Lunar MER?, What could a mission like this do? Options

[JRehling]

As plans to explore the Moon move forward, I wondered about the possible success of MER-like rovers sent to the Moon. There are a number of contrasts with Mars:

The same "drive train", in half of martian gravity, could easily carry a much larger set of instruments.

Communications would be almost instantaneous.

Rovers on the lunar near-side would ALWAYS be in radio contact with Earth. No relays necessary.

The lunar sol is 14 days.

Combine those last three points, and you could imagine HUGE (by MER standards) drives performed in a single sol. Or a large number of IDD explorations in a modest-sized area.

The rover would have to survive a lunar night. Some of the mass advantage could be put into heaters.

(Apparently) no issue with dust covering the solar panels.

No seasons. No winter.

Twice the solar power, all things being equal.

MER fans ought to drool. Downside, of course: the Moon may not be as interesting for you as Mars. But there's still plenty there to study.
Operations wise, imagine two "packs" of rovers (a pack could be as small as one rover) sent to different latitudes but the same longitude. Send one pack to someplace near the eastern limb and somewhere near the western limb, so that the fraction of the time that one pack would be in in daylight would approach unity. Have three or four teams on Earth that operate 8 hour shifts to keep each rover in constant action throughout the lunar day. When night falls on one pack, it would not be long until the other pack experienced dawn.

Without the delta-v requirements of interplanetary cruise, it should easily best the cost of MERs. For the launch cost of a New Frontiers mission, two pairs of rovers could be launched to support this kind of exploration, and could last seemingly indefinitely. Four sites with very long drives at each could explore a great variety of the lunar service.

[djellison]

To be honest - while the idea is quite romantic - there's probably little you would end up feeding forward from the MER design into a lunar rover. The requirements are quite different - particularly thermally I'd have thought. You would want realtime video requiring serious bandwidth etc etc. Perhaps the mobility system could be used - but not much else I wouldn't have thought. I seem to remember this debate already happenign though

Doug

[helvick]

I tend to agree with Doug here. While a MER type rover with minimal changes _could_ probably operate on the Moon a lot of the Rover's systems would be redundant or seriously underutilized.

More importantly the entire delivery system would need to be totally overhauled which in turn would change the design constraints on the vehicle. That alone would probably make delivering a "MER" to the moon a relatively inefficient and expensive exercise.

Does anyone have a back of the envelope mass budget estimate for landing material on the Moon? Roughly what sort of launcher do we need to get a few hundred kg softly onto the lunar surface? And once there how expensive is the remote comms likely to be?

And finally even if this was a relatively simple and cheap thing to do would this be a smart way to spend money?

[dvandorn]

Honestly, as much as I would *really* love to see some robotic lunar exploration in the pipeline, I don't think that robotic rovers are the best investment for what we need from the Moon at this point, scientifically.

What would be most useful in terms of unraveling the remaining mysteries of the Moon, IMHO, would be a fleet of small sample return missions. Something like the Luna 16 plan -- able to pull a core up from next to the lander and return it to Earth.

I think the most valuable science you could do at the Moon right now would be to get more samples back here that you could date. We need to be able to pin down the extent of the Late Heavy Bombardment and the range of ages of the maria, and while we have some decent ballpark figures, we don't know very well when all the various basins were emplaced. That information, and data on how long the Moon was volcanically active, can only really be derived from dating of samples. And since the current technology doesn't really let you date the samples in situ, we need to bring them back here.

Now, from an engineering standpoint, rovers make good sense. If you're planning on building a lunar base (or a lunar resort hotel), it would be great to send a bunch of robotic surveyors (small 's'). But except for the thrill of exploration, I don't see any other reasons to send rovers at present... *sigh*...

-the other Doug

[Phil Stooke]

I strongly agree with dvandorn that a series of small sample return missions would be very high priority right now.

Rovers are probably less useful on the Moon than on Mars, as the incessant impact gardening makes outcrops very rare. Nevertheless, there are some features that could be explored very effectively by rovers. My favourite is always Ina, or 'D-caldera'. The area around the Cobra Head could be another. Hyginus maybe a third. Lots of features within a short distance, ideal for a rover with good composition instruments like APXS, maybe a microscopic color imager, etc. A six month mission which collected samples from many documented sites and then delivered them to an Orion lander would be good too. I do agree with others that MER heritage is unlikely to be useful.

Phil

[tedstryk]

Honestly, as much as I would *really* love to see some robotic lunar exploration in the pipeline, I don't think that robotic rovers are the best investment for what we need from the Moon at this point, scientifically.

I agree and disagree. I think rovers are the best investment for robotic lunar exploration, specifically rovers which have a return stage or collect samples along the way to feed to a return stage. It seems to combine the best of both worlds.

[JRehling]

I agree and disagree. I think rovers are the best investment for robotic lunar exploration, specifically rovers which have a return stage or collect samples along the way to feed to a return stage. It seems to combine the best of both worlds.

...literally.

