sevenperforce

I've thought about this before. Presuming that old Tony has figured out room-temperature superconductors, it's not terribly improbable to think that the "arc reactor" (which, I must point out, need not be a free energy device) can produce stupidly high voltage without significant thermal losses, voltage high enough to ionize air as a reaction mass and eject it using either magnetic fields (those silver pads could contain some sort of rotating magnetic field generator) or focused microwave sonic pulses. I hadn't heard the muon explanation, but that's not entirely unrealistic either. You can control effective muon lifetime by varying their speed. If the arc reactor can send muons through some sort of fiber-optic cable or superconducting magnetic channel (do muons have a magnetic moment?), then it can control (on a particle statistics basis, not on an individual basis) where those muons decay. A sufficiently intense stream of decaying muons would add a great deal of energy to air or even ionize the air, apart from the Cherenkov radiation. This could explain how he can appear to violate conservation of momentum (e.g., hitting someone with a ton of force while not appearing to physically move himself); he can fire a highly energetic but low-impulse beam of muons which then decay and release their energy into a much larger mass of air just in front of their target. Alternately, the muons can be timed to decay just outside the repulsor, producing a wave of ionized air that pushes against the repulsor to produce thrust. Because most people will go see a movie if it looks cool without caring about whether the science works?

Unless I woefully miss my guess, I'm pretty sure that you can see the shadow of the ISS on the trunk of the Dragon as it recedes...

I was replying to a comment where they were comparing the Martian downmass payload of the Dragon V2 to the transfer spacecraft launch mass of MSL on Atlas V 541. If you want to count the downmass only, then count the downmass only (899 kg for Curiosity vs ~4 tonnes in Red Dragon), but if you're counting the total mass into HMTO from the launch vehicle, count that. Otherwise you're very much apples-to-oranges. I think it's more about "look what we can do without incurring huge development costs for modifications" than "look at the maximum possible scientific payload we can put on Mars". Suppose I've built a revolutionary new ground effect hovercraft for sending heavy shipments across the Atlantic. If I decide to do a trans-Pacific flight just to show I can, it will be more impressive if I make fewer modifications to my vehicle. I can certainly see them stripping away a lot of the structural mass. Won't be quite as lightweight as a purpose-built Mars Bus but it will be improved. Like I said, it depends on how you're measuring. Are you look at percentage points, or orders of magnitude, or gross subtraction? And recall that if you count engine restart cycles rather than flights, it's closer to 0.3% vs 1% vs 100%. The posted prices are for a brand new rocket in a mission profile that allows a chance of partial reuse. The discount is applied when you elect to use recovered boosters. The central engine does four burns on RTLS flights: launch to MECO, boostback, re-entry, and landing. Plus two preflight test fires and an estimated average of four postflight test fires. Citation? Last I heard, Elon said that the side boosters could "probably" be recovered.

The JCSAT-14 booster has been lifted off of OCISLY and is currently being lowered onto the inspection stand at Port Canaveral.

