Author: Adam

SpaceX to Mars?

SpaceX has answered the skeptics recently with a frank discussion of its costs thus far in its May 4, 2011 Update. An excerpt of relevance is this…

WHY THE US CAN BEAT CHINA: THE FACTS ABOUT SPACEX COSTS

The Falcon 9 launch vehicle was developed from a blank sheet to first launch in four and half years for just over $300 million. The Falcon 9 is an EELV class vehicle that generates roughly one million pounds of thrust (four times the maximum thrust of a Boeing 747) and carries more payload to orbit than a Delta IV Medium.

The Dragon spacecraft was developed from a blank sheet to the first demonstration flight in just over four years for about $300 million. Last year, SpaceX became the first private company, in partnership with NASA, to successfully orbit and recover a spacecraft. The spacecraft and the Falcon 9 rocket that carried it were designed, manufactured and launched by American workers for an American company. The Falcon 9/Dragon system, with the addition of a launch escape system, seats and upgraded life support, can carry seven astronauts to orbit, more than double the capacity of the Russian Soyuz, but at less than a third of the price per seat.

Note the cost of developing the “Dragon” which is the first private aerospace vehicle proven capable of return from orbit. About $300 million, with a dry mass of about ~4.2 tons, thus ~$72 million/ton to develop. To develop large Mars mission vehicles might be assumed to cost similar amounts per ton of aerospace machinery. But can it be done even cheaper?

The Mars Society has made an impassioned plea to President Obama to consider a minimalistic Mars Mission concept based on the Falcon Heavy and Dragon space-vehicle…

The SpaceX’s Falcon-9 Heavy rocket will have a launch capacity of 53 metric tons to low Earth orbit. This means that if a conventional hydrogen-oxygen chemical rocket upper stage were added, it would have the capability of sending 17.5 tons on a trajectory to Mars, placing 14 tons in Mars orbit, or landing 11 tons on the Martian surface.

The company has also developed and is in the process of demonstrating a crew capsule, known as the Dragon, which has a mass of about eight tons. While its current intended mission is to ferry up to seven astronauts to the International Space Station, the Dragon’s heat shield system is capable of withstanding re-entry from interplanetary trajectories, not just from Earth orbit. It’s rather small for an interplanetary spaceship, but it is designed for multiyear life, and it should be spacious enough for a crew of two astronauts who have the right stuff.

Thus a Mars mission could be accomplished utilizing three Falcon-9 Heavy launches. One would deliver to Mars orbit an unmanned Dragon capsule with a kerosene/oxygen chemical rocket stage of sufficient power to drive it back to Earth. This is the Earth Return Vehicle.

A second launch will deliver to the Martian surface an 11-ton payload consisting of a two-ton Mars Ascent Vehicle employing a single methane/oxygen rocket propulsion stage, a small automated chemical reactor system, three tons of surface exploration gear, and a 10-kilowatt power supply, which could be either nuclear or solar.

The Mars Ascent Vehicle would carry 2.6 tons of methane in its propellant tanks, but not the nine tons of liquid oxygen required to burn it. Instead, the oxygen could be made over a 500-day period by using the chemical reactor to break down the carbon dioxide that composes 95% of the Martian atmosphere.

Using technology to generate oxygen rather than transporting it saves a great deal of mass. It also provides copious power and unlimited oxygen to the crew once they arrive.

Once these elements are in place, the third launch would occur, which would send a Dragon capsule with a crew of two astronauts on a direct trajectory to Mars. The capsule would carry 2500 kilograms of consumables—sufficient, if water and oxygen recycling systems are employed, to support the two-person crew for up to three years. Given the available payload capacity, a light ground vehicle and several hundred kilograms of science instruments could be taken along as well.

The crew would reach Mars in six months and land their Dragon capsule near the Mars Ascent Vehicle. They would spend the next year and a half exploring.

