Post edited 12:38 am – November 29, 2009 by Rocket-To-The-Moon
Here is what I've been working on this afternoon. Just another concept.
The "shuttle" is the section below the CM, it is the source of propulsion for the CM. It is based on the Lunar Lander's engine and tank arrangement so that we can keep everything as common as possible.
To be honest, I am somewhat concerned that there will not be enough volume in the CM for everything. Maybe we need to think about having a two segment CM that is taller and skinnier. Just prior to reentry into Earth's atmosphere the top half would be jettisoned. I guess I'll need to make a new render to show what I'm talking about. (See below for my solution).
Videos are on their way, stay tuned.
Okay, this last image is my proposed solution to not being able to fit everything inside the CM itself. The upper section houses all of the ancillary equipment that would otherwise be stored in the SM (in an Apollo style system). This would also make it easier to pass fluids and gasses since we don't have to worry about going through the heat shield. Another benifit is that it helps to bring the center of gravity more toward the geometrical center of the vehicle which will make RCS easier. Prior to reentry the top part (I'm calling it the "Life Support Unit" for now) is jettisoned which exposes the parachutes.
I think that we might also be starting to get a sense of the scale of the booster. As shown here the booster is just shy of 28 meters tall but I think that it will be slightly larger in the end. The lander design's outside diameter is a little bit larger than the CM (ie, the lander won't fit on this rocket without a flared aeroshell) so we have a few options.
Make the CM and booster larger in diameter so that the lander, CM, and booster all have the same diameter.
Leave the CM and booster the diameter they are and use a flared aeroshell to fit the lander
Make the booster larger in diameter so that the lander fits without a flared aeroshell and then the CM is a smaller diameter than the booster
The third option is the one that is depicted in the bottom two renders of this post.
I'll do a quick render of the lander inside an aeroshell.
Okay, this render shows the lander on top of a Selene 3 that is the same diameter as the pictures above. You can see that there is a size problem here.
Do we:
Make the rocket larger?
Gives us more lift capacity which is good for commercial launches
Leave it as it is?
My next render will be a larger diameter Selene 3 with a squeeze adapter for the command module.
Okay, these next two renders show identical Selene 3 boosters with the two payloads. I'm starting to really like the looks of this. It is a big machine, but I don't think we can go too much smaller.
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2:50 pm November 28, 2009
Rocket-To-The-Moon
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4:26 pm November 28, 2009
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Post edited 12:41 am – November 29, 2009 by Rocket-To-The-Moon
I know that the rocket looks intimidating, but when you break it down into individual components it really isn't all that bad. The entire boosters is made up of 18 identical modular rockets so once we have one designed all we need to do is build more.
Here is our most basic manned rocket, the Selene 1 with a CM. Based on the evolution of the design (as seen above in this thread) the outside diameter of the modular booster is ~115cm and it is ~1015cm tall (nozzle to top of booster). In this configuration the Command Module does not have the "shuttle" attached to the bottom since it will be incapable of reaching orbit. The Life Support Unit could also be a smaller version (like is seen at the top of the first post).
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4:57 pm November 28, 2009
Rocket-To-The-Moon
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Post edited 11:13 pm – November 28, 2009 by Rocket-To-The-Moon
Here is the rocket family. I have excluded the Selene 2 from this render.
The Lunar Lander is on the far right side of the frame. It will be launched on an unmanned trip to lunar orbit via a low energy transfer orbit.
The large booster next to the lander is a Selene 3 configured with a Lunar Lander. This rocket will launch the Lander on a low energy transfer orbit to the moon. The trip to the moon will take approximately 5 months.
The next large booster is a Selene 3 with the Command Module. This rocket will take one astronaut directly to Lunar orbit where he/she will rendezvous with the lunar lander which was launched 5 months prior.
The booster on the left is a Selene 1 with a Command Module. This is the configuration that we will be using to test hardware for manned missions. It will be capable of suborbital flights. Once it is determined to be safe it will be used to launch paying passengers on suborbital joyrides. Profits will be used to fund CSTART.
