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Thursday, January 29, 2015

Show Low today

Will probably catch a movie when I visit my bank in Show Low today. Two front tires and an oil change are all I have left to prepare my truck for my pending trip. Also will extend my insurance for another six months which expires at the end of march.

Four weeks of abject poverty, then I hit the road.

I have a lot of places I hope to visit. A lot of people to see.

Mainly I will try to get my head focused. Life should not be so consistently miserable although I see no potential relief on the health front. Being alone is the worst of it. Not being around people will strangely provide some relief from that constant pressure.

They say misery loves company.  Company however, is disinclined to support the miserable. Understandably so. I have to go stick my head in the toilet now for the second time this night. Doctors are completely worthless.

After this trip I expect to come to terms with my situation. I will need to arrange some personal space. I have none at this time. Otherwise, there is no point in coming 'home.' Aren't I the cheery fellow?

Update: Both theaters in Show Low had American Sniper, didn't go to either. Got tires and oil change, so my truck is ready. Will get insurance next month so I have something left for this month. Now I wait.

Wednesday, January 28, 2015

Tuesday, January 27, 2015

The ultimate controller...

...is getting closer. Combine this with a 3d output and you'd never need to leave your head. Beware of brainhackers!

Sunday, January 25, 2015

Red lander

In CJ's last post (his best yet) he mentions 10 passenger mars landers. Does this fit within the parameters of the previous 4 passenger, 2500 kg payload landers? Easily.

Volume is no issue. If you've seen photos of existing Dragons it's obvious there is room for 10 for a short duration landing. Assuming each suited crew is 200 kg that leaves 500 kg of consumables. 50 kg each or about a week of supplies... enough to get them to a prepared surface habitat. They aren't going to stay in the lander any longer than they have to.

At $150m per lander which can bring more than 500 kg to the orbiting ship if needed that gives us a per crew cost from orbit to surface of $15m each. Add another $15m from earth to LEO and we only need an estimate for orbit to orbit (will update in a bit) to get total cost per crew.

$50m total sounds about right. About a third my former estimate.

[Update: 185 ton of fuel and supplies requires 3 FH or one BFR so let's call that $300m or $3m per crew. I'm going to stick with my $50m total per crew estimate.]

Saturday, January 24, 2015

BFR and MCT: Some thoughts on what they will look like, and be able to do.



BFR and MCT; some thoughts on what they may look like, and what they will be able to do.

There’s been much speculation on what SpaceX’s “BFR” (a non official designation meaning “big freaking rocket”, or other variants of the middle word). What’s known is it will use Raptor methlox staged combustion engines, and the design intent it to make it totally reusable. The specs on Raptor keep changing, and I highly doubt SpaceX will settle on a BFR design until the engine design is finalized (doing otherwise would be insane).

So, let’s work with what we’ve got; BFR will be big, and be reusable, and use Methlox. It will have a low cost per pound to orbit (or it won’t be built). It will also carry MCT (Mars Colonial Transport) to orbit on some missions.

Now lets get into the specs, and the first spec to look at is, of course, $$$. Developing BRF and Raptor will cost one heck of a lot. It’s been theorized that SpaceX will pay this out of pocket and use BFR for nothing but its own Mars launches. I consider this preposterous; we’re talking billions, and there’s no reason to do it that way, so why not save that money for other purposes? SpaceX has always optimized for cost.

BFR is planned to be a very large, fully reusable, system, and thus should have a very low cost per pound to LEO. I’ve long argued that they’ll offset R&D and construction costs the way they always have; by selling launches. Why wouldn’t they? The counter argument has always been that there’s no call for that much capacity, but SpaceX’s recent announcement of a 4025 satellite constellation, plus other companies being interested in such large constellations, blows that argument out of the water; there may well be, and soon, plenty of demand for a large low-cost-per-pound launcher. Selling such launches (or using them internally to launch revenue-generating sats) is IMHO how SpaceX will offset the R&D and construction costs of BFR. One result of this will be a far lower per-Mars-mission launch cost – because the infrastructure will already exist, and will have been paid for. (A current example of this dynamic; SpaceX is using paid-for expendable launches to develop its reusable F9R).

