New Mars Forums

I wouldn't call nuclear engines an existing technology - NERVA was a prototype but that was a few decades ago - long shelved and forgotten, and, if you recall both the Galileo and Cassini (and even New Horizons to a smaller degree), there's been continuing protest of nuclear material in space.

Plasma drive needs perhaps one more decade of refinement, including at least one Deep Space-style mission to test it, otherwise I'd say that qualifies.

No no no.

One lander is directly for the manned excursion but the second would be a cargo vehicle dedicated to delivering a base element.

I like your thinking, but I'm not certain.  The MRO and MGS would be barely a quarter the size of LSAM; when its something small its easier when its massive and bulky it tends to be difficult at best.  There'd be a huge amount of momentum/velocity.

I don't think there'd be enough fuel left in LSAM for even a partial orbital break, but possibly the CEV service module could do something there - if LSAM and CEV were still docked ala Apollo 13 on its return trajectory perhaps the service module could provide the burn.  No harm done since the whole assembly is en route to Earth's atmosphere anyway.

I think this may lead to a workable idea...

Ok, a single-stage LSAM would rendevous with the CEV as in the normal architecture - empty save for some maneuvering propellant, no ion drive no additional frills.  CEV would do escape maneuver, the whole assembly en route for Earth.  Nearing Earth CEV performs a final burn to slow velocity but still keeping target for atmospheric entry.  Service module jettisons burns up, CEV reenters and lands, but the LSAM would maneuver to graze the upper atmosphere.  It would likely take at least a month for it to reach a circular LEO, at which point a refueling pod can be launched (perhaps even a modified Progress is the Russians get in on this).  New CEV rendevouses, and the CaCLV sends up the escape stage.  New mission launched, lands, repeat cycle.

Given this aerobraking concept though I would recommend limiting LSAM down to 5, maybe 6 reuses.  This whole revised architecture would have to be saved when the CEV is upgraded - perhaps as a prerequisete to Martian flights.  Also this is for manned lunar flights - cargo would be set up via CaCLV only.

Keep in mind for it to be reuseable it needs to be refueled otherwise you're talking about either a one-time use lander or something like the Mars Direct lander that serves as a surface module.  I don't think a LSAM ascent stage can be reuseable like the CEV.

Limiting its reuse is a good idea too - perhaps on its final landing it could be left on the surface for, say, fuel storage.

Refueling isn't as big a deal as many people here seem to fret about.  The Russian Progress regularly refuels the ISS; it doesn't just perform burn maneuvers for the station - that's just a cost-saver feature done before the Progress is used up.

A single-stage LSAM isn't inconceiveable - a two-stage lander has its own complexities and downsides (it DOES require two engines, two seperate propulsion systems - I'm suprised people aren't ragging about that); the only difference between the two is that the two-stage has the benefit of already being tested via the old LEM.

Sure it will be heavier than just an ascent stage - keep in mind however when it lifts off it will be only loaded down with barely half the fuel it originally landed with - it simply needs enough to get it into lunar orbit and between it and the CEV there'd be sufficent rendevous fuel.

To me the only question is how to get the LSAM back to LEO for refueling.  Aerobraking is out of the question and as much as I support ion propulsion those solar panels would be too bulky.  Maybe an ion tug could bring it down to LEO.

Again to summarize an entire single-stage LSAM is feasable, but bringing it back for reuse is the question.

I think a reuseable LSAM might be a good idea but we would need to develop something like a single-stage LSAM.  I often wonder why the lunar descent engine can't simply be used twice.  The SSME isn't the only engine capable of restart; Lockeed and its Centaur upper stages and numerous other disposable rocket engines, including the J-2s from the old Saturns, were capable of stopping and then performing a second burn.  The only factor that may be considered is lift-off with the landing gear versus just the crew cabin (which the current ascent stage pretty much is).

If its a simplified single-stage craft it could be modified for refuel and reuse later on too.

Reuseability is a nice option but at our stage its obviously why the shuttle proved to be a nightmare - that and fact it was built on too many compromises.

Engine pods are out of the question.  The new 5-segment SRVs will be enough to tweak; if they can manage to reuse them that's more than enough for the CaLV and the CLV for that matter.  The CEV crew capsule could potentially be reused too, but beyond that reusability is too much of a headache when the main focus is just getting something up to the moon or beyond.

