Mars Orbiter Carrier

[rogers_buck]

The purpose of this thread is to describe a potential architecture for orbital Mars probes that would have distinct advantages of cost, time, and mission adaptability.<br /><br />The heart of the system is a large orbiter placed in a polar science orbit. The orbiter would provide high bandwidth communications, power, attitude, and stability systems and would include several docking bays for instrumentation. The orbiter would likely be launched on a heavy booster and use aerobraking to achieve the desired orbit. This part of the system will be referred to as the carrier.<br /><br />The seconad part of the system are instruments that are launched on smaller boosters with adequate systems to support cruise, aerobraking, and autonomous rendevuez and docking with the carrier. These modules will be referred to as insturment modules.<br /><br />A third part of the system are consumable supply mdules that provide the same cruise, aerobraking and autonomous docking capabilities as the instrument modules, but will be used as resupply tankers for consumables. These modules will be referred to as supply modules.<br /><br />These three components, carrier, instrument modules, and supply modules, constitute the basic components of the system. It is possible that it may be desireable to also modularize communications and attitude control components if the economics and logistics make sense.<br /><br />In the basic scenario, the carrier is launched and placed in the desired martian orbit. Subsequent to achieving orbit, an initial constellation of instrument modules are launched after the carrier is checked out and declared operational. The instrument modules arrive at mars locale and aerobrake. The autonomous docking systems then deliver the instrument module to the designated docking port on the carrier. Once docked, the instrument connects to the systems of the carrier through a standard bus and ground controllers check-out and certify the instrument for scientific use.<br /><br />

 

[rogers_buck]

My assumption is that the requirements for these systems would be far less rigorous for a dormant insturment cruise stage than as for operation on orbit. If that isn't the case, then I'm surprised and the economics fall through the cracks.<br />

 

[rocketman5000]

Wouldn't this system either require hideous amounts of instrument propellants or a very sensitive launch window to match the orbits upon arrival at Mars??

 

[rogers_buck]

The thought is that the instrument module would be far less massive than, say Mars Observer. So each dip in the martian atmosphere would slow it faster than Mars Observer was slowed. It might even emply a balute. <br /><br />Circularizing the orbit after that to meet up with the carrier is a good question. More energy would be required for the instrument+cruise stage than would be required if the instrument were part of the carrier because the carrier would have the economy of a shared engine.<br /><br />I don't know how big a factor that would be off-hand. I guess it depends on the ratio o the mass of the flight hardware (motor, guidance, etc.) to the propellant.<br /><br />BUT, that simple economy only applies to the initial constellation of instruments. If you have two or three generations then the economics of the carrier certainly prevail.<br />

 

[SpaceKiwi]

Interesting.<br /><br />Do you want to flesh out the architecture on this a little. I assume you are thinking along the lines of an ISS Node- type module for the Carrier? That would assume six attach points, less two for solar arrays (unless you are using nuke prop on this?).<br /><br />Can the instrument packages "piggy-back" out from the initial four attached to the Carrier? I guess this depends on how many packages you want to deploy, but I would suggest the more the more cost-effective the overall project would be. You would obviously need electrical and data pass-throughs from the main bus if you are going to use such a piggy-back method.<br /><br />Aerobraking and the ability to rendevous. Is this a viable option? I am unfamiliar with the accuracy of aerobraking as it might pertain to bringing two or more objects together in space. Getting a satellite into a circularized orbit within a nautical mile or so is one thing. Bringing a second object in to dock with that, where you are talking about precision in terms of centimetres, is quite another. You would want to keep prop on the instrument packages to an absolute minimum.<br /><br />The modular nature of the idea does present good advantages in the areas you describe, and particularly with allowing international co-operation to a standardised schematic and the incremental financing aspects. However, I do wonder if the total cost might not be much more significant than starting with a "super-sat" platform to begin with ... the whole Freedom vs ISS argument I guess. <div class="Discussion_UserSignature"> <p><em><font size="2" color="#ff0000">Who is this superhero?  Henry, the mild-mannered janitor ... could be!</font></em></p><p><em><font size="2">-------------------------------------------------------------------------------------------</font></em></p><p><font size="5">Bring Back The Black!</font></p> </div>

 

[rogers_buck]

responding to both of you...<br /><br />As an engineer, I tend not to try to engineer these things because it is not my field. The devil lies in the details and there is always plenty of good filters once the engineering cycle begins. However, I think airing a basic concept here and giving it enough imagineering to identify flaws or merits is a good practice. I consider this to be the engineering equivalent of the "upper" or "lower" limit in science.<br /><br />Those who have posted in this thread have quickly identified the key questions as to the economics of this proposed architecture. Unfortunately, I cannot address these key factors beyond the level of speculation. I can apply Moores law to the guidance and detectors, but I cannot speak to the performance of rocketeering and aerobraking to a circular orbit. <br /><br />One thing that does occur, is that if the economies of the shared cruise stage are greater than that of a plurality of smaller cruise stages, such an approach is not precluded in this architecture. What I mean by that is that a cruise carrier of an entire constelation of new instruments could be launched on a large booster with a robust cruise and rendevuez stage. The entire cadrey of instruments would be changed out with one such follow-on mission. In that case, the question of economics becomes whether is is cheaper to provide the systems that allow module swapping vs. replacement of the entire vehicle on orbit?<br /><br />There are probably multiple answers to that question that all depend on the complexity, capability, and longevity of the carrier. If the carrier is nuke, in addition to the economics their is the risk mitigation of not launching multiple nukes (percieved or otherwise). Given that the systems of automation are all adherents of Moores law, and the rest of the vehicle is an economic monolith, I think the answer is invariably that is cheaper to reuse the systems on orbit at the expense of added automation.<br /><br />I would like

 

[rocketman5000]

Maritan rendezvous would require a large amount of automation. However it might be possible to use orbiters currently at the planet as location beacons. <br /><br />Since I am not the strongest on orbital mechanics I wonder if someone could confirm this idea: if the instrument could maneuver into the correct orbital plane as your Carrier module if it dipped really deep into the atmosphere and used aerodynamic surfaces while aerobrakeing to track sideways in its orbit? Might be only able to move a couple of miles sideways, but this movement would essentially be free. <br /><br />Finally if you attached some sort of coil and capacitor to the instrument package you might be able to eject the spent instrument cruise stage into a retrograde orbit and circulize the orbit of the instrument. All the this I suggested however are highly speculative. To my knowledge never tried in orbit.

