CLCACS "klickacs"

[GIThruster]

Cis-Lunar Collision Avoidance and Communications System: CLCACS "klickacs"


If anyone here is interested, I'm curious to see the numbers of what it would take to install a single facility at Lunar L1, that can provide interesting levels of surveillance, tracking and communications throughout cislunar space.

In order to launch a radar and communications array that can promote future space development and watch for Near Earth Objects, one needs a dielectric that can shrink the size and mass of a metallic antenna array hugely, and even that of a normal dielectric array by a serious factor. We're talking about the kind of array that one could compare to the ALTAIR array on Kwajalein--something on the order of a 10 MW installation. Even using a dielectric with astonishing qualities, we're talking about a BIG array. So here's what I'm wondering.

One wants to look at the mass a Falcon 9, a Falcon Heavy and SLS can loft to Lunar L1 and see if it is feasible to put several tons up with a single launch, then use several launches. If for example, one of these launch vehicles can lift 5T to LL1, then one could conceivably build a very large array with 6 launches.

In such an array, you might for example stipulate a hexagon assembly. each of the six trusses of that assembly could be launched as a single, light weight carbon fiber, hexagonal cross section craft of about 70 meters long and 5 meters diameter and storing PV panels and power equipment inside for launch; that when unfolded at LL1, would provide ~20? X 70 ~=1,400 square meters surface area facing one direction. Six such trusses could then be connected in a hexagon that lies radially on the plane of the Earth's orbit around the sun, at LL1. If one placed a light-weight ceramic dielectric antenna every 10cm on such a surface, they'd have an array of about 140,000 elements per truss. Such an array would be able to scan in all the important directions at once, send and receive both radar and VHF/UHF communications (300 Mhz) and could be capable of some astonishing feats.

For example, it appears to me possible such an array could track objects across all cislunar space down to a reasonable limit defined by their distance, but perhaps on the order of a golfball at greatest range. It is possible, such an array could repeat UHF communications from a lunar astronaut's suit, back to any lunar surface vehicle, any vehicle in cislunar space and even direct back to Earth. It's possible such an array could even track a Chinese lunar rover on the surface of the Moon--something DoD would take an interest in.

The point, is to consider what is in the realm of the possible and what is not. If we stipulate we have a next generation ceramic with a dielectric constant of 40,000 at 300 Mhz, this can be used to shrink a full wave antenna from 1 meter, to 0.5cm. A 1cm diameter antenna of this sort could send and receive with astonishing power. Put 840,000 of them into a single installation at the right point, and even one in the top of an astronaut's helmet, and there's no telling what is possible, at least without some calculation.

Certainly, such an array truss as proposed would weigh on the order of several tons. So first things first. Can Falcon 9, Falcon Heavy, or SLS loft several tons to LL1?

Secondly, given the distance between Earth and Luna, ~406,000 km; and the Lagrangian point between them as defined here in the first equation under "Mathematical details":

http://en.wikipedia.org/wiki/Lagrangian_point

how far would a transmitter on the Moon need to send to such an installation? How far would the installation need to be able to sense objects in space of sufficient size to be considered great threats to future spacecraft? 300,000 km? Is is reasonable to presume an array on the order of 50 MW transmitter power could cover all cislunar space in useful fashion? (Remember, radar transmitters only transmit periodically, so there is no trouble with collecting power at far less rate than using it to transmit. 1 MW installed PV power is likely more than necessary for a 50 MW array, and if each installation truss holds 2, 5mX65m PV panels, that is a lot of installed power. Just guessing but probably more than ISS by a factor or more.)

These are the kinds of questions I'm asking myself since this is the kind of project one could sell both NASA and DoD on, and that would eventually make it possible to build the spaceships. So it's a serious consideration. Anyone who wants to play with the numbers, please do share. I can't afford an engineer for this right now, and it would be great if there were enough answers to at least spark the interest of a radar and communications antenna miniaturization specialist I have in mind.

Falcon 9 launched the Deep Space Climate Observatory to Solar L1 and it weighs 570 kg. Is the energy requirement to Solar L1 smaller, larger or the same as to Lunar L1?

Note NASA's interest here:

http://www.nasa.gov/pdf/604657main_4-%2 ... bskill.pdf

[GIThruster]

I'm not sure this is useful: http://ntrs.nasa.gov/archive/nasa/casi. ... 001435.pdf

On page 2, you'll find that the dV for LEO in 2 days is 10km/s and from LEO to LL1, 4km/s. Does this give a mission profile for max mass to LL1?

I was under the impression one can't use delta V calculations without constraining oneself to the mission trajectory it's used for, and that dV is therefore not a useful tool for much past mission planning. For a slower trip you don't need as much dV. But if this gives a 2-3 week max dV for Earth to LL1 of 14km/s, this would seem useful.

