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6:42 pm
November 28, 2009
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brmj
| | Rochester, New York, United States | |
| Member | posts 402 | |
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Post edited 1:00 am – November 29, 2009 by brmj
This is based in part on a combination of Rocket-To-The-Moon's recent design, Luke's recent post in this subforum and the results of the real time wave that occurred a little over a week ago, along with some original thought. This design was thought up with future usefulness in mind, as well. Here it goes.
My proposal is to develop a system of RCS, navigation and guidance sensors and computers, communications gear and a power supply that can use very, very similar hardware and underlying software. One such system would be integrated into the command module, while another would be integrated into the lander. These systems would know how to control a standardized "Orbital Bus", which would contain engines, fuel and very little else, except possibly a power system. The orbital bus would have enough fuel for a one way trip to the moon with the CM, plus a low energy transfer with the lander. The lander's engine and fuel tanks would be derived from the orbital bus as well, and would have the same software-level interface. Our CM would be largely self-contained, and would be suitable for orbital, sub-orbital and lunar missions.
EDIT: I am thinking that liquid hydrogen and oxygen might be worth considering as the fuel for the orbital bus and lander. This is because it is lighter weight than hypergolic fuels, and it could more easily be refueled with materials producible on the moon. The second consideration is irrelevant for our mission, but it could be advantageous for future missions. Bill Stone is apparently trying to create a commercial fuel-production base on the moon as described in the second half of this TED talk, and if our craft could use the fuel they produce, it would put us in a really, really good position for the future.
Our mission would go as follows: our lander would launch with an orbital bus and would use it and its RCS system to travel to the moon along a low energy transfer orbit. After establishing lunar orbit, our CM would launch with an orbital bus and use its orbital bus and built in RCS system to rendezvous with the lander. Our astronaut would then EVA, detach the lander and CM from their respective orbital buses, attach the lander's bus to the CM, ensure it is working correctly, then land on the moon, do awesome sciencey stuff and come back. After that, the CM would use its new orbital bus to return to earth and de-orbit itself, separate from the bus by way of explosive bolts and cartridge-actuated cable cutters and land safely.
Advantages of this plan that I have thought of would be lower launch weight, fewer things to design, simpler software, and the potential to use the orbital bus, fitted with the same standardized package that goes on the lander and CM, as the central component of any number of unmanned missions latter on. Disadvantages would be a slightly heavier lander and more complex EVA requirements.
Thoughts?
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Main work groups: Propulsion (booster), Spacecraft Engineering, Computer Systems, Navigation and Guidance (software)
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7:22 pm
November 28, 2009
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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Just to clarify for those not involved in the original wave.
- Since the lander is using a low energy transfer orbit the rocket can lift a heavier load to orbit.
- The lander's "orbital bus" would reach lunar orbit with a large percentage of its fuel remaining
- The CM is launched directly to the moon. Its orbital bus consumes most of its fuel.
- Upon completing lunar orbit rendezvous between the CM and Lander the astronaut physically transfers the Lander's bus to the CM since it still has fuel (for the return trip).
My main concern is that this could prove to be an extremely difficult EVA. Is there a huge disadvantage to simply transferring fuel instead of a physical swap?
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Main Workgroups: Propulsion & Spacecraft Engineering
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7:48 pm
November 28, 2009
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brmj
| | Rochester, New York, United States | |
| Member | posts 402 | |
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You know, transfering fuel might be the better way after all, particularly, if we have a second set of removable fuel tanks on the lander such that it has lower landing mass. My concern was that transfering fuel might be technically challenging with a light weight system, and could be exceptionally dangerous if we used hypergolic propelents.
Either way, I think that the basic ideas I expressed about how to seperate out functions is sound.
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Main work groups: Propulsion (booster), Spacecraft Engineering, Computer Systems, Navigation and Guidance (software)
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9:08 pm
November 28, 2009
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perpindicular
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i like this orbital bus idea a lot but i have a couple of suggestions for themission plan in whole
i personally believe we should use a commercial launch vehicle, if possible the shuttle or a soyuz or delta iv. I'm not sure what the load capabilities are of the soyuz but hopefully it should work. what i think would be a great plan would be to have the vehicle shipped to ISS and use one of ISS"s docking ports to hold it there. Subsequently, one of our astronauts would ride a soyuz or the shuttle (All the shuttle missions may already be planned so we may have to go with soyuz if we use this plan) to ISS. From ISS, we would coordinate with ground crew and supply the ship (food, EVA packs, etc). If we get this going, NASA would most likely work with us on the mission communications and consulting. it should be then possible to launch from ISS to the moon at the appropriate time. On the return back, instead of worrying about atmosphere re-entry, we would re-connect with ISS, do mission analysis, maybe some publicity stuff, and our astronaut would head home aboard the next flight.
we would save on fuel and some other things, but we would be putting that money up on paying for shipping the vehicle to ISS as well as our astronaut .
