New Mars Forums

All this verbiage to describe missions is confusing. 

Maybe it could be clarified by using a format something like the following?  (Example is very simple and one-way, numbers are bogus.  More complex examples would leave mass/equipment behind for subsequent phases.)

================================================================
Mission: TotallyDirectToMar
================================================================
LOCATION                       Mass        Consisting of these components
-------------------------------------------------------------------------------------------------------------------
Mass@Earth                    800MT     1 heavy lift launcher, fuel, Mars transit vehicle fueled, etc etc
Mass@Mars Atm Entry     0
Mass@Mars sub-sonic      0
Mass@Mars Surface         0
-------------------------------
** Launch direct from Earth's surface to Mars atmosphere entry, and <brief notes justifying/explaining the transition to next phase>
-------------------------------
Mass@Earth                    0     
Mass@Mars Atm Entry     40MT          30MT fueled Lander, 10MT Aeroshield
Mass@Mars sub-sonic      0
Mass@Mars Surface         0
-------------------------------
** Aerocapture to sub-sonic and <notes explaining why that should work>
-------------------------------
Mass@Earth                    0     
Mass@Mars Atm Entry      0           
Mass@Mars sub-sonic       30MT           fueled lander, etc
Mass@Mars Surface          0
-------------------------------
** Rocket landing and <why the fuel expended makes sense>
-------------------------------
Mass@Earth                    0     
Mass@Mars Atm Entry      0           
Mass@Mars sub-sonic       0
Mass@Mars Surface          8MT             Lander, 3 crew, supplies, whatever
-------------------------------

Yeah, it's a bit bulky, but it'd make it easier to compare mission profiles, especially when you're trying to explain what you think is wrong with someone else' scheme.
For crewed mission profiles, assume a pre-positioned hab with supplies, small nuke plant and small ISPP plant (rover fuel if nothing else).

I didn't find their argument conclusive. 

The extra dV to Phobos is significant, I agree - though they could go do Deimos first, study it a bit, then go on to Phobos - much increased value for not much extra dV.

The slight increase in Mars surface coverage isn't terribly significant - and if it were, putting up a small relay sat could give you fuller surface coverage.

Near continuous solar power is nice - but losing only about 3 hours of sunlight a day on Phobos doesn't seem like that big a deal - charge some batteries when everyone is sleeping - you'll need them anyhow to handle varying loads.

The increased lag to Deimos won't be a big deal for the level of robots we'll have by their proposed mission date.  But it does make remote telepresence far less convincing,  I suspect a humanoid telepresence robot wandering around on Mars giving crew members much of the feeling of "being there" would make a near-Mars mission far more popular on Earth.  And being in a lower orbit also makes a telescope aimed at Mars that much more useful - e.g. for weather and season studies.

The longer duration exposure to one Mars site doesn't seem like a big deal - two 3 hour shifts working two sites on opposite sides of Mars is probably about right before turning over to the next crew shift.

And of course, the big bonus would lie in exploring Phobos itself - far more interesting than Deimos.  You're going all that way and landing on one of two moons - and you pick Deimos mainly because "the light is better there"?  Sounds like the punchline of an old joke...

I keep seeing quotes (E.g. Wikipedia, but other sources also) that Phobos' L1 point is 2.5km over Stickney crater. 
But shouldn't L1 be directly between the moon and Mars?
And Stickney is on the "Western" limb of Phobos as seen from Mars, right?
Could it be that they are actually thinking about L4 ? 
Or am I missing some aspect of the orbital mechanics involved?

Given how small Phobos is, seems like staying in orbit at L1 would make sense, where you could spin for gravity while still getting most of the radiation shielding of Phobos and Mars.  Or maybe a solar synchronous orbit, since that seems to be the major concern in the UT proposal.  Can't take advantage of piled up regolith for more shielding that way, of course.  But the crew will want to get out and explore Phobos' surface anyhow, and getting to the surface is extremely easy - so perhaps the crew could split their time between surface and orbital bases, with most of the high power-consuming equipment staying in orbit?

An interesting article on auto-rotation as an alternative for Mars landing. 
It seems to focus on fairly small payloads, however.

Your later post is correct, this is getting off topic.  But please allow me to add some data to my previous post to explain, since it is key to the question of HOW to land things, and you are still objecting to the feasibility of the "multiple smaller deliveries and assemble" approach.