 

[rogers_buck]

Its a question of specific impulse. If you need to change the orbit by 10s or hundreds of meters per second, then kicking awasy the cruise stage to produce the needed delta-v would likely be fatal. However, if you need to make a fine adjustment then you probably are already where you need to be.<br /><br />There are a few technologies I think would be interesting. One is micro-explosives arrays. These could be used for final approach adjustments and would be less complex than combustion/expansion systems.<br /><br />I like your idea of "flying" aerodynamically in the martian atmosphere. The cruise stage would need to be computationally extremely potent to analyze and navigate in realtime, no help possible from the ground. I like this because it is trading fuel mass for computational complexity which has well demonstrated economics. Knowing where it is at would be of vital importance for such a manuever just as being able to measure the ambient conditions. Perhaps the siting of a martian on-demand GPS analog would be a requirement.<br /><br /><br /><br />

 

[j05h]

Wouldn't it be easier to deal with this by designing a modular system that is integrated on the ground? ESA's Venus Express is like this, a basic bus (it's the backup Mars Express hardware) that they attached new instruments to. SpaceDev's NEAP was going to be like this, too. A generalized deep space bus that could be customized based on needs. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[scottb50]

If our only effort is to send a continuing stream of sensors to Mars then your proposal makes sense. I think we have sent enough probes to be confident in sending a manned mission, which, I thought, was the reason for the past, current and near future probes.<br /><br />We've put men on the moon but now we seem to have to recreate the entire process. Orbital sensors, landers and then finally, in another 13 years a manned mission. <br /><br />I find it sad that an Astronaut who walked on the moon won't be around to provide commentary for the first return, they'll all be dead by then. <div class="Discussion_UserSignature"> </div>

 

[rogers_buck]

Sure. Modular design can/has lowered the cost of space probes and earth communications sats. It is fair to consider such economies when pondering this proposed architecture.<br /><br />Let's say that a probe+launcher cost of $250M is achievable for a fully integrated probe with a constellation of instruments designed for a specific line of enquiry. The probe has an estimated life of 10 years and there is a hard cost associated with operating the probe every year. As a valuable asset the probe will be kept active after the science value of its instruments have been superceeded by new lines of enquiry, subsequent arrivals of new probes, and new technology. The husbandry of each probe is cradle to grave and has a budget of $x million/year on average.<br /><br />With the carrier concept, the initial cost of the probe would be higher but its productive lifetime could be more than doubled. By productive, I mean premium science lifetime. Instead of having to launch and manage $250M follow-on missions there would be a stream of new instruments autonomously arriving to keep the carrier at the cutting edge. The superior facilities of the carrier (power, communications) would compress the timeline for data collection allowing the probe to service a broader range of science channels simultaneously. No lost productivity waiting for download scheduling,etc.. These are all soft costs but they translate to real dollars. Of course, the data relay concept that NASA has planned also has this advantage and the economics of a big communication pioe provides the justification.<br /><br />Also in the soft cost column is the integration and staging of building a mars probe. In the carrier architecture the instrument modules are standard and produced to specifications with simulators and testware available to each instrument developer. This soft cost is actually a benifit of the modular concept as you describe as well, but the advantages of the carrier concept is that only one instru

 

[rogers_buck]

Flags and footprints are fun, but as we saw with Apollo they have little long-term value. Before we send humans we need to know where all the resources are that can support long-term stays and even colinization possible. Remote sensing and robotic missions will be necessary to make intelligent planning of manned missions a success. The astronauts are great men, but in the end they were payload to the dreams and aspirations of many humans with a common dream. In the course of human history 50 or 100 years has been short term with respect to settling far more hospitable environments. We must be patient. The incredible cost to send men must be worthwhile or it will not be sustainable.<br /><br />

 

[j05h]

<i>> So would a $1B carrier with maybe 20 $50M instrument module launches be better economics than 5 $250M missions over a span of 20 years once all of the hard and soft costs are factored in? Probably, especially if a good number of the instrument modules are funded by foreign or commercial interests. </i><br /><br />I am discussing a commercial concept, extended from the Mars/Venus Express and Iridium system. The basic Iridium sats only cost around $10m each in bulk. SpaceDev's NEAP platform has canisters of some size for other's payloads, if they fly it. There is no need for a Billion Dollar Carrier - you want a fairly simple platform that does comm, maneuvering and power. You want it capable, but you want to build a lot of them. Through the series, the vehicles are designed to play nice with each other - each should function as a "file sharing" node to handle data and commands. It should neatly double as a GPS system via triangulation in software. Something like this can be the baseline on which another organization provides specific instruments. It's a lot of cash, but the basic platform should be more like Iridium costs than MRO costs especially if offered commercially. How much would a 10kg spectrometer cost onboard? How much does bandwidth cost over the years? <br /><br />For NASA exploration, I'd definitely take the 5 missions over 20 years (current strategy, roughly) over the Billion Dollar Mega Mission (Vikings). Instruments improve.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>