, there is little mass then left for scientific payload.

 

[kamaz]

You guys saw these?

http://sites.nationalacademies.org/cs/groups/ssbsite/documents/webpage/ssb_059323.pdf

http://repositories.lib.utexas.edu/bitstream/handle/2152/26209/LU-MASTERSREPORT-2014.pdf?sequence=1

 

[ISProgram]

Hmm... Would it be feasibly possible to make a 450 kg Neptune Orbiter? (Perhaps that should just be a flyby while dropping the probe, though this little mission is just hypothetical.)

Well, New Horizons is 478 kg: the GPHS-RTG by itself is 56 kg, and the complete instrument mass is 31 kg.

Not exactly feasible, due to a very limited instrument suite, delta-V capability (NH had 290 m/s post-launch), and necessary minimum size for the main structure.

So what Urwumpe said. However, a more efficient energy source, like A MMRTG or the ASRG, might add some margin.

 

[K_Jameson]

You guys saw these?

http://sites.nationalacademies.org/cs/groups/ssbsite/documents/webpage/ssb_059323.pdf

http://repositories.lib.utexas.edu/bitstream/handle/2152/26209/LU-MASTERSREPORT-2014.pdf?sequence=1

The first link is not working.
The second link is interesting. I've never read it before.
The separate chemical propulsion module is a clever mode to optimize the masses: you can use it only for the UOI, then discard it, and stay only with a small and agile orbiter that has only the fuel for the orbital corrections. But sounds a little more complicated than a monolithic spacecraft, with a crucial staging event after a decade of flight, and ultimately, IMHO, with more costs. Also, i don't like these RTG so deeply integrated in the shell. That configuration could have some advantages, but i prefer to keep it well away from the body of the spacecraft and especially from the scientific instruments, for minimize thermal and other interferences. On Shakespeare, RTG are isolated and 120 degrees away from the main science package.

---------- Post added at 12:12 PM ---------- Previous post was at 11:01 AM ----------

Hmm... Would it be feasibly possible to make a 450 kg Neptune Orbiter? (Perhaps that should just be a flyby while dropping the probe, though this little mission is just hypothetical.)

MESSENGER spacecraft weighs 485 kg; i don't know exactly what is the total Delta V capability of that spacecraft and thus the fuel fraction, but giving this precedent, i think that a very (VERY) minimal Neptune orbiter can stay in the 450 kg budget. Such an orbiter will have really basic capabilities and i don't think that it's worth of the effort.

But in my precedent post i have misunderstood. I meant 250/450 kg exclusively in reference to an atmospheric probe. Past atmospheric probes ranges from 90/95 to 300/350 kg; with a minimal cruise stage, a probe-only mission can IMHO reenter in the given weight.

 

[kamaz]

The first link is not working.

Same here... but it worked yesterday. Try again on Monday It's a Uranus mission study done as a proposal for Planetary Decadal Survey in 2011. The main site (when it works) is at http://sites.nationalacademies.org/SSB/SSB_059331

Some more:
http://solarsystem.nasa.gov/docs/4....e Giant Planetary Origins Probe (Ice-POP).pdf
http://www.lcpm10.caltech.edu/pdf/session-5/1_Uranus-Explorer-LCPM-130618-Matousek-final.pdf
http://www.lpi.usra.edu/opag/jan201...y2/01_Hofstadter_UranusWorkingGroupReport.pdf
https://www2.le.ac.uk/departments/physics/news/rasuksm/talks/12- csa_ras_uranuspathfinder_v0.pdf

NB it appears that the person behind the Uranus proposal was this guy:
https://science.jpl.nasa.gov/people/Hofstadter/ ... I would consider sending him a nice e-mail asking if he has any stuff you could find useful

 

[K_Jameson]

Same here... but it worked yesterday. Try again on Monday It's a Uranus mission study done as a proposal for Planetary Decadal Survey in 2011. The main site (when it works) is at http://sites.nationalacademies.org/SSB/SSB_059331