Using their ground vehicle for mobility and the Dragon as their home and laboratory, they could search the Martian surface for fossil evidence of past life that may have existed in the past when the Red Planet featured standing bodies of liquid water. They also could set up drilling rigs to bring up samples of subsurface water, within which native microbial life may yet persist to this day. If they find either, it will prove that life is not unique to the Earth, answering a question that thinking men and women have wondered upon for millennia.

At the end of their 18-month surface stay, the crew would transfer to the Mars Ascent Vehicle, take off, and rendezvous with the Earth Return Vehicle in orbit. This craft would then take them on a six-month flight back to Earth, whereupon it would enter the atmosphere and splash down to an ocean landing.

Spending ~2.5 years in a Dragon capsule will take a couple of claustrophiles, but people have endured in remarkably nasty conditions. So why not? It’s daring, but is it necessary?

Zubrin asks for a cryogenic upper-stage to throw the Mars vehicles to Mars, but is that really needed? Can better performance be achieved by using a slightly different approach? In a previous post I outlined the Falcon Heavy Tanker (FHT) – essentially a Falcon Heavy Stage 2 with a stretched tank and a docking collar for coupling to a Dragon. I estimated 55 tonnes of RP-1/LOX could be placed in orbit and a FHT dry-mass of 2.5 tonnes. To get to Mars takes ~3.7 km/s from LEO, the so-called Trans-Mars Insertion (TMI) delta-vee, thus with a vacuum Isp = 342s, that means the Falcon Heavy Tanker can push 27.2 tonnes into a TMI orbit, thus a net payload of ~24.7 tonnes. With aerobraking that’s considerably more than the Mars Society’s quoted payloads, providing somewhat better living conditions for the explorers.

Of course the payloads need to be orbitted separate to the FHTs, but at less than half the Falcon Heavy’s usual 53 tonne payload, that means 2 separate Mars payloads can be orbitted by one vehicle, and supported by a separately orbitted crew in a Dragon. Potentially we can reduce the FHTs to just three to support a beefier Mars Semi-Direct mission which doesn’t mean living in a Dragon capsule for 2.5 years! Alternatively we launch the Mars Ascent Vehicle directly via a single Falcon Heavy, as per the Mars Society plan, and launch the Mars-bound Habitat and Earth Return Vehicles via 2 FHT launches and 1 Falcon Heavy. Four Falcon Heavy launches versus 3, but delivering more payload.

Zubrin is, I suspect, hoping to minimize the cost of developing new systems, thus using two Dragons and only needing to develop a low-mass Mars Ascent Vehicle. However the current Dragon probably can’t be used as a Habitat for +2 years with some development work, thus the difference between the two approaches is probably negligible. I appreciate his gumption and burning desire to get a finger-hold on Mars as soon as possible, but I’d like to see the developed systems able to do more than a stunt.

Go SpaceX! Go Mars-Soc!

Black Holes older than Time?

Two recent arXiv preprints combined make for an interesting idea. Here’s the most recent Science headline maker…

Some black holes may be older than time

…which handily has the arXiv link…

Persistence of black holes through a cosmological bounce

…Carr & Coley pose the idea that some black holes get through a cosmological Bounce (a Crunchy Big Bounce) relatively unscathed. George Zebrowski used something like that idea in his “Macrolife” novel (1979), in which Intelligent life from previous Big Crunchy Bounces survived in the Cosmic Ergosphere. Poul Anderson did it earlier in “Tau Zero” (1970), but the problem with both is that the mass of the Universe, even if it has a net spin, probably won’t form a black-hole style ergosphere when it contracts inside its own event horizon. The topology is all wrong for regular cosmology and it’s doubtful whether a white-hole style cosmos expanding in a precosmic void would ever go Big Crunch. However they might’ve been partly right, thanks to this intriguing preprint…

Is There Life Inside Black Holes?