Now, this gets us to MCT, the Mars vehicle itself. SpaceX has released little but the name and payload capacity, so there has been much speculation. Much of the speculation claims that MCT will be able to go, on its own power, from LEO to a landing on the surface of Mars, and then (after tanking up ISRU) return from the Mars surface to Earth’s surface. The inherent problem with this concept is the rocket equation and the fuel fraction required. Building a craft able to land on Mars, as well as fly a reentry and land on Earth, requires one heck of a lot of dedicated mass (heatsheild, airo surfaces, landing engines for Mars, and above all structural strength). Let’s use a Boeing 747 airliner as an example; its cargo capacity (cargo version) maxes at 123 tons, within the ballpark for MCT’s claimed 100 tons payload capacity to Mars. The 747, bare bones empty (without fuel or cargo) masses 128 tons. So, one ton of cargo for roughly 1 ton of aircraft. Not too bad… but if you start adding things like heat shielding and life support, plus the heavier pressurized compartment needed for space, you’re increasing it by a lot.
For comparison, the Space Shuttle orbiter had a dry mass of 110 tons, and could loft 25 tons, a ratio of greater than 4 to 1 (and the Shuttle didn’t carry its primary fuel internally, so didn’t have the mass of the external fuel tank counted). So, let’s say that, via some magical engineering a liberal use of unobtainium as a structural element, you can get a better mass/payload ratio than Shuttle (with its tiny pressurized volume and no significant internal tankage) when scaled up to the size of a 747’s internal volume and cargo capacity. Let’s call it a 4-1 ratio.     

Where does that leave us with a postulated surface-surface MCT? It has to be able to land on Earth and on Mars, as well as have all the life support and other equipment needed for long-duration deep-space missions. Let’s be optimistic and assume the 4-1 ratio above, and we get 400 tons. But, we’re forgetting something; the fuel tanks. Shuttle didn’t include them in the airframe (except the small hypergolic supply) but airliners do (and doing so adds a lot of mass). The heat shielding shielding, and structure, has to protect the fuel tanks too, which means it’s huge, and thus heavy. However, we’ll be super optimistic and say the airframe can be enlarged to hold it all by simply adding 147 tons (If that sounds like a lot, it isn’t, as we’ll see in a bit). So, a surface-to-surface MCT with 100 tons of cargo masses, unfueled, at a very optimistic 647 tons. That’s our dry weight – everything but fuel.

There’s also the matter of internal pressurized volume. Again using an airliner as an example, the 747 has around 32,000 cubic feet – and so, for comparison, does ISS. ISS has a crew of 6, though could handle a few more. However, let’s use the 747 – ISS internal volume and assume it’d be enough for 100 people. (for comparison, the 747 carries 500, but does so in such cramped confines that a 6 hour flight in one is bad, and a 15 hour flight is unmitigated hell). Even if we postulate horrific crowding, you’d need at least that much volume (probably more) to accommodate 100 people for a months-long journey. However, we’ll assume the aforementioned magic engineering and say that a surface to surface MCT (which has to deal with reentry and landing on both earth and Mars, as well as long-duration deep space capability) will mass 647 tons.

So, let’s say you have your surface-to-surface MCT in LEO, and want to go to Mars. How much fuel do you need? Fortunately, that’s easy to figure out; the rocket equation. The optimal Trans Mars Injection burn (least delta/V, but a rare window) is 4.7 KPS. This assumes essentially zero propulsion for Mars orbital insertion (which can be done via aerobraking or multi pass aerocapture) and the landing itself. For the latter, we’ll be optimistic and say .3 kps (which is less than the F9R recovery profile, even without full boostback).  That gives us a needed delta/V of 5kps, so time to tank up! Calculating how much is easy; we’ll assume 380 ISP for Raptor Vac, the most likely engine choice. We already have our dry mass of 647 tons. The rocket equation gives a fuel requirement of 1833 tons (, but there are always boiloff losses, margins, etc, to consider, so add 10%, and we need 2016 tons of fuel. That gives us a fueled MCT mass in Leo of 2663 tons (about 3X the mass of ISS).


Now, how do we get a 647 ton MCT to Leo? This is what’s called, in engineering terms, a bit of a problem. BFR is going to need to be really, really, really big. A Saturn 5 could put 118 tons into LEO. However, MCT will take a performance hit due to reusability, so at best you’ll need a BFR significantly larger than a Saturn 5 just to equal a Saturn 5’s payload. But, our postulated MCT, unfueled, is 6 times the capability of a Saturn 5. A BFR that could launch it thus can’t be 3 cores, each the size of a Saturn 5. You’re going to need something massing 10 times the Saturn 5 – far larger than any estimate I’ve ever seen for BFR, and also beyond the realm of the plausible (either fiscally or physically).   