Page 5 they say SSL can send 10T to LL1.

[krenshala]

I'm not sure this is useful: http://ntrs.nasa.gov/archive/nasa/casi. ... 001435.pdf

On page 2, you'll find that the dV for LEO in 2 days is 10km/s and from LEO to LL1, 4km/s. Does this give a mission profile for max mass to LL1?

I was under the impression one can't use delta V calculations without constraining oneself to the mission trajectory it's used for, and that dV is therefore not a useful tool for much past mission planning. For a slower trip you don't need as much dV. But if this gives a 2-3 week max dV for Earth to LL1 of 14km/s, this would seem useful.

Delta-V doesn't care about what engine you have, the thrust-to-weight ratio of the engines, nor what the mass of the vessel/object is. It only cares about how much your velocity much change to get from point A to point B. If you have a bigger ship you need either bigger or more efficient engines, or just more fuel, to achieve the same dV. So, when planning a trip, you calculate the needed dV, and then from that what fuel/engines you would need for your planned payload mass and adjust accordingly.

It takes a dV of ~9.5km/s to launch to LEO (and the same amount to deorbit, though atmospheric drag/aerobraking provides most of that). It takes an additional ~4km/s to go from LEO to GEO (geostationary). The delta-V map I used to get these numbers doesn't list the Lagrange points, unfortunately, so I'm not sure what it needs to go from a LEO parking orbit to L1.

(Heh, all my mission planning in Kerbal Space Program is paying off in this topic! )

[93143]

10 km/s is a rough estimate of typical launch delta-V; the two days is probably for rendezvous and propellant transfer operations. Delta-V from LEO to EML1 is broadly similar to trans-Mars injection, a little shy of 4 km/s.

That paper is not discussing SLS (assuming that's what you meant by SSL); they're talking about using smaller rockets like the Delta IV Heavy (9-10 tonnes max). Falcon Heavy has a kerosene upper stage and thus wouldn't be much of an improvement, if any, over DIVH (a few tonnes more if crossfeed is used, which it won't be unless someone pays SpaceX to develop it). SLS should be able to put at least 30 tonnes at L1 without advanced boosters.

If you don't mind taking a few months to converge on your destination, you could get to L1 with delta-V comparable to trans-lunar injection using a weak stability boundary trajectory, saving several hundred m/s. This would add a few tonnes to the Delta and Falcon numbers, and SLS would be getting close to 40. I don't think there's a way to do this without spending a lot of time in the Van Allen belts, though (don't quote me on this)...

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I'm not convinced MMOD hazards to spacecraft are anywhere near important enough outside LEO to be used as justification for a project of this magnitude, certainly not in the scenario where we're still using rockets to access space. Planetary defense may be another story, but I don't have the necessary expertise to say.

[GIThruster]

I'm not convinced MMOD hazards to spacecraft are anywhere near important enough outside LEO to be used as justification for a project of this magnitude, certainly not in the scenario where we're still using rockets to access space. Planetary defense may be another story, but I don't have the necessary expertise to say.

Not sure what "MMOD hazards" are but I think we agree. Though I'd love to see this in order to move all collision avoidance expense off future cislunar spacecraft (and thereby reduce their expense and enhance their performance), the main issue here is that both DoD and NASA have Congressional mandates to provide tracking of Near Earth Objects (NEO's). There'a already money for this and given the ceramic I'm looking for funding to develop, we're looking at a solution to a problem Congress already wants to fund. Likewise that DoD would love to provide surveillance and tracking of all man-made objects in Cislunar space, track all lunar movements and have en ear on all the telecommunications in that space. Also note NASA has this fuel depot concept they want to use LL1 (or ELL1 if you like) for, and a single larger installation that serves several purposes is much easier to defend than single solution projects. And there's the ability to monitor all missile launches on half the globe at once--something DoD would love.

Without crunching the numbers much more carefully there's no way to tell whether a single Falcon 9 launch could serve. If the project can be cut down to $100M for each of 6 trusses and $60M for each truss launch, it's vastly easier to get the funding from DoD, NASA or both. Some of this you just can't guess at. Best is develop the metrics in order to make better guesses as you go along. If we can expect a Falcon 9 to lift a 5T package to LL1, then we know what we need to to look at the capabilities of a 5T package.

Lets say you filament wind a 5M diagonal hexagon on a McClean Anderson Raptor, then cut and hinge all the vertices save one which has a clasp. So you have this almost cylinder which opened is 15M X 70M = 1050 square meters. If you can keep this mass down to say, 4 tons, you can add klystrons or traveling wave tubes, the connecting shrouds and not much else, and still be able to launch this to LL1. 6 such launches is ~$360M. If you could bring this project in under $600M, you could sell it for $1B to DoD alone. And you have funding for growing large quantities of dielectric, and wrapping large quantities of ultra-high strength carbon fiber vessel sections.