I took 25mT of mass from Zubrin's hab sketch, and assumed a design based on  twenty five modular, folding, 1mT shipments of maybe 250 components, well designed for ease of assembly (e.g. all connectors built in - very few separate nuts and bolts).

200 sq-m steel building construction kits with a LOT more components and manually added nuts and bolts, take about 1.2 man-hr per sq meter to build on Earth, where components weigh at least 2.5x more. 

So figure about 2 man-hr per sq-m on Mars, not counting tele-operated robotic assistance that does any heavy lifting.
A hab 8m across -~50sq-m - should take around 100 man-hr, or about 9 days for a crew of two. 

So, having estimated this from several angles now (kit buildings on Earth, EVA construction of ISS), 2 weeks seems like a reasonably good ball-park estimate for the structure and basic air and power supply.   A week or maybe two more to finish the interior and robotically bury it for shielding.

Splitting the crew might multiply the chance of losing one crew member - but greatly reduces the chance of losing the full mission.

Assume equal 5% chance of a fatal crash for a 4 person lander versus each of four 1 person landers.  Chance of killing all 4 crew is 5% for 4 person, but only 0.000625% for 4 separate landers.  Of course, the chance of ANY crew dying is 5% for 4 person, versus about 18.5% for 4 separate landers.

So which would you rather have - a 5% chance of all 4 crew dying, or a ~20% chance that 3 crew will have to carry on after one dies? 

I'd be willing to bet that if all 4 died, it'd be at least a decade delay, if ever we went back.  If one died?  Global mourning and pride in the bravery of the other 3, and "we must carry on to show his sacrifice was not in vain" - while in the background engineers scramble to fix the specific problem revealed, so the next landers each have only a 3% chance of a fatal crash.

And that's before considering that a one person lander MIGHT be safer, if you make the heat shield the same radius as the four person lander, since it should get far more aerobraking value, and so have more fuel reserve for control and landing.  You'd end up putting more total mass into human landers, but split 4 ways each lander will have more margin for error.

Regarding the hab:  I don't think it does need to be monolithic.  If you send it down in parts and teleoperate robots from Phobos to assemble and test it, you've gotten away from that requirement. 

Even better, just send down structural supports and long skinny air-tight sandbags for the robots to fill and weave between inner and outer structural supports and cement together before burying the whole thing.  Early Martians could live in "log cabins", like earlier pioneers. 

@Glandu - thanks for the link.  Yes that goes in the direction I indiated - except I'm thinking to take it even further  for the human landers - land ONE human at a time, not two.

@Rune and others - with Internet Explorer 9, right clicking on the link brings up Translate with Bing. (Google has an equivalent.)  Very readable translation for the most part.

@GW - I'm a little frustrated - you don't seem to be catching the essence of my proposal, namely:  Use a rocket NOT in-line-of-flight to slow down, and NOT to get lower faster - but rather aimed at the surface, to SLOW the rate of descent - to maximize the net benefits of aerobraking.  When the value of aerobraking falls below the value of rocket braking at the same thrust level being used to slow your descent, switch over to rocket braking.   So long as aerobraking is yielding more deceleration than the rocket thrust needed to stay aloft longer, it's a net win.

Actually, I've been wondering if we haven't gotten so caught up in landing decent-sized habs for long-duration missions, and multi-person human landers, that we aren't missing another "back in the box" approach.  I.e. send down much smaller packages using simpler methods, and rely much more on building and putting things together on the surface.   (This fits in with the idea of staying in orbit for a while and using tele-robotics to set things up, before descending.)

Most of the mass of a mission would be dropped as modest quantities of raw materials in simple but useful form, and would descend using only aerobraking and parachutes, and airbags for things you care about damaging.  The idea being to provide raw materials in easy to use forms, instead of finished products, as much as possible.  Think more like "empty sandbags" than "hab wall plates".  Inflatables and patches, not metal sheets.  Slabs of plastic to melt and extrude for pipes. Etc.

Humans would land individually in small "landing frames" - focusing all mass on getting them down safely and on target.   It'd be unpressurized, with the human explorer in a pressure suit and carrying some survival gear in case the craft lands off course and needs to be retrieved.  It might well follow Luis' approach of killing most orbital velocity using rockets, then descending sub-sonic with parachutes and using canted rockets for a soft landing.  Or it could rely on aerobraking in a shell, followed by parachute and rockets - riskier but cheaper.  Maybe a mix - rockets for humans and test landings before sending down humans, aerobraking otherwise.