…in which Vyacheslav I. Dokuchaev speculates that Life might orbit within supermassive black hole event horizons because it can and it might use the emissions of the Cauchy Horizon and massive time dilation for technological purposes. If Life can live inside a Black Hole, and Black Holes can survive the Crunchy Big Bounce, then might not Life survive too? Or am I speculating over a data-void on too many planks of inference? Perhaps only a dive into a Black Hole will ever tell us for sure, though whether we can ever send the news home is debatable. According to Igor Novikov we might be able to access the regions inside via a wormhole specifically dropped in…

Developments in General Relativity: Black Hole Singularity and Beyond

…which might provide a means to reach the aliens inside from past Cosmic Cycles. Perhaps that’s exactly what they want or are hoping for. Of course such vastly old entities – if they’ve survived – might be so utterly foreign to us cosmic youths that we might be unwittingly unleashing “Elder Gods” of Lovecraftian style moral indifference. Or perhaps we’d find them to be akin because of the daring that sent them across the Event Horizon in the first place? Cosmic Extreme Sports, anyone?

[found Under a Gibbous Moon]

Hydrogen Greenhouse Worlds…

The first planets to form probably attracted a primary atmosphere of H/He from the solar Nebula. In our Solar System these were driven off from the four Inner Planets and retained by the Outer Giants, but in theory smaller planets can retain such a mixture. I’ve speculated about such worlds on these blog pages before and now there’s a new arXiv piece discussing the greenhouse abilities of H/He…

Hydrogen Greenhouse Planets Beyond the Habitable Zone

…the summary conclusion being that 40 bars of H2 can keep the surface at 280 K out to 10 AU around a G type star and 1.5 AU around an M star. Thus planets with oceans of water can exist at Saturn-like orbital distances given enough primary atmosphere. Super-Earths are the most likely to retain their H/He primary atmospheres due to their higher gravity, as young stars put out a LOT of EUV light which energizes the hydrogen and strips it away in a billion years or so, if the planet is too close. Out past ~2 AU for a G-star and that effect isn’t so dramatic, thus a Super-Earth where the Asteroid Belt is today would’ve retained its primary atmosphere and probably be warm & wet.

Such a “habitable planet” is only barely defineable as habitable because it has liquid water, but is unlikely to remain warm/wet habitable if the hydrogen is exploited/depleted by methanogens making methane out of it with carbon dioxide, nor oxygenic photosynthesisers making O2, via CO2+H2O->CH2O+O2, which then reacts rapidly with hydrogen. Could another kind of photosynthesis evolve to restore the hydrogen lost? Hydrogen makers exist on Earth, so it’s not unknown in biochemical terms, but I wonder what other compound they need to release net hydrogen from methane/sugars/water?

Mars – the New World!

Mars is SpaceX CEO Elon Musk’s stated goal in space…

SpaceX aims to put man on Mars in 10-20 years

…though the “10-20 years” is how long developing the means to get there will take, not a firm time-line from Now. Robert Zubrin made similar time-scale remarks ever since he began publicising his Mars Direct architecture in 1990/91. I think SpaceX needs to prove the safety of its “Dragon” manned vehicles and the reliability of its Falcon Heavy before it can embark on flying people to Mars. But, as explored here in a recent post, the Falcon Heavy can send payloads sufficiently heavy to Mars to support both Mars Direct (NB: different link, more details) and Mars Semi-Direct architectures. What’s not currently available is low-mass, high-power nuclear power-sources sufficient to support either architecture – the Earth Return Vehicle (ERV) of Mars Direct and Mars Ascent Vehicle of Mars Semi-Direct both make fuel from the atmosphere via a process powered by a small reactor.

Could we do without the nukes? Mars Society Australia certainly thought so when they designed a non-nuclear version, using conservative solar-power specific-power assumptions…

Mars Oz – Mars Semi-Direct Solar

…which might be overly conservative as that’s a decade old solar-tech being assumed. I suspect more power for the same mass assumed will be available and so the outlook is even better than they assumed.

