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5:28 am
January 8, 2010
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Luke Maurits
| | Adelaide, Australia | |
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I agree that the mass of the lunar module structure behind the fuel tanks (including the engine mount and engines) will probably exceed the mass of the structure we had the lander docking into in the original Bravo plan. However, I'd feel fairly okay wagering that it would not exceed it by more than the mass of the lander which we get to discard in this plan (and certainly not by more than the mass we would save on fuel because of that). I can't really do the numbers on this without a better idea of what these structures may weigh, but I suspect this configuration could be less massive overall. I guess I could make up a few figures to test this out.
Another thought on this matter: do you actually save money on a Falcon 9 launch if you lift, say 9,000 kg instead of 10,000 kg? Or is the price fixed? If your payload is less than the maximum do they add some ballast to bring it up to the maximum so that every launch has the same dynamics, or are the computers onboard able to compensate for changes in launch mass? If we're stuck paying $35 million regardless of mass we should not be afraid to add mass where it will reduce complexity (which I would argue it does in this case) or remove the amount of expensive/exotic material we have to use.
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Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.
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9:39 am
January 9, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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Here is a first render of what the stack may look like. I haven't included the engines yet.
 
Does this look like it is headed down the correct path?
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Main Workgroups: Propulsion & Spacecraft Engineering
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10:34 am
January 9, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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Post edited 4:44 pm – January 9, 2010 by Rocket-To-The-Moon
Here is a to-scale representation of what the stack would look like inside of the Falcon 9 fairing. As long as we don't exceed the maximum mass the stack can easily grow longer.
The next challenge for this render is trying to draw in the support structure. I'm not quite sure how to approach this problem.The lander's engine bell needs to be able to clear the fuel tanks so it isn't possible to just slide it directly sideways. It will be necessary to rotate it out in such a manner that there are no conflicts. I imagine that the stucture will be a fairly typical tubular aluminum construction.
Here is the size of the fairing.
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Main Workgroups: Propulsion & Spacecraft Engineering
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11:02 am
January 9, 2010
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Luke Maurits
| | Adelaide, Australia | |
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These new renders look seriously awesome, thanks for some great work.
A very minor nitpick: I feel like the nose should be cylindrical for some length before tapering to provide somewhere to store the RCS unit.
It's good to know our stack phyically fits in the Falcon 9 fairing – it hadn't even ocurred to me to consider that! Looks like we have room to spare.
I notice that in the most recent render, the large fuel tanks occupy a wider area that the base of the CM. I assume that the width of the lander relative to the CM diameter is the driving reason for this? We could accommodate this by having the extension module have a larger rear than front diameter (like the Gemini adaptions) if we need to, but I guess our scales aren't sufficiently well nailed down to know if this is necessary.
With regards to positioning the lander so that it can clear the fuel tanks – I apologise if this is a stupid question but couldn't it just sit a little further lower than it does in the current renders? This will add a little extra mass by making the lunar mission module a little longer, but it would probably be negligible compared to the total mass, and it would certainly make things easier.
The structures for the various modules should be pretty simple – an aluminium skin over a skeletal frame of titanium or the like. Can't wait to see these!
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Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.
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11:14 am
January 9, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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Post edited 12:05 am – January 10, 2010 by Rocket-To-The-Moon
Luke Maurits said:
I notice that in the most recent render, the large fuel tanks occupy a wider area that the base of the CM. I assume that the width of the lander relative to the CM diameter is the driving reason for this?
Yes, the lander has the largest radius from center and I made the tanks to just fit inside this radius. I originally did have the Gemini style adapter, but then realized that there is no need for this aeroshell (fairing) if the entire stack will be inside the Falcon's fairing.
As for the longer nose; I can easily put the longer nose back on the CM.
<< Note: Obsolete
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Main Workgroups: Propulsion & Spacecraft Engineering
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11:32 am
January 9, 2010
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Luke Maurits
| | Adelaide, Australia | |
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Rocket-To-The-Moon said:
Yes, the lander has the largest radius from center and I made the tanks to just fit inside this radius. I originally did have the Gemini style adapter, but then realized that there is no need for this aeroshell (fairing) if the entire stack will be inside the Falcon's fairing.