As small landing frames would be cheaper per unit, a dozen could be tested by landing other important and somewhat fragile equipment, before the first human goes down.  If one does fail with a person on board, you don't lose your entire crew - it's a tragedy but not a disaster for the mission (though if it's the first human to descend, it may mean a mission abort).   Once down, the landing frame becomes a resource to be disassembled - support struts become support beams for structures, cryoliquid storage tanks and electronics are put to use, etc.  Or take off the rockets and attach wheels to make a rover or tractor.

I don't think you quite got the difference of what I was proposing.   Musk and GW's plan has been to use rockets fired at an angle to slow the craft, while avoiding turbulence.   I presume their thought is to aerobrake AND use rockets to slow down quickly, then use rockets for the rest of the way down.  You could do that, but basically the sooner you slow down, the less deceleration due to drag, and the more you need to use rocket power to slow down.

What I proposed is to use rockets only to control descent, keeping the drag at a roughly constant level as long as possible - until it has slowed so much that drag force has become less than 0.4g, while not falling below some safe altitude - perhaps a kilometer up.   All the way up to that point, you will have been getting a net benefit from aerobraking, over the cost of using your rocket.  This approach maximizes the free deceleration of aerobraking.

As to slowing before entering the atmosphere - yes, of course you could - but again at the expense of relying much more on rocket power.  And more rocket power means more mass, more mass to be sent all the way from Earth  at higher cost in dollars, or higher cost to other stuff you could otherwise have brought.

Speaking Tours for returned Mars explorers.  Put them under contract before they go to Mars.  They get a living stipend and maybe a cut of the fees, with a requirement that they spend at least 2 years immediately after return "on the circuit" giving speeches and presentations and asking rich people for money.   With a rate schedule varying from perhaps $25000 to speak to a large auditorium full of school kids, to $1M for a buddy-buddy presentation with some self-promoting star or politician.  Plus they can ask for grants/funding for new missions.

Virtual speaking tours FROM Mars.  Use holographic projection recorded on Mars (may actually be 3D graphics from motion recording, for cost reasons.  Audience can record questions about an hour in advance of the Q&A session, and get "live" answers to validate to the audience that this isn't JUST a canned recording.  Part of this experience must be that the explorers see their audience - especially those who asked questions.   These might be big media events more like concerts.  (Heck, maybe send along a famous performer and let them perform concerts from Mars.)  Can also pair "live from Mars" presentations with a returned Mars explorer to give a better experience and extend the value of both live and virtual speeches.  E.g the live explorer talks while the audience waits for their recorded questions to be selected and sent to Mars and transmitted back to Earth along with the explorer's answers.  So the questioner gets the experience of their image having been sent to Mars and back as a bonus!

Figure an average of $200K per speech (including the cheap ones to school kids), average of 1 per day (some days with more than one, some days off).  Maybe could keep that going for 2 years - about $150M income.   Add sales of official Mars merchandize (T-shirts, hats, jackets, patches, flags, coins, spoons, etc) - overprice most of it with explanation that it all goes to support the Mars effort, and you could probably pull in $10M - $20M.

Personally signed prints of photos taken on Mars.   Signed books.

Might as well forget "Moon and Mars".

The Democratic president elected in 2008 will throw out Bush's "vision", slash NASA's budget, and order it to re-focus on a vision of "Earth Centric Space" or "Earth First" - monitoring global warming, etc.  If we're lucky, the popular robotic probes and space telescope programs won't be cut.

Then, perhaps as soon as 2009, a mass of papered-over problems will tumble upon us in a rapid, domino-like cascade.  The 2010's will likely be hell for the US and the world, and dreams of Mars will be set even further aside.

I think liquid AL as fuel would be simpler - no pre-mixing to get right.  It should be a bit safer - no chance that a spark or blow-back will ignite the fuel at an inappropriate time or place - e.g. during fuel mixing.  It might get a bit more thrust, since it starts out about 700 degrees hotter.   There'd be no requirement of getting the AL dust powder grains to a specific fine-ness in order to assure a clean fast burn.

So I guess I'd ask the question the other way around - why bother mixing LOX and AL powder?   It's not going to make a simpler rocket, I suspect - possibly more complex.  And I also suspect that any pumps or valves would get a lot of wear from AL in LOX flowing through - hurting potential re-useability.