You’re also going to need the equivalent of 17 Saturn 5 launches just to fuel up one MCT. You’ll also need one hell of a lot of ISRU fuel production on Mars to refuel it once it gets there.    

All this begs the question; why do it that way and spend so much fuel boosting, for example, the earth-entry structures all the way to Mars and back? Or the Mars entry and landing systems all the way to Earth and back? Why not do it much more economically from every perspective, and do so in a way that gives you a far more versatile system? It’s the same problem that makes Orion such a pathetic design; you’re hauling along a huge mass because you’re treating your living space as the reentry vehicle. Far, far better to use a very small RV, like Soyuz’s, for the RV, and use a lightweight hab for the rest.

So, given the implausibility above of a surface-to-surface MCT, what might an optimized MCT-BFR system look like? MCT would not land on either earth or mars; it would be a space-only vehicle, thus saving enormous mass. A good example of such a craft would be a space station module; an inflatable one, such as Bigelow is building… let’s use their BA-330 design for a starting point. Once inflated, it’s big; 11,654 square feet internal volume (for comparison, ISS has 32,333, roughly akin to a 747) It’s a space station module, thus has life support, etc, included. Mass? 20 tons. It’s not big enough though… so you’d need more. Let’s assume 4 linked together. That gives you redundancy too, plus an internal volume of 46,616 square feet. Mass? 80 tons empty – which interestingly, is 4/5th the mass figure SpaceX gives for MCT- 100 tons empty. That’s also far more realistic an internal volume for 100 people, plus the needed life support equipment and consumables. It’s designed as a space station, so it has the ability, inherently, to exist in space long-term, no need to land. 

However- we need propulsion and fuel. So, add a 5th inflatable module, because inflatables would be ideal for fuel storage in space – why waste the mass needed for a rigid tank like the Shuttle ET? I’ll assume 20 tons (it’d be a lot lighter than a hab module, but it’d need a Raptor engine and thrust structure – perhaps two Raptors, for redundancy)

Okay, we have our 5-module MCT. Now, we need to get it to Mars. We’ll do the same rocket equation as above, and so our 200 ton (100 ton empty mass, plus 100 tons of cargo or humans plus supplies) MCT needs 565 tons of propellant to push it through TMI from LEO. However, this MCT doesn’t land on Earth or Mars, so there’s no reason to waste Delta-V by going deep into the gravity wells of Earth and Mars; high-energy orbits will be far better. Let’s use geosynchronous transfer orbit as an example for Earth, and a similar orbit for Mars. That has a major impact on the needed Delta/V. Instead of 5 kps propulsive ability (Leo to Mars landing, assuming aerobraking) we need 1.3 kps (assuming multipass airocapture into Mars GTO). Now, what does that do to our fuel requirement? It reduces it from 565 tons to 85 tons.  (Quite a big difference from the 2016 tons of fuel a surface-to-surface MCT would need to get from LEO to Mars! It’s reduced our fuel (all of it very expensive upmass) needed by 96%). We also save on margins by omitting the need to haul decent fuel (with resulting losses) all the way to Mars.

However, we still need to get to and from the surface of Mars. The surface-to-surface MCT could do it, but the space-only one can’t – it’s limited to orbit. Fortunately, the answer lies in the launch vehicle, the BFR; the reusable upper stage, to be exact. Any upper stage that can return from orbit to Earth is going to be light, about the density/volume ratio of an empty beer can. Thus, even in Mars’ very thin atmosphere, terminal velocity should be in the low supersonic range. That makes for an easy propulsive landing (it already has a heat shield, due to needing one to reenter on Earth). It already has landing legs, too. With some minor modifications (incorporated into the original design), it should be able to land on Mars, and carry a payload while doing so. Once on Mars, it can fuel up from ISRU, and function as a very capable SSTO – with at least the same payload as the full BFR’s max capacity from Earth – Mars’ far lower gravity, and thus orbital speed, makes SSTO easy.  The MCT would arrive in an eccentric (Basically, Martian GTO) Mars orbit, and be met by a BFR upper stage from the surface. If the stage had a payload shroud, cargo could be placed within it for the trip to the surface. A pressurized compartment would do the same for people, or, something akin to Red Dragons could function as landers (and then be returned to orbit by the BFR stage, which could loft more than enough to carry 100 people down – for a trip of less than an hour, 10 could fit in a Dragon).

So, a BFR upper stage, you have your needed Mars ascent/decent vehicle.