Once we’re there what can we do to improve the place? Apparently Mars is already undergoing changes of its own accord…

Dramatic changes in Mars’ atmosphere found

…the possible extra ~80% of atmosphere would help, but the surface pressure would still only be 10-12 mb (and about ~20 mb at the bottom of Hellas Planitia) which isn’t habitable, but is enough make Mars a nicer place for some lifeforms.


Beyond the Moon via Falcon Heavy

For serious interplanetary operations we need fusion propulsion – plain nukes aren’t much better than chemical rockets performance wise. Outer Planet access with trip times under a year are probably vital on biomedical grounds due to the nastiness of high-energy Cosmic-rays. Thus the necessity of fusion propulsion.

But before we shoot off to Jupiter, what can we do about Mars and a little bit beyond?

Assume three FH Tankers (52 tonnes fuel, 3 tonnes dry-mass) and a payload massing 55 tonnes. Arrange two Tankers as First Stage and one as the Second Stage to push the payload. What delta-vee do we get? Over-all mass ratio is (220/(220-104))*(110/(110-52)) = 3.6, thus with the Merlin Vacuum engine we get 1.28 x 342s x 9.80665 = 4,293 m/s – enough to put our cargo on a Hohmann transfer to Mars, with a bit of a reserve.

For unmanned vehicles carrying cargo the 258 day Hohmann orbit is preferrable, but punitive for a manned mission. With a bit of extra delta-vee – such as the above figure – a manned mission can save on supplies and cosmic-ray exposure. Gerald Nordley discusses the issue in his on-line essay…

Going to Mars?

…indicating trip-times of 130-180 days are reasonably feasible. Thus crew can travel quicker than freight. The canonical Mars Semi-Direct would require delivery to Mars of a Habitat, and Earth Return Vehicle and a Mars Ascent Vehicle, all in the roughly 55-60 tonne mass range. Thus a total of 12 Falcon Heavy launches to deliver a crew of six to Mars. A launch cost of just $1.5 billion for a Mars mission is a dream! But eminently practical with Falcon Heavies available.

Going to Mars lets us save propellant via aerobraking – aerocapture into a highly elliptical Mars orbit – which isn’t available if we go beyond Mars to the Asteroid Belt. Trip-times rapidly go up as we move further away from the Sun, especially for tricky fuel-saving orbits with higher aphelia than the destination. Another speed-bump is the non-zero inclinations of the asteroids, which makes them even trickier to reach.

So what do we do? Personally I think this is where we have to start getting out of the rocket straight-jacket and start getting serious about solar-sails – as recently successfully demonstrated by IKAROS and Nanosail-D. There’s a certain elegance – and zero-fuel budget – which has an immense appeal.

Sunlight to electricity – direct!

Solar power without solar cells: A hidden magnetic effect of light could make it possible

(PhysOrg.com) — A dramatic and surprising magnetic effect of light discovered by University of Michigan researchers could lead to solar power without traditional semiconductor-based solar cells.

…of course the efficiency is currently below 10%, but improvements are likely. The problem with solar isn’t turning it into useful energy, but storing it! If you could do that easily and cheaply, then you can change the world.

Falcon Heavy to the Moon! – Part 2

In my last post I discussed the Falcon Heavy (FH), which SpaceX is planning to use to launch payloads into LEO of up to 53 tonnes. I suggested modifying the design slightly, so it can carry that same mass, or a bit more, to LEO as propellant in its tanks. Such a FH Tanker can then be mated to various payloads and send them to the Moon, via the Earth-Moon Lagrange-1 (EML-1) point.

But how much payload? Assuming the vacuum version of the Merlin rocket engine being used in the Falcon 9 and FH, and its vacuum Isp of 342 seconds, that allows reasonable delta-vees for decent payloads.

