As an attendee at the Royal Institute in London for the 30th May 2015 Mission Control meeting I had opted for the Mission Technology Lab Stream. In the time we had available we managed to produce a list of things to consider throughout the Delivery Phase of the Mission (getting the probe to the Lunar surface.
I attach a pdf file which is a report generated mostly from my notes and some minimal research on-line afterwards (mainly for launch vehicle stats). I would hope that we can get some follow-on meetings where we can put a bit more flesh on the bones.
Anyway, I submit the following brief report which is in the form of a Task List with added notes. It is a start.

Paul E. Bennett IEng MIET
Systems Engineer
HIDECS Consultancy

Thank you for these comprehensive concise notes.

Thank you Paul, it was a pleasure to meet you and Jürgen on Saturday.

Hi everyone,

I also attended the lab2 (first session) and I appreciate the good summary of the session. To help start the discussion I would like to add a few comments about what the options were and the subdivision into these stages. During the presentation I think it sounded like the different stages were separate problems to solve, which might cause us to think inside these boxes, when solution to each problem actually affects the problems of later stages.

For instance, concerning how to get from Low Earth Orbit (LEO) to Low Lunar Orbit (LLO), one of the two options mentioned is to use a conventional chemical rocket to turn the round low orbit into an elliptical one where the high point (apogee) reaches the Moon's orbit around Earth ("Hohmann transfer orbit"), perform mid-course corrections, and then fire a rocket again at apogee in order to catch up with the Moon's speed. The chemical propellant weighs (=costs) more but getting there quicker reduces the time spent in the harsh environment that space is.
The alternative, going with low thrust like solar sails or ion engines, would take longer BUT save propellant mass ("=money"), the course-corrections would be an integral part of the trajectory, and both the insertion into LLO, AND the proposed orbital maneuvers to get better images of the landing site, would all be done with the same system all the way from LEO, which would reduce complexity. Because of the low fuel consumption it would also increase our options to modify the plan to get better images or landing approach vector after the initial scans. However, we will still need a big chemical thruster for the landing, but much less fuel for it. So there are plenty of trade-offs.

My point is, that the different stages of the delivery can't be problem-solved in isolation. Even the landing method's impact on the following science experiments which we haven't even started with must also be considered so e g the rocket-plume doesn't create an hard crust that we have trouble drilling through. That's why I think we initially should sort out the high-level functional requirements and uncertainties first. "Get from LEO to LLO and still be able to study the landing area and land" and "Land softly enough that is no essential equipment breaks, and still be able to drill where the probe can reach" are pretty certain, but e g "Do a Mid-Course Correction to get optimal approach vector" will only be a task if we go with the high-thrust option. And we need to recognize that we are in for surprises when we scan for landing sites and plan the landing, so we should leave room for re-planning.

Once again, thanks for getting the discussion started!

/Lars Sjödahl

lake5855 wrote: Hi everyone,
I also attended the lab2 (first session) and I appreciate the good summary of the session.
/Lars Sjödahl

Thanks all, appreciation of my initial effort is quite welcome.

lake5855 wrote: To help start the discussion I would like to add a few comments about what the options were and the subdivision into these stages. During the presentation I think it sounded like the different stages were separate problems to solve, which might cause us to think inside these boxes, when solution to each problem actually affects the problems of later stages.
/Lars Sjödahl

Whilst they are not generaly separate boxes, they can be thought of as interface points which, at their juncture, demand that a specific contractual agreement is reached on the conditions for a transition. So, while the same systems might be operational throughout all those stages, there is a notional change of mode of operation to consider.

lake5855 wrote: For instance, concerning how to get from Low Earth Orbit (LEO) to Low Lunar Orbit (LLO), one of the two options mentioned is to use a conventional chemical rocket to turn the round low orbit into an elliptical one where the high point (apogee) reaches the Moon's orbit around Earth ("Hohmann transfer orbit"), perform mid-course corrections, and then fire a rocket again at apogee in order to catch up with the Moon's speed. The chemical propellant weighs (=costs) more but getting there quicker reduces the time spent in the harsh environment that space is.

The alternative, going with low thrust like solar sails or ion engines, would take longer BUT save propellant mass ("=money"), the course-corrections would be an integral part of the trajectory, and both the insertion into LLO, AND the proposed orbital maneuvers to get better images of the landing site, would all be done with the same system all the way from LEO, which would reduce complexity. Because of the low fuel consumption it would also increase our options to modify the plan to get better images or landing approach vector after the initial scans. However, we will still need a big chemical thruster for the landing, but much less fuel for it. So there are plenty of trade-offs.
/Lars Sjödahl

Space will always be a demanding environment but we have knowledge of technology that is capable of surviving for extended periods in a space environment (see Rosetta and Philae for example) . However, the Lunar surface, and the journey down from LLO, is where the probe will face the greater risks. Spending more time on the journey is not going to be as major a problem as some think.

lake5855 wrote: My point is, that the different stages of the delivery can't be problem-solved in isolation. Even the landing method's impact on the following science experiments which we haven't even started with must also be considered so e g the rocket-plume doesn't create an hard crust that we have trouble drilling through.

lake5855 wrote: Which might require shutting off the descent engine before we actually land and letting the last bit be a free-fall. That will require shock absorbing landing struts that could survive such an impact (meaning heavier structural dead-weight).

lake5855 wrote: That's why I think we initially should sort out the high-level functional requirements and uncertainties first. "Get from LEO to LLO and still be able to study the landing area and land" and "Land softly enough that is no essential equipment breaks, and still be able to drill where the probe can reach" are pretty certain, but e g "Do a Mid-Course Correction to get optimal approach vector" will only be a task if we go with the high-thrust option. And we need to recognize that we are in for surprises when we scan for landing sites and plan the landing, so we should leave room for re-planning.
/Lars Sjödahl

From the discussion on Saturday it seemed like they were thinking we would do the more stable Polar Lunar Orbit for as long as we needed to in order to gather images, transmit them back and analyse the results. The very low pass orbits would be limited in number to minimise the risk of collision with high mountains but to add finer grain detail for final landing site selection. returning to the stable Polar Lunar orbit, where we have time to analyse for our best options, We would only commit to the final descent when we were ready.

lake5855 wrote: Once again, thanks for getting the discussion started!
/Lars Sjödahl

...and thankyou for your thoughts.

Here is hoping that the link will work for everyone. This is a talk by Dr. Robert Bond on Skylon and the work at Reaction Engines Ltd.
< email.ietinfo.org/c/1j41M021MyDZ3ik5WEEOYFYjwt >
It is about an hour in length but is well worth the view.