Some more:
http://solarsystem.nasa.gov/docs/4....e Giant Planetary Origins Probe (Ice-POP).pdf
http://www.lcpm10.caltech.edu/pdf/session-5/1_Uranus-Explorer-LCPM-130618-Matousek-final.pdf
http://www.lpi.usra.edu/opag/jan201...y2/01_Hofstadter_UranusWorkingGroupReport.pdf
https://www2.le.ac.uk/departments/physics/news/rasuksm/talks/12- csa_ras_uranuspathfinder_v0.pdf

The Uranus orbiter is a project that was in my mind from long time - maybe two years. Over this time, i downloaded and read several documents about proposed Uranus missions, included the ones you posted here (many thanks anyway!).
I can say that the overall configuration of my spacecraft is more or less "frozen" at this point. It is a matter of configuration, packaging and release...

As stated, my interest in developing is moving on Neptune and/or Titan. For Neptune, a duplicate of the Uranus mission can be the better and most realistic solution, but perhaps a little "boring" because it is something "already done". This is the main reason that leads the aerocapture idea: triying something different.

NB it appears that the person behind the Uranus proposal was this guy:
https://science.jpl.nasa.gov/people/Hofstadter/ ... I would consider sending him a nice e-mail asking if he has any stuff you could find useful

Great! Maybe i can send a mail with the specifications of my spacecraft and ask if it appears to be sufficiently realistic!

---------- Post added at 07:11 PM ---------- Previous post was at 02:25 PM ----------

Integration test of Shakespeare-pope with the Jarvis C upper stage, via custom payload adapter.

Internal configuration of Shakespeare with the N2O4 and MMH tanks, reaction wheels (3+1 spare), helium bottles and auxilliary hydrazine tanks.

 

[Nicholander]

Cool, development pics. Anyway, I did a little calculation on the hypothetical 450 kg Uranus atmospheric probe, so assuming the atmospheric probe itself has a mass of 350 kg, the cruise stage 50 kg, 50 kg of fuel, and an isp of 300 s, this gets 346.635 m/s of delta-v. Is that enough to get a collision course with Uranus? (This DV is for course corrections, obviously) (Assuming that this doesn't orbit, just drops the atmospheric probe on a collision course with Uranus)

 

[kamaz]

http://sites.nationalacademies.org/cs/groups/ssbsite/documents/webpage/ssb_059323.pdf (it works now), page 41:

To accommodate science using an entry probe, the probe must be released prior to UOI on an entry trajectory to the planet. Achieving a safe UOI outside the rings with the lowest possible periapse of 1.3 RU puts significant constraints on the probe entry conditions. The design was established to release the probe 29 days prior to Uranus arrival, allowing enough time for a deflection burn with the orbiter at a modest delta-V of 30 m/s 28 days before arrival. This geometry (shown in Figure 3-9) allows 1 hour of
viewing the probe’s descent within the atmosphere with another hour to prepare for UOI.

Doing this maneuver in Orbiter may be... challenging.

---------- Post added at 11:52 PM ---------- Previous post was at 11:45 PM ----------

See also p. 149 and following.

 

[K_Jameson]

Nicholander talks about a probe-only mission. In my understanding, the cruise stage will be discarded after the probe release, and no further correction (and no UOI) are planned. The stated Delta-V is IMHO sufficient for the job, although we have another problem: without an orbiter to act as communication relay, the direct data transmission via low gain antenna of the probe can be extremely difficult (think at the bandwith and power trasmission allowed by the Galileo low-gain antenna at Jupiter and divide it for eight, giving the Uranus distance - perhaps a barely audible signal).
The atmospheric capsule must be equipped with a medium or high gain antenna, or the cruise stage must act as relay before its disintegration in the Uranus atmosphere. This require a significant difference in velocity between the two spacecraft, allowing the arrive of the probe in the atmosphere well before the cruise stage and giving the time for the data trasmission from the probe to the cruise stage e from the cruise stage to Earth.

Even in my project, timing is crucial. Unlike Galileo, Shakespeare is not equipped with a secondary antenna for data relay, and the entire spacecraft must be turned to Uranus during the 90 kg probe descent, using the main antenna as receiver. This does not allow to correctly orientate the main engine for the UOI, and thus the two jobs can't be performed at the same time. The probe must arrive well before the time for the orbiter's UOI maneuvre.

