On Monday, April 3, 2017 at 6:18:53 AM UTC+12, JF Mezei wrote:
Questions:
1-If both boosters separate at same time, what sort of logistics are
involved in landing them, presumably at same time?
two barges a few km apart ? 2 landing pads on ground ? (at what distance?)
Apart from extra-terrestrial missions, what sort of commercial payloads
*need* this?
(1) Launching satellite constellations -
to capture the world's telecom market with direct broadcast two way satellites.
$1.7 trillion per year market (100x NASA budget)
http://www.patentlyapple.com/patentl...ps-beyond.html
(2) Launching solar power satellites -
to capture the world's energy market with energy beaming from space..
$3.5 trillion per year market (200x NASA budget)
https://dspace.mit.edu/openaccess-di...e/1721.1/57581
Capturing even a fraction of these revenue streams provides more than adequate funding for Musk to achieve his goal of making humanity a multi-planet species.
Or is this about launching multiple satellites at the same time?
53 tons is about a dozen powerful communications satellites
or
530 MW solar power satellite at 10 MW per metric ton.
Or is the goal to use the extra power to deposit second stage at a
higher GTO orbit so it has less work to do?
The weight tradeoff for more energetic orbits depends on the specific impulse of your kick stage.
The Falcon Heavy uses propellants that are generally more energetic than solid kick stages
Advanced communications satellites, and presumably newer solar power satellites will use solar
powered ion engines to maximise payloads to higher orbit.
https://www.extremetech.com/extreme/...ines-is-online
But if stage 2 starts at 28° inclination but at higher altitude, doesn't
it make it harder for it to correct inclination to 0° equatorial? Or is
that a minimal concern?
Depends on details. Generally speaking a lower orbit involves a higher delta vee for a given plane change. That's why you boost to a higher orbit, and then do the plane change, if required.
If you are at a 28degree latitude, your minimum inclination at launch is 28 degrees. However, you can launch into a higher inclination orbit. So, if you want to do a sun synchronous polar orbit , you don't need to do any plane change.
(Or is it expected the 1st stage will make a large contribution to
reduce inclination)
Its a trade off of propellant weight versus payload weight. If you add hardware like a separate kick stage, you have to include structure weight. There are other factors as well, but this is the primary one.
The Falcon Heavy Payload User's Guide isn't easily available on line. However, the Falcon 9 Payload User's Guide is! This gives you a detailed look at how you can configure your rocket to achieve the mission you have for it - and the trade offs you will make
http://www.spacex.com/sites/spacex/f...de_rev_2.0.pdf
* * *
SpaceX could continue the excitement, especially if Musk arranges to capture a even a small portion of the energy and telecom markets.
Reinvesting a portion of the funds earned by delivering energy and data to Earth, into advanced propulsion will build bigger hotter rockets going forward. The same satellite hardware that delivers data and power on earth, could be redesigned to service Mars, or the Moon, and the asteroid belt, and beyond.
Power satellites also do double duty powering deep space propulsion systems, without the need of a large solar collector or nuclear power source on the deep space system itself. This is a vast improvement over the chemical kick stage.
For example, a 500 megawatt solar power satellite that uses microwaves, could beam energy to an energetic deep space stage that produces 1.9 metric tons of thrust whilst sustaining a 54 km/sec exhaust speed. At 1/30th gee a 53 ton payload is boosted to Mars in 2.2 hours.
Such a deep space stage is quite capable, and delivers a very large fraction of the orbital payload to its destination. An automated high energy stage like this would also be highly reusable because of short cycle times of less than a day are possible.
For example, a chemical booster is is just about equal a payload to Mars, kicks that payload into a transfer orbit.
An energetic maser powered ion rocket could be as small as 1/10th the size of the chemical booster. (see calculations below)
The chemical booster is limited in its energy, so to recover it, requires that once the payload is on track for Mars, small changes in the chemical boosters course to come back to Earth precisely two years later. So, that it intercepts Earth slows and lands for reuse. Which is just in time for another minimum energy transfer to Mars, which has a 2.15 year synodic period.
But that means the chemical booster spends 2 years in space, and can be used only a handful of times over its life, amortising its cost over fewer flights makes it more costly.
The maser/ion stage considered here powered by a commercial solar power satellite, as an alternative to the chemical booster, is small enough and energetic enough, so that it could slow down after boosting the Mars payload, and return to start position in a matter of hours. Allowing hundreds of times more flights, amortising over more flights, lowers costs by that factor. Reducing the number of launches to support the kick stage, also reduces costs by the same factor.
Calculations
Lox/Methane Booster - with 50% propellant fraction;
Vf = Ve * LN(1/(1-u)) = 3.8 * LN( 1/(1-0.5)) = 2.63 km/sec delta vee
Maser/Ion Booster - with same delta vee
u = 1 - 1 / EXP( 2.63 / 54.00 ) = 0.0476
about 5% - or 1/10th the weight of the chemical booster. That is 53 tons of propellant in the chemical booster is replaced by 5.3 tons of propellant in the ion booster.
Now, if the structure plus recovery propellant of the maser powered ion stage is the same as the chemical stage, say 4.7 tons - to adjust the speed of the empty chemical booster by 0.8 km/sec to place it on a recovery path - requires 0.9 tons of propellant for the chemical stage- leaving 3.8 tons for structure for the chemical booster.
And, to adjust the empty ion booster by 5.3 km/sec - which basically stops the stage and reverses its direction after releasing the 53 ton payload toward Mars- requires only 9.3% or 0.44 tons for a 4.7 ton stage weight - due to its higher exhaust speed - leaving 4.26 tons for structure.
So, launching a 53 ton propellant tank for the ion booster from which a ion kick stage refuels many times, and kick 10 Mars bound payloads to the red planet, with each fuelling flight, whereas the chemical booster kicks only 1 payload every fuel launch.
The hardware is used far more many times and
can put larger payloads into a variety of orbits.
A power satellite network and a communications satellite network around Mars based on the hardware developed for Earth, extends the demand for power and data off world.
It can also be used to power energetic stages to capture and slow incoming payloads, and return those payloads efficiently to Earth, or even send them further into space,
Of course, if powerful gigawatt scale laser beams or maser beams are used to energise rocket on Earth, or on the Surface of Mars, or Venus, reusable single stage stages quite different from the type we are used to that use chemical propellants, become possible.
This not only continues the decline in space launch costs, but also expands the use of space launch going forward. Ballistic transport from point to point on Earth will displace air travel and all other forms of travel going forward, and make access to space seamless, while increasing the demand for energy as the wealth of the world increases as well.