[RNeuhaus]

Thinking to send a rover to Moon. I only see a purposefull thing: collect more Moon material to Earth at lower cost is to send a rover to Moon along with the lander which later will bring the collected material to Earth. You can find more details about the next Moon missions by visiting at http://www.lpi.usra.edu/lunar_resources/documents.shtml

About the re-utilization of MER design for Moon:

Let us see about its design:

1. MER is good for cool weather between 25 - Minus 90 Celius centigrades. The Moon temperature has very large temperature swings between 120 - -130 Celius centigrated.
2. Batteries can only withstand for one Martian night versus 14 1/2 Selene nights. Of course, Lunar rover will need more heaters than MER due to the lower night temperature. MER is not well suited fo hot weather since it has no radiators or refrigerators to cool off the temperature
3. The EDL design for Mars includes (heat shield and parachutes) and the Moon ones will need more rockets.
4. Moon is as dusty as Mars but it has no winds so the MER must have some kind of adjusted design to puff any dust off from solar panels if it is used.
5. Long Moon night, the battery won't withstand and maybe it is more convenient to have a nuclear propulsion if the rover is going to withstand many Moon's nights.
6. The gears for wheels must be adjusted properly according to the lower gravity.
7. The Moon rover will need excavators in order to improve the excavation depth and also more effective than the MER's wheels.
8. Much more, it will need a new project to analyze which will stay, which will be changed, which will be improved and which will be removed. This might take 2-3 years of project.

Rodolfo

[Stephen]

I tend to agree with Doug here. While a MER type rover with minimal changes _could_ probably operate on the Moon a lot of the Rover's systems would be redundant or seriously underutilized.

More importantly the entire delivery system would need to be totally overhauled which in turn would change the design constraints on the vehicle. That alone would probably make delivering a "MER" to the moon a relatively inefficient and expensive exercise.

Does anyone have a back of the envelope mass budget estimate for landing material on the Moon? Roughly what sort of launcher do we need to get a few hundred kg softly onto the lunar surface? And once there how expensive is the remote comms likely to be?

And finally even if this was a relatively simple and cheap thing to do would this be a smart way to spend money?

I have no "back of the envelope mass budget estimate" as such, but back in the mid-60s NASA landed half a dozen Surveyors on the lunar surface. The last and heaviest was Surveyor 7, which weighed in at 305.7 kg (minus fuel), which is more than the MER rovers (185 kg) but less than a MER rover + MER lander (185 kg + 348 kg). (These MER figures, BTW, are from this Wikipedia page.)

However, according to the NSSDC page on the mission at launch Surveyor 7 weighed in at 1039 kg. That's roughly comparable to the MERs' 1063 kg. Of course most of the difference (between that and the 305.7 kg) would probably have been fuel! (Whereas the MERs only had 50 kg of fuel.)

According to the NSSDC page Surveyor 7 was launched on an Atlas-Centaur.

=======
Stephen

[Phil Stooke]

The Surveyors descended most of the way to the surface braked by a rocket engine underneath the frame. In the final stage of descent the engine and its associated equipment were dropped and the spacecraft continued its descent balanced on three small "vernier" thrusters. The descent stage fell nearby. None of the landers imaged their descent stages, but they might possibly be seen by LRO. Anyway, that accounts for quite a lot of the weight difference.

Phil

[AndyG]

Does anyone have a back of the envelope mass budget estimate for landing material on the Moon? Roughly what sort of launcher do we need to get a few hundred kg softly onto the lunar surface? And once there how expensive is the remote comms likely to be?

My back of an envelope. Assumptions first:

- LEO is obtained by off-the-shelf launchers (= cheap)
- All fuels are hypergolics with an ISP ~310 (= reliable, storable, cheap, old technology)
- Stage 1 does both the TLI and LOI burns, for a total delta-v of 3.9 km/s.
- Stage 1's dry mass is equal to the fuelled mass of Stage 2.
- Stage 2 is a lander from LLO to the lunar surface, capable of delta-v 2.2 km/s.
- Stage 2 has a dry mass of which 20% is the payload.

Regarding this thread on current boosters and their capabilities for LEO, you can land 1 MER as payload on the Moon, drawing on the above assumptions, using a Zenit 2. Titan III gets you 200kg of payload on the Moon. Proton, Delta IV Heavy and Titan IV are around the 290kg mark. The Atlas V HL tops the list at 336kg.

Going down the scale, a Soyuz gets 98 kg safely down, and the humble Pagasus XL could (aye, right!) land 5.7 kg of useful payload on the Moon. 5.7kg?? = "Half a Sojourner"

Not wishing to hijack the thread, I'd be keen to have input on the above assumptions...

Andy

[dvandorn]

The Surveyors descended most of the way to the surface braked by a rocket engine underneath the frame. In the final stage of descent the engine and its associated equipment were dropped and the spacecraft continued its descent balanced on three small "vernier" thrusters. The descent stage fell nearby. None of the landers imaged their descent stages, but they might possibly be seen by LRO. Anyway, that accounts for quite a lot of the weight difference.

Phil

You also have to remember that the Surveyors used a solid-fuel rocket engine as the main braking engine. I'm not sure, but I'd bet that there are higher-performance fuels out there that would give you more Isp for the weight than the solid fuel they used. (IIRC, they used the solid motors because it was far easier, and more mass-effective, to simply drop the motor and its casing out of the Surveyor structure after it burned out than it would have been to build tanks, piping, valves, etc., to feed liquid fuels into a braking rocket.)

The motor, again IIRC, was only abotut the size of a basketball (albeit with a nozzle attached). I have something of a hard time believing that this engine was more than 500 kg in weight -- they must have used quite a bit of fuel to power the final-stage descent thrusters, which were completely useless in terms of doing the major braking. So, I guess the solid fuel system did end up saving enough weight to make the landings possible...

-the other Doug

[mcaplinger]

The motor, again IIRC, was only abotut the size of a basketball (albeit with a nozzle attached).

The smallest current version of the Surveyor solid motor, the Star-37, has a mass of about 800 kg. It's about a meter in diameter.
See http://www.spaceandtech.com/spacedata/moto...r37_specs.shtml

[Phil Stooke]

I thought, from the pictures I'd seen, that it was more like a meter across.

Phil

[Jim from NSF.com]

Those versions of the Star-37 are longer and heavier than the one that flew on Surveyor