- The mission extension module will also be used on orbital flights which are too light to launch from the Falcon 9 and may be launched from our own modular hybrid booster, so it will need an aerodynamic shell anyway.
- Even in the lunar configuration where the Falcon 9 fairing provides aerodynamics during launch, there will still need to be some kind of shell over the stack to provide micrometeoroid protection, solar radiation shielding, etc.
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Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.
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11:40 am
January 9, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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Post edited 12:05 am – January 10, 2010 by Rocket-To-The-Moon
Good points.
The mission extension module is currently depicted as the four small spherical tanks directly under the heat shield. In this lunar configuration I haven't really paid the necessary attention to differentiating the extension module from the lunar mission module (does it have a specific name yet?).
For micrometeroid protection the render above is the shell that I tentatively made. (Edit: this is obsolete)
Here is the stack with the long nose. This design is large enough that a substantial amount of RCS propellant can be stored up there.
EDIT: I also tried to slide the lander out directly sideway and it will work.
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Main Workgroups: Propulsion & Spacecraft Engineering
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1:07 pm
January 9, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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Post edited 12:09 am – January 10, 2010 by Rocket-To-The-Moon
Here is the frame that I came up with:
This should be plenty strong for the gentle accelerations that the craft will experience in space. It will probably be necessary to have a support structure inside the fairing during launch, but I think that is fairly common in other spacecraft (it would only add several tens of kg launch mass).
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Main Workgroups: Propulsion & Spacecraft Engineering
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1:20 pm
January 9, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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Post edited 7:40 pm – January 9, 2010 by Rocket-To-The-Moon
Lander Extraction:
Return Configuration:
Atop a Falcon 9 Heavy.
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Main Workgroups: Propulsion & Spacecraft Engineering
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7:54 pm
January 9, 2010
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Luke Maurits
| | Adelaide, Australia | |
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Post edited 2:05 am – January 10, 2010 by Luke Maurits
More awesome work, thank you so much. A few points:
- I know you lengthened the nose at my request so I feel like I'm being demanding by saying anything further about it now, but I think that the current nose is considerably too long. The RCS for Gemini was entirely contained in the nose, including its propellant (this is where I got the idea for that), and the length of their RCS unit was quite small in comparison to ours. They probably used a higher Isp fuel than we will, true, but that spacecraft was also heavier. I think a nose section half as long as the current renders would be a more accurate representation of what we will need. Is this hard to change?
- The name "Lunar Mission Module" (LMM) has been made fairly official by virtue of its inclusion in the first draft of the CLLARE Project Overview document. I made this decision by myself purely because I needed something to call it, if people hate it or have better ideas I've no objection to changing it.
- I assume that the tapering of the end of the LMM is motivated by a desire to minimise its mass? Interesting idea, I can't think of any drawbacks to it.
- Maybe my main concern overall: I'm not sure that the interface between the Mission Extension Module (MEM) and Lunar Mission Module (LMM) is clearly modular enough. Remember that there will be missions flown which are just a CM with a MEM behind it and a small Retro Module (RM – for deorbit burns). This means that the MEM exists as a purely standalone piece of hardware – it's frame should consist of two rings with 4 members joining them. The end of the LMM will have its own frame ring, so at their interface there should be two rings? At first I thought that the fact that the MEM's supply tanks and the LMM's propellant tanks were so tightly nested was a problem for modularity too, but thinking about it, the LMM never has to interface with anything other than the MEM so it's not a problem for the LMM's tanks to protrude a little forward of the front of its frame to accommodate this tight packing. All of this, of course, is how things look from my perspective and how I had interpreted the modularity of our designs, which is not necessarily the way. EDIT: I just noticed you've already mentioned yourself that you haven't properly differentiated the two, sorry for not picking up on this bit originally – too distracted by the pretty pictures!
- Is the Falcon 9 heavy man rated as well as the base Falcon 9? Personally I suspect a Falcon 9 will have more than enough lifting capacity for us but it would be good to know anyway.