Do it in small, manageable bits.  I don't want to see another Challenger or Columbia bursting into flames because of too many compromises again. 

There are several things to consider when strolling about the moon...

1) Moondust is much like coal-dust: abrassive to machinery, space suits, and the air sacs of the lungs.  They are making developments in a kind of anti-static coating to prevent the dust from accumulating but I'd rather not be on the rover whose wheels jam when we're a hundred kilometers from base.

2) Walking, or even roving, on the moon is not strolling through the park.  Its more like strolling through Chernobyl, especially during a solar flare.  It will be some time before we develop a fully reliable 'space weather watch' system, and it will likely be even more sudden than a tornado watch here on Earth.

3) You have to carry your own air supply wherever you go.  On a pressurized rover this will be less of a concern since it will be prepared for the trip, but if it breaks down beyond walking range our lunanaughts are screwed until a rescue vehicle arrives...and with two launches a year to the moon its debatable if there'll even be a second rover to use.

There's no reason not to explore multiple regions of the moon, I never said we couldn't.  But we have good reason to be selective: human lives.  If a person dies on the moon it will be a sad day but more to the point people here on Earth will probably rally "We don't belong on the moon!" and then we'll be back where Apollo 17 left off and the shuttle began.

Use probes to scout a site first, they're at least good for that much.  Opportunity spotted literally craterfuls of water-rich minerals; now we know for certain where to send human geologists.  Use both man and machine, but remember that machines are the only one expendible of the two.

Only a red-herring if its a chemical propellant tug.  If its ion driven a few tons of xeon would last several years; if an oxygen-propellant ion drive is developed all the better - fuel exclusively from the moon.

You do have one point though: the "fuel" to go with the oxygen is all the moon lacks.  Mars can provide that in time or even Titan and the outer solar system in the distance future.  Using Lunar Oxygen just lowers the weight from Earth, as I'm sure you've heard from other LOX advocates.

However, I'm going to add this point: don't develop the LOX tug just yet.  Its putting the carriage before the horse; the horse in this case is the LOX production facility - in situ propellant production and all.  In a stripped-down space program tugs are indeed luxuries.  Their time will come when we have something self-sufficent started.  If we're worried about hauling cargo though through space radiation you can be sure people will be wanting unmanned tugs doing the job.

Don't depend on LOX to get to Mars, not initially - but it will come in handy if we intend to stay there.

I think this actually may be a good point, and idea.

One thing any government agency can be sure of is having barely half the funds it would like to have to work with.    Chosing two sites on the moon to start from and then expand out will help focus NASA's limited intelligence and capability.

Pick one site for resources (most likely in the South Pole region near both the alleged ice and the point of Eternal Light), but then pick the second site for scientific potential such as an ancient lunar volcanic vent.  Concentrating equiptment will allow a fully developed base to be created as opposed to a dozen abandoned lander stages with scattered cargo blocks.

First NASA will build the CEV, then the CLV, CaLV, and LSAM; once these first two agendas are built and operating the third agenda ought to be selecting a pair of sites for long-term habitation (whether a future colony or a simple Antarctic-analog facility).

Maybe it will limit science on the moon at first, but damn it just GETIING to the moon will be a camel-through-the-needle-of-an-eye effort as is.  May as well focus our work - probes can always be scattered across a planetary body to get a better samples - humans are another matter.

*pair of stranded astronauts on Mars eating their now-dismantled edible lander*

"Pass me another excursion module leg...."

"Oooh try the rover's right wheel.  They went with chocolate doughnut... "

  Somehow this is what went through my mind when this topic came up.

I think Ion engines could have applications toward manned exploration but only for the cargo-transport element of it.

Power sources will become less massive over time but given the actual thrust of an ion engine regardless no human being will wait in low orbit for several months straight especially when other systems can get them to the moon in a matter of days.

One more merit to terraforming-under-glass just a region of Mars:

As the Red-Green-Blue Mars trilogy time and time again brought up there will be those devoted for preserving the planet as hostile as it may be.

I'm not a fan of rock gardens myself but it might be wise on a scientific basis to preserve Mars for a while yet - it holds alot more of its ancient history intact than Earth while still accessible to human hands.

Also, just in case, if we find native life (most likely in some microbial form) this would allow it to be preserved while allowing humans their own refuge on an otherwise harsh Martian surface.