Just a thought i had the other day.
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7:51 am
November 29, 2009
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Luke Maurits
| | Adelaide, Australia | |
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Post edited 2:24 am – November 30, 2009 by Luke Maurits
I have to be honest, my first reaction to this proposal (EDIT FOR CLARITY: The NASA/ISS proposal, not the orbital bus proposal) was very negative. But then I collected myself and decided that it was important not to dismiss so much cooperation with NASA out of hand due to "Not Going to be Invented Here" syndrome. Just because it is way more fun and cool to do everything ourselves doesn't mean we should jump away from what might be hugely simpler or cheaper approaches.
However, even after some reconsideration, I'm still not a huge fan. My biggest concerns would be:
- While I'm sure NASA would be open to the idea of cooperation with us (and I'm not inherrently opposed to it), NASA are actually hoping to return to the moon in the near future themselves. I don't know how keen they would be to help us steal their thunder.
- The Common Berthing System (or whatever it is called) for docking with the ISS is a pretty complicated system, way more complicated and presumably expensive than anything we would ever be inclined to build otherwise (simplicity is our motto!).
- I am pretty sure NASA wouldn't let us anywhere near the ISS unless we passed a pretty serious inspection and testing of our docking hardware, RCS, etc. A botched amateur docking attempt could do a lot of expensive damage to what is probably one of their most valuable assets right now. In the time it would take to jump through all their bureaucratic hoops, we could probably develop a lot of technology and raise a lot of money ourselves.
- Finally, I feel like a large part of the spirit of CSTART, in addition to the whole open source, open data model, is to demonstrate to the world that manned space travel and scientific research in space is something that can now be done by non-government agencies, or at least that it is close to being that and that we can help it become that. Admittedly this is not in writing anywhere (yet), but I think a lot of people would agree that we are trying to follow in the footsteps of people like the Civilian Space eXploration Team, Scaled Composites, Armadillo Aerospace, etc. By effectively paying NASA to take care of the hardest parts of our mission we would actually be sending the opposite message – that private space enterprises are still dependent on huge government agencies.
I don't mean to be too negative or offensive with this post. It's important that we consider and discuss all our options, and bringing up the prospect of collaboration with existing space agencies is a good measure toward that. If anybody wants to shoot holes in my arguments above or just doesn't agree with me with the stuff about the "spirit" of CSTART, go for your lives.
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Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.
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8:53 pm
November 29, 2009
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Luke Maurits
| | Adelaide, Australia | |
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brmj said:
EDIT: I am thinking that liquid hydrogen and oxygen might be worth considering as the fuel for the orbital bus and lander. This is because it is lighter weight than hypergolic fuels, and it could more easily be refueled with materials producible on the moon. The second consideration is irrelevant for our mission, but it could be advantageous for future missions. Bill Stone is apparently trying to create a commercial fuel-production base on the moon as described in the second half of this TED talk, and if our craft could use the fuel they produce, it would put us in a really, really good position for the future.
This might even be necessary just to keep things feasible. Total mass of (cryogenic) propellants for the Apollo SM engine was a whopping 18,413 kg. Using an even heavier hypergolic fuel system would make the mass of an orbital bus really high. Granted, the Apollo CM was 5,809 kg and the SM had 1,200 kg of electrical stuff in it, which is a lot more than we can expect, but I still think our fuel mass will be high.
Hmm. Back-of-envelope time:
Mercury was a one-man capsule like our "CM" will be (does it make sense to keep calling it a CM if there is no SM?) and weighed 1,935 kg, but it was too small and simple for a lunar trip – this should be an underestimate of our CM mass using 50 year old technology. Gemini was capable of a lunar trip like we want and weighed 3,851 kg, but it had a crew of two whereas we only want one – this should be an overestimate of our CM mass using 50 year old tech. Averaging the two vehicle masses gives us 2,893 kg, using old tech. Assuming we can achieve 75% of that by modernising, we have 2,170 kg. This is about 30% of Apollo CM + electrical equipment in SM.
So, assuming we can build an engine as efficient as the Apollo SM's, we'd need about 0.3*18,413 = 5,524 kg of propellant going the cryogenic route. That's better than I expected. Still, I wouldn't like to go higher than that by using hypergolic fuels.