- In light of our recent official partnership with One Flag In Space it would be nice to start trying to include a Blue Marble flag either on the outside of the CM or the skin for the LMM. I assume this is farily easy to do, I remember you having the CSTART logo on some of the Selene renders?
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Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.
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8:58 pm
January 9, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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I know you lengthened the nose at my request so I feel like I'm being demanding by saying anything further about it now, but I think that the current nose is considerably too long. The RCS for Gemini was entirely contained in the nose, including its propellant (this is where I got the idea for that), and the length of their RCS unit was quite small in comparison to ours. They probably used a higher Isp fuel than we will, true, but that spacecraft was also heavier. I think a nose section half as long as the current renders would be a more accurate representation of what we will need. Is this hard to change?
This is an easy change, I'll shorten it in the next concept.
I assume that the tapering of the end of the LMM is motivated by a desire to minimise its mass? Interesting idea, I can't think of any drawbacks to it.
This was essentially the reasoning behind it. Straight beams running from the engine base plate to the bottom of the propelant tanks would have interferred with the lander. Going straight out and then making a 90º turn up would cause unnecessary stress.
Maybe my main concern overall: I'm not sure that the interface between the Mission Extension Module (MEM) and Lunar Mission Module (LMM) is clearly modular enough. Remember that there will be missions flown which are just a CM with a MEM behind it and a small Retro Module (RM – for deorbit burns). This means that the MEM exists as a purely standalone piece of hardware – it's frame should consist of two rings with 4 members joining them. The end of the LMM will have its own frame ring, so at their interface there should be two rings? At first I thought that the fact that the MEM's supply tanks and the LMM's propellant tanks were so tightly nested was a problem for modularity too, but thinking about it, the LMM never has to interface with anything other than the MEM so it's not a problem for the LMM's tanks to protrude a little forward of the front of its frame to accommodate this tight packing. All of this, of course, is how things look from my perspective and how I had interpreted the modularity of our designs, which is not necessarily the way. EDIT: I just noticed you've already mentioned yourself that you haven't properly differentiated the two, sorry for not picking up on this bit originally – too distracted by the pretty pictures!
I wouldn't necessairly call it an oversight on my part so much as it is a simplification for the sake of modeling. After some thinking though, I think that this configuration will still work just fine. The MEM itself is basically composed of the spherical tanks directly under the heat shield along with other components that are not depicted. It is held onto the bottom of the CM by straps (metal, nylon, it doesn't matter). For lunar missions the LMM just fits over the top of the MEM as depicted in these renders.
I'll make new renders of the CM with just the MEM later.
In light of our recent official partnership with One Flag In Space it would be nice to start trying to include a Blue Marble flag either on the outside of the CM or the skin for the LMM. I assume this is farily easy to do, I remember you having the CSTART logo on some of the Selene renders?
In the past I've just used Photoshop to put the logos on the renders. I'm not totally sure if I can do it directly in SketchUP. I'll try to put the logo on my next renders.
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Main Workgroups: Propulsion & Spacecraft Engineering
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9:09 pm
January 9, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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On the topic of the MEM; imagine that the MEM tanks have a support sturcture that is attached to the upper ring (at the bottom of the CM). The upper ring and the MEM tanks (and other MEM equipment) constitutes the MEM. The LMM then attaches to the upper ring with its support legs. I'll have renders in 20 mintues.
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Main Workgroups: Propulsion & Spacecraft Engineering
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9:21 pm
January 9, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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Post edited 3:56 am – January 10, 2010 by Rocket-To-The-Moon
Here is an updated version that shows the MEM and LMM. Thoughts?
Also note the RCS thrusters on the LMM.
Note:
- There is a lot of unused space between the heat shield and the LMM tanks. This space is left empty in the renders for ease of modeling and for clarity. In actuality this space would be occupied with equipment.
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Main Workgroups: Propulsion & Spacecraft Engineering
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10:02 pm
January 9, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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I forgot about shortening the nose, here it is.