Now what about getting the MCT from Mars to Earth? Easier. The BFR stage brings fuel and cargo and/or passengers. You then need 1.1 kps, with multipass aerocapture (which does not require heat shielding) to get from Mars GTO to Earth, and brake into GTO at Earth. From there, high capacity (10 seat) Dragons could deliver any crew to earth, or a simple, small, orbital tug could transfer any cargo to LEO (again using areocapture). A likely cargo (seeing as how MCT would otherwise be coming back empty) would be fuel for the fuel depot in GTO, or one in LEO – it takes a lot less delta/v to get to Leo from the surface of Mars than it does from the surface or Earth. 

Given the low delta-V requirements from GTO to Martian GTO, you could add 1 KPS to do a fast transfer. (something else SpaceX has mentioned). This would also ease the launch window timeframe significantly (my calcs in this post are based on the once-in-2.2 years optimal Mars window).

Therefore, my hunch is that the MCT will either be, or be very similar to, four or five BA 330 modules. Going further, the four manned ones could be linked in pairs, separated by a tether, and spun up to generate artificial G. Generating Mars G would be even easier, as it’s 38% of Earth’s. This would acclimatize crew to Mars G en route, while avoiding the debilitating effects of prolonged weightlessness.  Also, artificial G will probably be required in order to get the breeding stock of food animals (which any Mars colony will have to have) to Mars. No need to take a whole flock of chickens or drove of pigs, for example, but you’ll need to take two or three plus a few hundred frozen embryos.

That brings us back to the BFR; how big does it need to be? For the space-only MCT, it really only has to get, at most, about 100 tons to GTO, which makes it about one and a half Saturn 5 class in capacity – well within the speculated range for the BFR. That’d also give its upper stage the capability (assuming ISRU refueling on Mars) to function as a Mars ascent/decent SSTO vehicle with 100 or more tons of payload.

As a further piece of evidence supporting my hunch that that’s what they have in mind for some BFR upper stages, SpaceX has said one of the reasons for choosing methane was the ability to obtain it via ISRU on Mars. So, unless part of the BFR is intended to go to Mars, that makes little sense (otherwise, only a surface-to-surface MCT would need Methlox, and could use smaller engines).

Using this architecture, the result would be a fairly low-cost, reusable multi-vehicle Mars transportation system. It would have cargo capacity in both directions, allowing for the Mars colony to export ISRU-derived commodities (Fuel, oxidizer, water, food) to Earth orbit (a good fiscal basis for an economically self-supporting colony), due to the fact that it takes far less propulsive delta-V to get from Mars surface to LEO than to do so from Earth.  Granted, there isn’t currently a demand, but the near future should see such a demand, in the form of several LEO and higher space stations, fuel depots, etc. (the advent of the cheap-per-pound launch capacity BFR promises would help create that market).  



Major caveat; I’m writing this post in the belief (If I’m in error, please correct me) that it contradicts nothing SpaceX has recently officially announced regarding BFR and MCT. I do however discount some SpaceX announcements from the more distant past, due to SpaceX's penchant for changing plans due to encountering physical and fiscal limitations during R&D. They have always done this. For example, their recovery method for F9R looks nothing like their announced parachute-based splashdown concept they tried with F9 1.0. Also, Falcon Heavy will look very different from the F9 1.0 based FH they originally announced. They’ve also changed the specs on Raptor massively, more than once. The only thing I’m accusing them of is having a sane approach to engineering, one that’s not needlessly bound by their past estimates. I consider this very commendable. However, it does means that outside speculators, such as myself, sometimes need to assume that some of SpaceX’s announcements may have a short shelf life. Thus, I’m taking such liberties in my speculation here.

A couple of definitions for terms used here; Aerobraking is using a partial entry to dissipate velocity and enter orbit (or set up for full entry). Aerocapture is multiple passes through the atmospheric fringes, such as MRO used to enter Mars orbit. Aerobraking requires a heat shield, while aerocapture does not. Both save on propulsive delta-V.

   



  

Export industry for Mars

A couple of posts below, Ken lays out a good argument for developing industry on Mars.

The only point I disagree with is the assumption that there's no market for exporting products from Mars.

An export industry is an industry, and there is, or soon will be, a very viable market; consumables.