Of course, accounting for the mass of the engine itself and whatever else the bus needs (a power solution, some electronics, micrometeoroid shielding) we are probably looking at closer to 10,000 kg for a bus. This means our CM+bus launch will have a total payload of about 12,000 kg, the lander+bus launch less, probably under 11,000 kg.
Those are fairly scary amounts, but of course our earliest launches will be a CM only (suborbital) and then a CM + "mini bus" (orbital). We will have time to work up to the 12,000 kg launch, tech-wise and money-wise.
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Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.
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9:52 pm
November 29, 2009
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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It is good to see some rough mass estimates. I have a feeling that we will be able to beat your estimates assuming that we keep to our "simple" design philosophy. The entirety of the electronics (sensors, wires, computer) could probably be under 15kg for the CM. Adding communication gear will add some to that total but I still think that we will be leaps and bounds above anything from the Mercury/Gemini programs.
If we make the capsule out of some modern lightweight material like carbon fiber that will serve to reduce the mass even more. By "Doing the simplest thing that could possibly work" I believe that we will put ourselves in a real good position.
Every kg less that the CM weighs is that much less propellant that is needed (both the "bus" and the booster). Pretty much everything is lighter and stronger now than it was in the past. We can use LED lighting which reduces mass directly, but it also requires smaller batteries (which themselves are lighter).
Ultimately mass is everything. Too much and we are dead.
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Main Workgroups: Propulsion & Spacecraft Engineering
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10:22 pm
November 29, 2009
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Luke Maurits
| | Adelaide, Australia | |
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We may very well be able to beat those estimates. If nothing else, they should provide realistic upper bounds – we should be able to avoid exceeding those estimates if we don't do anything stupid.
I don't know much about structural engineering, is carbon fiber really the kind of thing you can make a command module out of? Isn't it prone to shatter under high stress?
I have a friend who is a structural engineer who is interested in this project. He has just come back from an interstate trip which prevented him from looking at it too much until now, but I advised him to look around the Wiki and he may turn up in the forums soon. Hopefully he can advise on a material that is lightweight but appropriate, and also point us in the direction of the kinds of considerations we need to make to ensure the module can withstand all the appropriate trials we will subject it to.
My gut feeling is that while we will certainly be able to beat the crap out of Mercury / Gemini when it comes to the mass of electronics etc., we may not be able to do that much better when it comes to structural mass. Gemini already made extensive use of titanium and aluminium, which have pretty good strength to weight ratios.
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Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.
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3:41 am
November 30, 2009
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Luke Maurits
| | Adelaide, Australia | |
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| posts 1483 | |
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I've just realised I goofed up and the Apollo SM didn't use cryogenic propellants at all. The engine (the AJ-10, which apparently NASA want to use again for their new moon project!) was, in fact, hypergolic. This means if we did go the cryogenic route, we'd need less than my earlier estimate of 5,524 kg of fuel. How much less, I don't know.
Of course, between hypergolic and cryogenic, hypergolic is definitely the simpler thing to do. Simplicity is supposed to be our guiding principle, but I think in cases where a more complex option can save us thousands of kilograms of payload, complexity could be worth the price.
I'm a bit stunned by NASA reusing the AJ-10 for Constellation. I mean, sure, "if it ain't broke, don't fix it" is a fine rule of thumb, but surely there have been significant increases in engine efficiency since Apollo? Are they just trying to save on R&D and testing of a new engine?
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Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.
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4:53 am
November 30, 2009
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Luke Maurits
| | Adelaide, Australia | |
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| posts 1483 | |
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This is a pretty crazy idea, but I'll throw it out there.
Instead of various complicated EVA plans which involve physically moving fuel tanks or orbital buses, etc., would it be feasible to have the CM be "towed" by orbital buses? I am imagining a fairly sturdy cable linkng the two, with the bus in front, pulling the CM along. Switching from the bus the CM was launched with to the lander's bus would be a case of severing the first cable, getting the CM behind the lander's bus and firing some sort of magnetic harpoon at it. It may be hard to do that accurately, but we could probably take multiple shots at it, and it feels like it would be easier than docking with buses or manuall moving things during EVA.
Like I said, it's a little nuts and there would be issues to solve (the cable would need to attach near the centre of mass of the bus to keep things in line, but that means either the cable gets very near the engine and hence hot exhaust, or we have multiple smaller engines which are off-centre but placed symmetrically), but at least all the bus exchange stuff could happen with the astronaut safely inside the CM.
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Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.
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