This is in the price range of the SBX system, which cost roughly $900M and is not space based. A space based system of similar capability, would be able to track missiles rising from any point on half the globe at once, so it's easy to see how USG might fund this sort of project. They might well pay for a second, smaller but similar array just to cover the whole globe.

"The US Missile Defense Agency's Sea-Based X-Band Radar (SBX) is the largest phased array X-band radar in the world - in other words, each of the radar's antennae are individually controlled by its own computer and operates within the X-ray band of the electromagnetic spectrum. Being designed to move around the Pacific Ocean, the actual radar is carried by a mobile, ocean-going semi-submersible oil platform, the entirety of which measures 73 m (240 ft) wide, 118 m (390 ft) long, 85 m(280 ft or 26 storeys) tall and displaces 45,360 tonnes (50,000 tons) of water. Built by Boeing (USA), the SBX cost US$900 million (£504 million) to develop and is powerful enough to distinguish between incoming and decoy missiles. It will be used with other radar installations as part of the American Missile Defense Agency's ground-based midcourse defense program (GMD). The SBX was due to arrive at its home port in Adak, Alaska, USA in late 2006. The protective 'radome' alone measures 31 m (103 ft) high, 36.5 m (120 ft) in diameter and weighs 8,100 kg (18,000 lb). It is supported only by air pressure and can withstand winds speeds of over 209 km/h (130 mph).

According to the US Missile Defense Agency: "The radar is so powerful that if it were off the east coast of the United States near Washington, D.C., it would be capable of detecting the motion and rotation of a baseball launched into outer space from the San Francisco area". http://www.blackanthem.com/scitech/mili ... 11207.html "

http://www.guinnessworldrecords.com/wor ... ay-x-band/

Note too, that launched in this closed configuration, with all the sensing elements facing inward and surrounding the PV arrays, this can loiter in VAB and no delicate components would be vulnerable to damage. The casing which is the array structure, should be quite capable of taking the abuse of the VAB until the truss is out of harm's way. And if not, then there is DST's weather hardening tech to consider. . .

at 1,050 square meters and a 1 cm dia., 0.5 cm long ceramic element every 10 cm, and smallish bits set apart for hinges and gear, we're taking about a 100,000 element array for each truss. If you can grow 20 elements/year/reactor tank, you need about 10,000 tanks in a crystal growth farm, in order to be able to produce enough crystal to build this within 3 years, which is the longest one should consider for a project like this. And that's the need since if this works, there are all the other Lagrange points to consider, and eventually stations on the Moon itself (which are harder since you have to land them.)

A 10,000 tank farm is therefore in the range of a necessary requirement (until better number crunching) and one should expect this alone to cost on the order of $50M. It could easily be $250M, but at least if that happens, this sort of project can find funding. DoD paid Boeing $900M for a ship that can only provide the smallest portion of what CLCACS could.

[93143]

MMOD = micrometeoroids and orbital debris. Perhaps not the best choice of terminology, since you're probably talking about bigger stuff, but bigger stuff is even rarer. Unless spacecraft traffic increases substantially for some unforeseen reason...

I don't know about the idea of having a combination fuel depot/radar array. A cryo depot needs to avoid even small amounts of excess heating, and if it's a powerful enough array it could even be dangerous to humans. That's not even considering electronics and communications. It might work if it were on the opposite side of a halo orbit... I am not an RF/electronics expert, so I can't guarantee that these concerns are well founded, but I also don't see any significant advantage in combining the two stations.

Falcon 9 is probably not capable of 5 tonnes to EML1 even using a WSB trajectory, but if there really is a 30% reusability margin on their GTO number it might be close in expendable mode; better than 4 tonnes anyway. I can't comment on your mass estimates, except that you seem to be neglecting the power and cooling systems (unless that's what the other five launches are for). And spacecraft design is generally more complicated than it seems at first; if I were the DoD I wouldn't trust a startup to so much as supply parts for a military satellite before it had a track record with other customers...

...

If I understand correctly, what you're proposing is mostly a ceramic resonator material with properties substantially superior to any existing material the military has access to in significant quantities, which you believe is the deciding factor in making the project you describe feasible. You must also believe you're much closer to being able to make this material industrially available than just "wouldn't it be cool if [numbers]?". Yes?

[GIThruster]

And spacecraft design is generally more complicated than it seems at first; if I were the DoD I wouldn't trust a startup to so much as supply parts for a military satellite before it had a track record with other customers.

I have no intention of building it. I'd want to partner with someone like Boeing and let them build it.

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[GIThruster]

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[GIThruster]

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