Let's look at fuel depots in LEO for just one example; they're going to happen, and fairly soon. So, how does one get fuel to the fuel depot? Currently, plans are to launch it from Earth. This seems logical, because low earth orbit is only around 200 miles from Earth's surface. However, when it comes to spaceflight, the number that matters most is propulsive delta-V, not distance. To get to LEO, you have to accelerate your payload by around 9.2 kilometers per second (8 kps for orbital speed, and about 1.1 to 1.2 for gravity and aerodynamic losses).

Therefor, if you have a fuel depot for, say, methane and oxygen, or hydrogen and oxygen, getting it to LEO from Earth is a hard hill to climb. So, why not get it from Mars? That sounds preposterous because Mars is a long way from Leo, but that's in distance, not in Delta-V, and Delta-V is what counts.

Launching from the surface of Mars to low Martian orbit  takes 4.1 kps, a lot less than the 9.2 from Earth to Leo. But, how do you get from low Mars orbit to LEO? Part of that is propulsive Delta/v - 2.3 kps to get you on an earth-transfer trajectory. So, your total propulsive delta-V? 6.4 kps. From Earth transfer, you can aerocapture (no shielding required) into LEO. So, your fuel arrives in LEO having needed 6.4 kps propulsive Delta-V compared to 9.2 from Earth. That's quite a savings, but it's only a small part of the benefits. The rest is in launch architecture.

Take the F9 upper stage as an example. If you had it on the surface of Mars, not only could it do single stage to orbit with what, on earth, is its max payload, it could do Mars surface to earth transfer. (Falcon 9 stage sep occurs around mach 6, so 1.7 kps, and though the first stage has dealt with about half the gravity losses, the second stage has to supply around 6.8kps)

What this means in practice is that your Mars launch vehicle can be single stage to orbit - far, far cheaper and easier than staging, because it eliminates the need for the 90% of the vehicle you discard at staging (and even with reusability, this cost dynamic applies. a 747 and a Lear Jet are both reusable, but the 747 costs one hell of a lot more to buy and operate.)

With ISRU on Mars, you could easily produce methane and oxygen, launch them to low Mars orbit, where you use them to fill up a supercold transfer tank. (you avoid boil off losses by keeping the tank very, very cold, easy to do in space; you have a layer of aluminum foil a few feet from the tank, between it and the sun). Once the tanker is filled, a small rocket motor using some of that fuel boosts it through the trans-earth burn.

Hydrogen/oxygen is a bit trickier due to the temperature demands for Hydrogen, plus the tankage size needed. It's probably be more efficient to ship it as water, and electrolyze it as needed in earth orbit.

And speaking of water, that, too, is a commodity that'll be needed as space infrastructure grows. And that gets us to food, which is already a significant amount of upmass for ISS, and the demand for it will rise as we see more human occupation of LEO as well as further out.

So, given all of the above, we have an economic model for a major export industry on Mars. However, there's an even bigger economic factor, one that harks back to the birth of Transatlantic trade. The early colonies in North America were founded with people and supplies from Europe, and initially, the only value returned was that of the land in the New World. However, the ships delivering supplies were going back empty, and that's free cargo capacity, then as now. Back then, cash crops such as tobacco began to fill those empty holds. The same dynamic applies to a Mars colony; the vehicles delivering colonists and supplies to Mars will be going back to earth empty at first, so that's basically free cargo capacity. For a colony on Mars, you'll already have ISRU production of water, fuel, etc, and for vehicles like MCT, which is supposed to be reusable (and thus must return to earth), you'll have 100 tons cargo capacity to LEO. Whether MCT is able to land on Mars (I personally doubt it) of is a space-only craft, you'll have some kind of Mars-ascent system. The capability is inherent in the design concept of the raptor-powered heavy lifter; an upper stage of that reusable launch vehicle would have the inherent ability to land on Mars, refuel, and do either single stage to Mars orbit, or, single stage from Mars surface to Leo. So, to use the early transatlantic trade analogy, you'll already have the empty holds returning to Earth, so why not use them for an export industry?

Later, as the Mars colony's capabilities expand, if they're able to build pressurized habitats for Mars (they'll have to be able to do that) they can just as easily build them for space, and put them where they are needed for far, far less cost than launching them from earth. It might also be worth their while to build fuel depots (which are largely just large tanks), fill them in Mars orbit, and send them earthward - because one of the many advantages of launching from Mars is you're not limited by the diameter of the launch vehicle or payload shroud (restrictions imposed by earth's atmosphere). This of course applies to habitat design as well; if somebody wants, say, a 100 foot diameter sphere, or a segment of a large wheel, that's easy to launch from Mars but impossible from Earth, due to the atmosphere.