The Selene 2 is similar to the Selene 1 except it is a two stage rocket (two stacked modular rockets).
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5:50 pm November 28, 2009
Rocket-To-The-Moon
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Post edited 11:54 pm – November 28, 2009 by Rocket-To-The-Moon
More videos:
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7:11 pm November 28, 2009
Rocket-To-The-Moon
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I've added a window to the Command Module.
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7:40 pm November 28, 2009
Luke Maurits
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Excellent work with the Sketchup renders, as always! They look fantastic and will do a lot to inspire people. Specific comments:
I like the "new" CM. The extended cylindrical nose is obviously a good approach, as it was used on Mercury and Gemini. I am not even sure it would need ejection before reentry – both those spacecraft kept the parachutes inside the cylindrical nose, which makes sense. Also, note that Mercury had an aerodynamic flap on the end of its cylindrical nose (called a "spoiler") which was apparently sufficient to flip the module around during reentry if it started coming in "backward". This sounds like a nice and simple approach to reentry conrol.
Perhaps the cylindrical nose looks a little too long to me, but it's probably to early to be making complaints like that until we have planned what goes where. If we want to make it shorter without sacrificing space, we could always make the angle of the CM cone less steep, making the CM a little higher. The astronaut isn't going to complain about extra space in there!
I am a little wary of getting a sense of size for the boosters based purely on these sorts of images. So far we have decided very little about what will be going in the rockets (but I really want us to start!). It may be the case that the actual rocket science of the boosters has something to say also about optimal sizing.
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7:45 pm November 28, 2009
Rocket-To-The-Moon
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Luke Maurits said:
I am a little wary of getting a sense of size for the boosters based purely on these sorts of images. So far we have decided very little about what will be going in the rockets (but I really want us to start!). It may be the case that the actual rocket science of the boosters has something to say also about optimal sizing.
This is definitely beyond my (limited) knowledge.
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8:32 pm November 28, 2009
Luke Maurits
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Another thought: The "shuttle" component of the CM should probably not be completely exposed. I'm not sure if you were simply modelling it that way for clarity's sake, but in the real deal I think a simple enclosing cylinder (open at the end, obviously) would be a good idea, to protect the fuel tanks from micrometeoroid impact.
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10:44 am November 29, 2009
Rocket-To-The-Moon
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Post edited 4:45 pm – November 29, 2009 by Rocket-To-The-Moon
I had planned for it to be out in the open to reduce mass, but I guess this is something that requires consideration.
Here is an extremely good overview of the implications of micrometeoroids.
The lander may require additional shielding since it will be in space for much longer.
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9:29 pm November 29, 2009
Luke Maurits
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I must confess to being confused by your rendering with the window. Which part of the window is the transparent part?
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9:38 pm November 29, 2009
Rocket-To-The-Moon
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The part that is parallel to the ground.
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10:17 pm November 29, 2009
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Post edited 4:32 am – November 30, 2009 by Luke Maurits
I don't quite understand how it works, then. The astronaut is lying perpendicular to the long cylindircal nose, facing upward, right? How can they see out of that window? Is there a mirror or something? Even if there is a mirror, why would we want a view facing backward rather than forward? Won't the angle of the CM's conical section lead to much of the view out that window being obscured?
What was your reason for going with the "bulge" shape instead of a simple flat window directly infront of the astronaut's face? The kind of thing you can see in this cut-away view of Mercury (which I love, by the way, I picture our module basically being a scaled up version of it).
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7:19 am November 30, 2009
Rocket-To-The-Moon
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Post edited 1:24 pm – November 30, 2009 by Rocket-To-The-Moon
Luke Maurits said:
I don't quite understand how it works, then. The astronaut is lying perpendicular to the long cylindircal nose, facing upward, right? How can they see out of that window? Is there a mirror or something? Even if there is a mirror, why would we want a view facing backward rather than forward? Won't the angle of the CM's conical section lead to much of the view out that window being obscured?
