Conceptual Sample Return Mission to a Comet/Asteroid (IPSA CASR)

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Was mulling over whether or not to make this thread, considering how previous ones went. As you can see, I have made the (possibly?) regrettable mistake of making a thread.

Not on a rocket question, but a mission concept for sample return! From a asteroid and/or comet, no less, given the recent craze surrounding ESA's Rosetta mission to 67P/Churyumov–Gerasimenko AND JAXA's upcoming Hayabusa 2 mission to (162173) 1999 JU3.

So yeah, I'm a fan of comets/asteroids, sue me. :)

This, by the way, is an in-universe mission conducted by my fictional space agency IPSA (International Partnered Space Agenda). To quote an earlier update:

The goal of the IPSA Comet-Asteroid Sample Return (CASR) proposal is to expand upon experience gained by ARCHIMEDES and to return samples from, and characterize, a designated minor planet body. CASR will target either a comet or an asteroid, with the potential to rendezvous with a NEO of the latter option. If time permits (and I hope it does), CASR will/may branch off into TWO separate mission in-universe, so that both an asteroid and a comet are visited.

The illustration above below shows the baseline spacecraft as it is currently envisioned at the moment.


The baseline proposal and its baseline criteria/prerequisites:

1) CASR will target either a comet or an asteroid. An extended mission to another minor body after delivery of the samples back to Earth is possible, but not part of baseline mission at this point.

2) Earth reentry velocity for the return capsule is Not To Exceed (NTE) substantially from 12.9 km/s, the record set by the NASA Stardust mission on January 2006 (the upcoming OSIRIS-REx mission will have a 2023 reentry at around 12.4 km/s). This may change if other heat-shield material (PICA-X, for example) is shown to be capable of enduring this speed and resulting heat load (14 km/s is acceptable, 28 km/s is definitely not, at the moment).

3) The return capsule will be derived from a previous sample return mission. The baseline spacecraft uses one similar to that of Stardust. If I can acquire specifications for the OSIRSIS-Rex capsule, that may be used instead.

4) Preferably, the spacecraft will launch on the Aquarius B1, in particular the previously unrevealed triple core configuration. While this is definitely overkill, with at least 60mT expected out of this configuration, the spacecraft mass and its calculated transfer orbit may warrant this. Another rocket referred to as the Verseau, which is still in development, is also an option. I strongly prefer an IPSA launch vehicle. The real-life Atlas V is also an option at the moment, if it’s not retired before the expected launch period.

5) The mass of the complete spacecraft, not including the necessary adapters to fit it to the launch vehicle, is NTE 5,000 kg fully fueled. This is why it might need the Aquarius Heavy, which is still a little overkill for the mass.

6) The spacecraft is to have at least 2,000 m/s of delta-V by itself. This may go up or down, depending on the evolution of the mission proposal.

7) The mission must launch in the 2027-2037 period. The upper limit of this period coincides with an early launch of the Aquarius B1; a later date is also okay.

8) Launch may occur from either Ominke Atoll (Kuria Island) or Cape Canaveral (Florida). Only the latter launch site will support the Aquarius. There are no pads for Aquarius at Ominke due to spacing issues.


So those are the baseline criteria for the mission. A few of these criteria may need to be relaxed or constrained depending on the exact mission profile, which is still pending. A few targets have already been selected as well, though there will be more. Those targets are:

Asteroid 153591 (2001 SN263)

Asteroid 2014 HN2

Comet P/2010 K2 (WISE)

Comet 72P/Denning-Fujikawa

Comet 289P/Blanpain

Comet D/1894 F1 (Denning)

Comet 45P/Honda-Mrkos-Pajdusakova


Now, I strongly want for CASR to go to a comet. I love comets. Comets are interesting. There’s a freaking Comet Observatory in Super Mario Galaxy! However, the scientific return of a comet must be weighed against that of an asteroid, as well as making sure that as many of the aforementioned criteria are fulfilled. An asteroid is more reasonable than a comet as a result.

