OpenLuna talk:Community Portal
An all-important aspect of any mission to the Moon is payload mass. It is not clear to this new member here what kind of payload mass is being considerd for the project or whether this is still an open topic. I will assume it is an open topic until I here otherwise.
I have always ascribed to the 'smaller is better' philosophy. In this context it leads me to ask: What is the smallest payload we could reasonably contemplate for a manned vehicle to the lunar surface? I don't know that there is a single 'right' answer to this but there are certainly some answers that are better than others.
A minimum manned lunar mission would be a single astronaut weighing, say, 100 kilograms. His food, water and oxygen for the round trip will be 10 kilograms per day, or about 100 kilograms total for five days out and five days back. This astronaut will need a spacesuit able to protect him from space conditions. This can be as little as 20 kilograms if we assume he only needs a pressure suit with thermal control and oxygen supply. For actually working on the Moon, however, the astronaut will need better thermal management, longer life-support capability and portable communications capability plus power to maintain all this. A strategy of pre-delivering lunar elements of a space suit and relying on the lightweight flight suit would keep the mass to the 20 kilograms noted above.
To this point we have 220 kilograms for payload.
Structure to protect the astronaut during flight and heat shielding to enable Earth re-entry would come to about 1,500 kilograms. Internal systems equipment for communications, navigation and life support are going to be around 100 kilograms.
So now we are at 1820 kilograms, or about 30% more than the Mercury spacecraft used in the '60's weighed. Landing gera, tank structure and landing engines would round out the mass to about two metric tionnes even, or about 4400 pounds.
Just a note, We are considering even less weight, and some items are much lower. For example, we are looking at a lunar lander in the 35 kilo range, and an inflatable heat shield of project moos type landing, in the 20 kilo range.
Very good questions, Please continue. --Paul 18:29, 25 September 2008 (UTC)
All topics are open, hence the name of the website! :)
Well, yes and no. do we need to land the food, water, air that we used on the trip out ? That saves 50 Kg right there. (don't get me started on margins) But that makes the landed payload mass at 170 kg, or if you pre-deliver, maybe only the 120kg. (I don't like this plan, but it deserves mentioning)
Looking at structure is really wide open to debate. How much does an aircraft weigh compared to it's payload. Consider a skydiving pack (15kg) which includes 2 'aircraft' for a 100kg person.
In Apollo, most navigation was done from earth. Attitude determination was done an on-board inertial platform and updated by astronaut star sightings.
The heat shield debate is a good point. The Lunar orbit Rendezvous mission was selected for Apollo to keep all this in lunar orbit and not land it on the moon. The Moose program was trying to make it incredibly light.
Until we finish hard designs with testing, it is really hard to say anything, let alone defend it. Current lander design is 140kg payload with 25kg of empty structure.
The big problem with this kind of mass breakdown is that the propellant is a huge factor. Basically, every time you do something, land, takeoff, go to the moon, enter orbit, etc you double the mass of the vehicle to include the propellants.
One Idea we have discussed is to use a restartable descent engine for all propulsion maneuvers and drop appropriately sized tanks as they are expended. This keeps the unused engines to a minimum (dead mass) and also only takes along the tankage that is full at any time. For a return flight, you weigh less and the acceleration off the moon could get pretty high, but it only starts at 1/6 gee, so high might be much less than a normal flight from earth.
Nothing saves, like saving weight.
so goes some of our thoughts.... -Gary