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Main Workgroups: Propulsion & Spacecraft Engineering
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10:10 pm
January 9, 2010
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Luke Maurits
| | Adelaide, Australia | |
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This all looks super fantastic. It's a real shame that I don't have more spare time this weekend to comment on this stuff in depth but I have a lot of work I need to get done and I used what solid CSTART time I could spare to kick off the Overview Document (which I'll add these renders to in the near future!). Some extremely quick comments:
- With the Blue Marble flag, what I actually had in mind was it being applied as a texture to the CM or maybe the LMM skin, the way the CSTART name and logo has been in this picture of Selene 1, not just beside the render. I'm not sure if you realised this and the current images are just a temporary fix, but I just wanted to make sure. It's not a huge priority, anyway. Of course, the CSTART logo should feature on the CM as well, not just the Blue Marble.
- I think I like what you've done with the frame of the MEM, making it as small as possible. My only concern is that the Retro Module would ideally need to be attachable either directly to the CM (for orbital flights < 24 hours in duration) or the to the back of the MEM (for orbital flights > 24 hours in duration). I had in mind that the MEM would be cylindrical so that this would work without problem, but if we can think of a way to make this arrangement work with the smaller MEM that would be ideal. I suppose the RM will be fairly small as well, maybe if we made it the size of the smaller circle of your MEM we could attach it either directly behind a MEM or use a reducing adaptor frame like the MEM's to attach it to the CM. Sorry if this is unclear, I can make quick sketches if you need them.
Sorry, that's all I have time for for now, but great work, this is excellent looking stuff.
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Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.
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10:18 pm
January 9, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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With the Blue Marble flag, what I actually had in mind was it being applied as a texture to the CM or maybe the LMM skin, the way the CSTART name and logo has been in this picture of Selene 1, not just beside the render. I'm not sure if you realised this and the current images are just a temporary fix, but I just wanted to make sure. It's not a huge priority, anyway. Of course, the CSTART logo should feature on the CM as well, not just the Blue Marble.
I briefly tried to do this in Photoshop but I wasn't satisfied with the result. I was having a difficult time getting the flag to match the contour of the CM. It looked okay, but a little out of place. I'll see if I can do this in the future.
I think I like what you've done with the frame of the MEM, making it as small as possible. My only concern is that the Retro Module would ideally need to be attachable either directly to the CM (for orbital flights < 24 hours in duration) or the to the back of the MEM (for orbital flights > 24 hours in duration). I had in mind that the MEM would be cylindrical so that this would work without problem, but if we can think of a way to make this arrangement work with the smaller MEM that would be ideal. I suppose the RM will be fairly small as well, maybe if we made it the size of the smaller circle of your MEM we could attach it either directly behind a MEM or use a reducing adaptor frame like the MEM's to attach it to the CM. Sorry if this is unclear, I can make quick sketches if you need them.
Could we have a retro rocket in the tip of the nose for the orbital flights? Burn this rocket to deorbit and then use the RCS to orient it? Just a thought.
I'm off to bed, this has been a productive day.
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Main Workgroups: Propulsion & Spacecraft Engineering
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11:07 pm
January 9, 2010
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Luke Maurits
| | Adelaide, Australia | |
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| posts 1483 | |
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Rocket-To-The-Moon said:
Could we have a retro rocket in the tip of the nose for the orbital flights? Burn this rocket to deorbit and then use the RCS to orient it? Just a thought.
A very intereting idea, I hadn't thought of this.
This would save (very slightly) on RCS propellant since there wouldn't be a need to turn the capsule through 180 degrees before the deorbit burn, since the nose rocket would already be pointed in a retrograde position. We could eject the retro module from the nose after it had fired to give the parachute module room to open. It would also simplify the stacking up of various modules for different missions.
This is definitely worth considering, it may be the best approach overall. I will give it some more thought.
We could probably use more thought on RCS and orbital maneuvering in general. The set of 8 jets (in orthogonal pairs) in the nose, taken from Gemini, allows the rolling of the CM without any translation, but pitch and yaw both involve some simultaneous translation. Is this hugely problematic? It could only be avoided by having RCS thrust at the rear of the module too, to keep the net force on the module zero. A rear-mounted retro module could take care of this as well as deorbit burns, which may be an argument in favour of that approach over a nose retro unit – but it may be that the translation is not a huge problem. It wouldi be if we had to do precision docking with the CM, but none of our plans so far call for that.