 

[Nicholander]

Hmm... So the cruise stage should then, after separating the atmospheric probe, change it's course so it gets a periapsis over where the probe is so it can relay data... Good idea, K_Jameson! (Also, I've been thinking, why not have the atmospheric probe and flyby cruise stage be for Neptune, and I've even calculated the trajectory here, I'd go with the 2018 launch one.)

 

[kamaz]

without an orbiter to act as communication relay, the direct data transmission via low gain antenna of the probe can be extremely difficult (think at the bandwith and power trasmission allowed by the Galileo low-gain antenna at Jupiter and divide it for eight, giving the Uranus distance - perhaps a barely audible signal).

The PDS proposal says that transmission via low-gain antenna from Uranus is impossible.

In this proposal the probe talks to orbiter, which later performs "blind" orbital insertion, orients high-gain antenna towards Earth, and then relays data.

Even in my project, timing is crucial. Unlike Galileo, Shakespeare is not equipped with a secondary antenna for data relay, and the entire spacecraft must be turned to Uranus during the 90 kg probe descent, using the main antenna as receiver. This does not allow to correctly orientate the main engine for the UOI, and thus the two jobs can't be performed at the same time. The probe must arrive well before the time for the orbiter's UOI maneuvre.

The PDS proposal uses the same approach. The time between end of probe's mission and start of UOI is 1 hour.

Hmm... So the cruise stage should then, after separating the atmospheric probe, change it's course so it gets a periapsis over where the probe is so it can relay data...

So you can use the same encounter geometry the PDS proposal has. Except that you do not do the orbital insertion burn, the cruise stage simply flies past Uranus.

 

[K_Jameson]

The PDS proposal says that transmission via low-gain antenna from Uranus is impossible.

I agree (although I read that the Huygens low-gain signal was directly detected on Earth... well, Saturn is much closer than Uranus) . This is why, as backup, besides the two low-gain omni, Shakespeare has a medium-gain antenna on top of the high-gain!

---------- Post added at 10:59 AM ---------- Previous post was at 10:48 AM ----------

Hmm... So the cruise stage should then, after separating the atmospheric probe, change it's course so it gets a periapsis over where the probe is so it can relay data... Good idea, K_Jameson! (Also, I've been thinking, why not have the atmospheric probe and flyby cruise stage be for Neptune, and I've even calculated the trajectory here, I'd go with the 2018 launch one.)

Earth-Neptune in less than ten years! f*****g fast!
Your launch window requires a very close Jupiter flyby, closer than Io... a radiation hell... that can require some sort of protection although it is an one-shot pass. The only probes that had performed a so close flyby with Jupiter was Pioneer 10 and 11. They weren't shielded and suffered various problems during the maneuvre.

I suggest a launch window with a bit more relaxed Jupiter flyby. Anyway... such a fast trajectory is perfect for my aerocapture concept... I'm not afraid with the high velocity encounter, because I do not have to load the fuel for a NOI propulsive maneuvre.

I have modified the thread title!

---------- Post added at 11:55 AM ---------- Previous post was at 10:59 AM ----------

Some comparison.

Shakespeare/Pope (at center) with the sister ship Efesto (left) and Galileo II (right). Galileo II has a total mass, fully fueled, of 12,731 kg.

Sub-probes comparison. Pope (at center) with the Efesto atmospheric probe for Venus (left), showed with detachable aeroshell, and "Salviati" lander for Europa (right) with its Star-27H braking stage.
Pope is a simple probe without detachable aeroshell and only with a minimal parachute. Efesto atmospheric probe has a more substantial science package, two-stage parachute, detachable aeroshell and backshell, and landing capability.

 

[Nicholander]

Yes, less than 10 years is stupidly fast! Hmm... The radiation is a concern, but I assume you're talking about the 2018 launch window? That has a Jupiter pass radii of 2.88, but the 2019 launch window has a pass radii of 10, out of the Jovian radiation belt, I presume. (Feel free to correct me) And it gets the probe to Neptune in 9.55 years, not 9.99! But, however, it requires more delta-v for the trans-Jovian injection burn, 7.07 km/s instead of 6.75 km/s. How much would the Neptune be able to get with a 7.07 km/s injection burn?