What was your reason for going with the "bulge" shape instead of a simple flat window directly infront of the astronaut's face? The kind of thing you can see in this cut-away view of Mercury (which I love, by the way, I picture our module basically being a scaled up version of it).
I think that the 2d picture may be confusing you. When on the launch pad the window is facing directly forward and the astronaut is laying on their back with their face behind (below) the window. Here is a video to help you visualize it. I'm also curious why you think that ours needs to be scaled up (compared to Mercury)? My main concern is that it is big enough so that the astronaut can don the moon suit.
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9:30 am November 30, 2009
Luke Maurits
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Aah, that video helps a lot, thanks. I completely misinterpreted the window's 3D shape. My bad.
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9:50 am November 30, 2009
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Post edited 3:51 pm – November 30, 2009 by Luke Maurits
Rocket-To-The-Moon said:
I'm also curious why you think that ours needs to be scaled up (compared to Mercury)? My main concern is that it is big enough so that the astronaut can don the moon suit.
Mercury was really small. Wikipedia says: "Because of their small size it was said that the Mercury spacecraft were worn, not ridden. With 1.7 cubic meters of habitable volume, the spacecraft was just large enough for the single crew member".
I think some scale up will be needed, mainly because we will need to fit more stuff in than Mercury did and our astronaut will need more mobility. The longest Mercury flight was 1 day, 10 hours, and the earliest ones were less than an hour. We will need to store a lot more oxygen, food, water, etc. than those flights would have needed for our mission which will be at least 6 days long as possibly longer. I doubt it could all fit into something Mercury sized. Also, given the short average flight time, I assume the toilet solution for Mercury was "just hold it in". We will need a better solution which will require a bit of mobility on behalf of the astronaut, more than you could get in Mercury, where you just stayed strapped in the whole time. Mercury didn't support any EVA options, so the hatch could afford to be smaller and getting into/out of the capsule could be more of a struggle. To be able to get into and out of our capsule during EVA easily and safely we will probably need a bigger hatch and more spare room. And, like you mentioned, there is the need for enough room to be able to put on the moon suit.
Don't worry, I'm not talking about scaling it up much. I think our module will have to be larger than Mercury but would probably be smaller than Gemini (which is basically just Mercury scaled up enough for a second seat, with some stuff shifted into a "service module" at the back). It would definitely be Gemini-sized in the worst case – never larger.
Slightly unrelated, but I've also found a nice diagram of the insides of Gemini. If you imagine removing the second seat, there is a lot of spare room, it should be enough to fit all of our supplies – although I'm a little bit nervous about oxygen. Has anyone done the maths on not just how much O2 we would need but how much space it would take up if stored at a realistic pressure? Maybe we will need a service module approach for this after all.
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1:06 pm November 30, 2009
Rocket-To-The-Moon
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Post edited 7:08 pm – November 30, 2009 by Rocket-To-The-Moon
On the topic of Oxygen:
My thoughts were that we would have ultra high pressure oxygen cylinders (~10,000psi (second link) is about as high as I could find) in the "nose" of the module. The pure O2 would be fed into the life support mixer that controls the flow of pure oxygen and recycled air (CO2 scrubbed air). Prior to reentry the nose would be jettisoned (reducing the mass of the reentry vehicle and thus reducing the thickness of the heat shield, but also increasing the peak acceleration…which we would have to keep an eye on). Prior to the separation the cabin air would be enriched with oxygen so that the scrubber can keep a habitable atmosphere until the capsule is recovered.
In order to determine how much oxygen we need I guess that we need to determine how much oxygen a person uses in 1 day.
I found a web site which stated that an average adult each day consumes 4 lb of food, 2 lb of water, and 6 lb of oxygen. I could not find a corroborating site, but the numbers seem roughly reasonable. Assuming 6 lb of oxygen per day is right, how large a room do you have to seal? Incidentally, an exercising adult uses oxygen at about 15 times this rate, so remain calm!