If we assume the total fuelled mass of the FH Tanker is 56 tonnes, and 53 tonnes of that is fuel, then 22.5 tonnes of payload can be delivered to EML-1. However the FH Tanker arrives empty. While it might be cannibalised for its large pressure volume, cluttering up the EML-1 is probably short-sighted. Also SpaceX is committed to making mostly reusable rockets, so we might have to return the FH Tanker to LEO. That requires it to arrive at EML-1 with 6.232 tonnes of propellant still in its tank, reducing the payload to just 13.25 tonnes. Tweaking the mass of the FH Tanker means we might manage it for ~2.5 tonnes dry mass and ~15 tonnes can then be delivered.

Interesting the Project Apollo’s Lunar Excursion Module, which successfully landed 12 men on the Moon over 6 missions, massed just 15 tonnes. It used a lower performing fuel combination and thus a modified version using the LOX/RP-1 of the Merlin might deliver an LEM to the Moon and back with more payload allowing weeks of stay-time. Alternatively a larger lander could touch down using 22.5 tonnes of propellant delivered by an FH Tanker. The first option requires two launches, one an FH Tanker and the other to deliver the Lunar Lander to LEO. Alternatively two FH Tankers might combine in LEO to push a larger load to the EML-1, requiring 3 launches in total.

Assuming a linear scaling, a bigger LEM with 6 passengers might mass ~45 tonnes, requiring two full payload deliveries to EML-1 and four launches to LEO. All this could cost ~$1 billion ($1 Gigadollars or $1G) – four FHs at $0.125G each and $0.5G for the Heavy LEM. That’s half the “Apollo” programme’s achievement delivered to the Moon for a tiny fraction of its $30G budget (in 1969$.) What’s more with modern inflatable space-habitat technology we’re talking about a relatively large Base being landed, not a mere two-man “sky-car”. With touch-down near one of the Lunar Cold-traps and access to the ice there, plus solar-power, then the 6-person crew could conceivably stay for months, setting up a semi-permanent Base. For a full $30G budget – worth roughly ~1/5 of what it was in 1969 – some 180 people can visit the Moon, stay six-months each and thus spend ~90 person-years exploring and expanding the Base. If anything is worth doing on the Moon, then such an effort will go a long way towards determining what it might be and if it can turn a profit. Platinum-group metals recovered from meteorites? Exotic minerals? Fusion fuels? Unimaginable breakthroughs?

We won’t know unless we go and stay for bit longer than the ~fortnight spent on the Moon by all the “Apollo” missions.

NB: I haven’t discussed how the astronauts get to EML-1 and back to LEO/Earth. The Lunar Landers are assumed to launch their Ascent Stages back to EML-1, which isn’t much different to going into Low Lunar Orbit like the “Apollo” LEM AS did. But a refuelable LEM system is preferable once an actual Base is operating and extracting propellant from the Moon. This should be factored into Base planning and begun as soon as possible so more payload can actually be delivered to the Moon. Launching 7 astronauts to EML-1 in a fully loaded Dragon Capsule, using the FH Tanker system described is incredibly easy. And Dragon is designed with a heat shield sufficient for Earth-Moon return. A six-person ferry, with minimal life-support, for delivering crew to the Base will probably mass a lot less than the 45 tonne Lunar Lander outlined above.

Falcon Heavy to the Moon!

Interesting design. With a slight modification a Falcon Heavy can orbit ~55 tons of propellant. Then a fully loaded Dragon Capsule can dock with it and use it to launch into a Lunar, or Halo, Orbit. A landing vehicle, preplaced in Low Lunar Orbit, or the Earth-Moon L-1 Point, can then finish the journey. All without using a gargantuan booster. At ~$100 million per launcher, plus another $100 million for the lander, and a Moon mission can be done for ~$500 million. A steal compared to the multi-billions of the Ares V program that the USA had committed to under GWB. A properly designed lander can then be kept at the ready for repeat missions, tanked up as required.

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