The specific spacecraft criteria for a asteroid destination:

1) Stay time at the asteroid can be as short as 112 days (Hayabusa was at 25143 Itokawa from September to November 2006 per the modified mission profile) to as long as 4 years. Frankly, there is no upper limit for the stay time, longer is actually better.

2) The baseline sample acquisition method will be “touch-and-go” (as pioneered by Hayabusa and to be utilized on OSIRIS-Rex and Hayabusa 2), where the spacecraft will approach and contact the asteroid surface with the acquisition mechanism.

3) The target asteroid’s orbit is NTE an aphelion (farthest point from the Sun) of 5 AU. That’s Jupiter’s distance, for crying out loud. A Near Earth Object’s orbit is much closer to home, so NEO asteroids have a priority over that of other asteroids (like those in the asteroid/main belt). Bad for Earth and possibly humanity), good for delta-V budget.

4) The baseline mission length for an asteroid is NTE 7 years.

5) Asteroids have types. Comets do not. A C-type asteroid is a particularly high priority target, though others are also acceptable.

6) As mentioned before, spacecraft delta-V is to be at least 2,000 m/s. However, ion propulsion is also considered possible, so a spacecraft delta-V of 10,000 m/s is also possible for a main belt target.


Now the specific criteria for a comet destination:

1) Stay time at the comet can be as low as 112 days up to 4 years. Once again, there is no upper limit, as long as possible is preferred. Preferably the stay time at the comet is close to, if not more, than its orbital period. This allow the spacecraft to characterize the comet environment during the target’s year (comet years are generally 2+ Earth years), so it can see what changes (development of a coma, for example) occur and when as the comet moves on its elliptical orbit.

2) The baseline sample acquisition method will be “touch-and-go”, same as the asteroid. However, this has never been done on a comet, and not a lot of comets have been studied up close (the first mission to orbit a comet is Rosetta, currently around 67P/Churyumov–Gerasimenko) and the surface characteristics of comets is completely understood (the Philae lander from Rosetta will land in 4 days’ time from the posting of this, and it might answer some questions), and CASR cannot return comet ice, if that is on the surface, back to Earth. It has to be rocks or dust. For this exact reason, an aerogel sample acquisition method might be used instead; the mission might have to revert back to a simple flyby mission in order to achieve this.

3) The target asteroid’s orbit is NTE an aphelion (farthest point from the Sun) of 5 AU and an aphelion (closest point) of 0.3 AU. There’s one early candidate that got that close (though I forgot what it’s named), and the spacecraft cannot be made to have to have to survive cold temperatures at aphelion and scorching temperatures at perihelion; it’s just not plausible. You would need a dedicated sunshield, and that takes up payload mass.

4) The baseline mission length for a comet is NTE 10 years.

5) Delta-V is essentially the same as asteroid proposal.

Now that’s about it for the mission-specific criteria. Notably, a comet has a few more challenges than an asteroid. But there’s more!


Optional criteria for either destination:

1) Preferably, the trajectory includes a planetary flyby and a deep space maneuver (DSM). This is merely a preference, though I will admit it is a decision making factor as to which target will be chosen.

Piggyback payloads are not part of the baseline spacecraft, though they might be. This means that along with CASR, a secondary spacecraft also rides to the comet. This could be a payload riding the same upper stage or a dedicated spacecraft attached to CASR itself. This can include landers, satellite, nanorovers, hoppers, etc.

There is no plan at this time to make this into an add-on, still have to finish Aquarius B1 (which will get a development thread when I run into a problem).

As I mentioned before, I was hesitant to make this thread and just do the mission myself. However, I kind of realized that to do it myself (at least to myself) seemed kind of biased, since I was the only one actually planning it.

I think I should get a larger opinion for input in this conceptual mission, hence the reason for this thread. One example being, the type of target selected for sampling, and then the specific body out of that.

You can use Trajectory Browser to find a specific body, if you wish to do so. I will be using the Delta-V Calculator and Silverbird for spacecraft dry mass, instruments, etc. evaluation.

Right now, I'm leaning towards an asteroid sample return, as much as I love comets. Thanks in advance for any help!

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