For the sake of clarity and making sure we don't overlook anything in our structural planning in this thread, here are all the mission configurations we may want to fly and what may be involved. Assuming "forward" is left to right:
- Suborbital flights: Trivially only one option, CM.
- Brief orbital flights: Two options: rear-retro, RM-CM or nose-retro, CM-RM.
- Lengthy orbital flights: Two options again: RM-MEM-CM or MEM-CM-RM depending on rear or nose retro.
- High apogee orbital flights or circumlunar: PM-MEM-CM, where Propulsion Module PM is our "Orbital bus" idea – no retro required here because PM can do it.
- Lunar flights: LMM-MEM-CM, where LMM, no retro required because LMM can do it.
So, no matter what we do retro-wise:
- The CM needs to be able to have a MEM behind it.
- The CM needs to be able to have a RM either behind it or in the nose.
- The MEM needs to be able to have a PM or LMM behind it.
- The MEM may have to be able to have a RM behind it if we don't go with the nose option.
Sleep well, Rocket, you have definitely earned it!
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Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.
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6:28 am
January 10, 2010
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brmj
| | Rochester, New York, United States | |
| Member | posts 402 | |
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My take on this: I like the way this is heading, if we stick with plan bravo. Here's a few specific things:
- I really like the retro-rocket on the nose idea. We might even be able to get away with using an off the shelf solid rocket engine intended for high powered model rocketry, since we would no longer have such a length constraint.
- We could probably make the entire stack somewhat shorter by designing the lander with a folding seat.
- On the RCS issue: I am confident that this is basically a software issue, and thus manageable, as long as we pick any reasonable design. I may have missed something important, though.
- I think minimizing the differences between the PM an LLM is vital to keeping complexity down. Shouldn't be too difficult.
- Do we have any reasonable estimates on how big of tanks we need for the purpose of these concept renders, or are we still just going off of some guess that got made however long ago? If there aren't good numbers here, I don't think we should be putting too much faith in these renders for the purpose of whether or not it will fit in a given payload fairing.
- I kind of like the way things are going with the commercial booster option. As cool as our own launch vehicle could be, this will simplify things going forward. If it looks like we could save money by building our own, though, I would still be open to it.
I think that's it for now, but I'll add things as I think of them. Good work, people! Sorry I kind of dropped off of the face of the internet for a while.
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Main work groups: Propulsion (booster), Spacecraft Engineering, Computer Systems, Navigation and Guidance (software)
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7:08 am
January 10, 2010
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Luke Maurits
| | Adelaide, Australia | |
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| posts 1483 | |
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If we only have the 8 jets in the nose for RCS, no software will enable us to pitch or yaw without translation. The only way to avoid simultaneous translation during pitch and yaw burns is to maintain zero net force on the CM. This necessarily requires that any thrust up is matched by one down (and vice versa) and any thrust left is matched by one right (and vice versa). The only way to do this while still applying a torque to the CM is to have two sets of jets.
With the tank sizes, this is something I really want to settle too. We have mass figures for the propellants, turning these into volumes requires knowing the density of the propellants, which varies with pressure. I don't know what a sensible pressure for storing the propellants at is and that's what we really need to know to settle the issue.
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Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.
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7:47 am
January 10, 2010
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brmj
| | Rochester, New York, United States | |
| Member | posts 402 | |
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Luke Maurits said:
If we only have the 8 jets in the nose for RCS, no software will enable us to pitch or yaw without translation. The only way to avoid simultaneous translation during pitch and yaw burns is to maintain zero net force on the CM. This necessarily requires that any thrust up is matched by one down (and vice versa) and any thrust left is matched by one right (and vice versa). The only way to do this while still applying a torque to the CM is to have two sets of jets.
This is what I get for staying up all night hacking, then trying to contribute productively. I stand corrected. Sorry for my moment of stupidity.
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Main work groups: Propulsion (booster), Spacecraft Engineering, Computer Systems, Navigation and Guidance (software)
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