6 lb is about 2.73 kg. Since a mole of oxygen has a mass of 32 gm = 0.032 kg, an adult needs about 85 moles per day. Since a mole under standard conditions (atmospheric pressure, 300 C) occupies 22.4 liters, 85 moles occupies about 1900 liters or 1.9 m^3. But air is 21% oxygen, so about 9.1 m^3 of 321 ft^3of air is required for one adult for one day.
So according to this we would need ~1900 liters per day of pure oxygen (at standard atmospheric pressure). Assuming that we use a 690 bar tank (10,000psi) we could squeeze that 1900 liters down to 2.75 liters (did I get that correct?…ideal gas law pV=nRT) per day. Multiplying this by a 10-12 day mission duration comes out to about 27.5-33 liters of pure oxygen @ 690 bar starting pressure. For those who have trouble visualizing things in metric units (myself included), this comes out to a tiny 1.165 ft^3 for 12 days of oxygen. Of course we need some sort of re breather system to scrub CO2 from the cabin.
What kind of atmosphere do we want? The ISS uses a composition similar to air. Do we dare forget Apollo 1 and go with a pure oxygen cabin? The real issue with Apollo 1 is that they had pure oxygen at sea level which meant that the absolute pressure was atmospheric plus the overpressure. Is pure oxygen safe if we only use .7atm while in space (532 mmHg)?
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1:30 pm November 30, 2009
brmj
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Post edited 10:55 pm – November 30, 2009 by brmj
"Is pure oxygen safe if we only use .7atm while in space (532 mmHg)?"
Safer, I suppose, but it's still dangerous. I'm against it. We really wouldn't need all that big a tank of Nitrogen, for example, to contain several habitable volumes worth of the stuff. We'd want to have a few extra, though, in case unschedualed EVAs are required for some emergency or there is a leak or something, but it should still be reasonable.
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4:32 pm November 30, 2009
Rocket-To-The-Moon
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Good point. The nitrogen will just serve as a space filler to reduce the partial pressure of the O2. And you are correct in stating that it would only need to be replenished after we dump the cabin pressure.
This is sort of outside the scope of this thread, but at one point we talked about pumping the cabin air into a storage vessel prior to EVAs. This would probably be relatively easy to do and (nearly) the entire volume could fit into a fairly small low pressure tank (standard 450psi 31bar oxygen bottle). Upon repressurization one would simply vent the bottle's contents into the cabin. Then fine tune the mixture with nitrogen and/or oxygen until it reaches the desired pressure/mixture.
The weight of the pump/storage bottle might not be worth the effort though.
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11:29 pm November 30, 2009
Luke Maurits
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I am pretty strongly opposed to the use of pure oxygen, it just doesn't seem worth the risk, even if we can reduce that risk compared to Apollo 1. If something did go wrong, we would look like idiots (and probably feel like worse) for overlooking one of the best known space safety issues, which was learned so early in manned space flight at such a high price.
My thoughts were that we would have ultra high pressure oxygen cylinders (~10,000psi (second link) is about as high as I could find) in the "nose" of the module.
I wonder about how much room we will have/need in the nose. I suppose we can make it arbitrarily long if we need to, but in addition to it looking a bit silly I am sure that keeping it shorter will have positive aerodynamic effects and I worry about vibration with a relatively long, thin part of the craft sticking out from the opposite end of the booster.
I assume that a lot of the nose will be taken up by parachute / paraglider stowage. This seems to be the case in Mercury and Gemini, I assume that parachutes haven't miniaturised since those days since the entire operating principle depends on surface area. I also really like the way Gemini's RCS is localised entirely to a block at the base of the nose (whereas Mercury has jets at the base of the cone and the fuel storage behind the astronaut's back, necessitating a lot of plumbing) and figure we should emulate that too. This may not leave much room in the nose for gas storage.
I was thinking about long, cylindrical oxygen tanks, parallel to the nose, being stored in the space under the seat. Here is a terrible concept diagram:
I suppose it will be hard to start planning this kind of stuff in detail without some sort of CAD solution where we can specify sizes for things and see what actually fits where.
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