Each SRB adds about $10 million to the ELV price, supposedly. The five-meter fairing used for MSL is also a touch pricier than the four-meter fairing. So we have $172.4 million as our total estimated vehicle price. I'm going to round up to $175 million to account for the increased cost of support on a Martian launch; I think that's conservative. The contract price for ISS deliveries is part of a long-term contractual arrangement and includes priority provisions for NASA. For example, SpaceX can carry multiple payloads in one ISS-delivery launch, but they have to give NASA priority and must scrap the secondary payload if NASA says to. Such a contractual price is not indicative of the price for a one-off mission like a Mars payload. And no, we don't add $62 million to the FH launch cost; the $90 million pricetag is the cost of all three boosters, plus the second stage, plus launch services and launch support. $90 million is the price for a Falcon Heavy launch regardless of whether they can recover the boosters. However, that's the price for a completely new launch vehicle. SpaceX will be reusing cores for the Red Dragon mission. A reused launch comes with a discount -- probably 30-40% for F9Ft. Let's say 30% to be conservative, and let's say that the center core is new, so only the side boosters (which will be recoverable for the Red Dragon mission) are reused. That's 18 of the 28 engines being re-launched (rather than 9 out of 10 engines as in a Falcon 9FT) so we will reduce that discount to 21%. The FH launch price can thus be estimated at $71.1 million, less than 41% of the Atlas V 541. "What about the capsule?" you say. Uh...what about it? The capsule is the payload for the launch vehicle. The 3.9 tonnes of Mars Science Laboratory wasn't the downmass to Mars; that was the launch mass of the entire transfer spacecraft: cruise stage, cruise propulsion system, battery and solar array, heat shield, EDL, and the Curiosity rover. The price of the spacecraft was not part of the Atlas V ELV. The dry mass of a Dragon V2 is nearly double the MSL mass, at 6.4 tonnes. Add 1400 kg of propellant and the claimed 4 tonne payload to Mars, and you have a launch payload mass of 11.8 tonnes. So on a price-per-kg basis, the Falcon Heavy's payload to Mars is 13% the price of an Atlas V payload to Mars. I'd say that's transformative. Oh, but wait...according to this source, NASA paid $215.1 million for launch services associated with MSL. So actually, that's 10.9% on a per-kg basis. But make no mistake... on a scale that is much closer to the spaceshuttle than airliners. That your formula 1 car only needs to be rebuilt every ten races instead of every race, does not make it into a streetcar. Again, it depends on how you look at it. 100% of SSME flights required a rebuild. Let us suppose that only 10% of Merlin flights require a rebuild, and 0.1% of airline engine flights require a rebuild. 10% is a lot close to 0.1% than it is to 100%, wouldn't you agree? Looking at it on a percentage basis means that as long as you have more than two flights between rebuilds, you're closer to the 0% point (infinite reusability) than the SSMEs. How accurate is that 0.1% number, anyway? The airline industry uses a metric called Time Between Overhaul, or TBO. This represents the runtime (usually given in standardized hours) before an engine needs to be removed, disassembled, and overhauled. For high-performance jet turbofan engines, the TBO is around 3,000 hours. Let's take an eight-hour transatlantic flight as an example. That means 375 flights between engine overhauls, or 0.27% of flights requiring a rebuild. Again, 10% is a lot closer to 0.27% than it is to 100%. Let's also take into account that restarts and shutdowns produce high stress on an engine. The SSMEs could not be restarted in flight and had to be refurbished after each test firing, and most airline engines only start and shutdown once per flight. The Merlin 1D, on the other hand, is usually test-fired twice before each launch, and the central engine fires up to four times per flight (for RTLS profiles). The CRS-8 booster will do ten test-fires before reuse, but let's say that eventually we'll be looking at closer to four test-fires before reuse. That means ten restart/shutdown cycles per flight. If they can manage the projected 10 launches before refurbishment, then we're looking at 100 cycles before refurbishment, or 1% of all cycles requiring a rebuild. 1% is within an order of magnitude of 0.27% and quite far from 100%. The central booster will probably not be reused on the Red Dragon shot, and they definitely will not land the FH core as a single piece. Rather than using crossfeed, the center booster will throttle down rapidly after launch to maintain closer to constant acceleration on the vehicle as a whole; this will leave it with a large fuel reserve at separation, but not so much that it has trouble maintaining acceleration.

You underestimate the desire for faux autonomy in individualists.

For anyone paying attention, S1 from JCSAT-14 is now visible on OCISLY via binoculars off Port Canaveral.

The way I heard it, the limiting factors were a combination of launch availability, launch price, and launch capability constraints. Particularly for smaller companies. The actual launch price itself may not be the majority of the investment, but launching itself represents such a large bottleneck in the whole process that it drives up costs all around it. Cheaper launch costs means that cheaper sats can be launched without as much fear of failure, and constellations in particular become far, far more economical.

Getting stuff into space is an end product which a lot of folks want. Slash launch prices by 50% and suddenly it makes sense to invest in a startup satellite service provider whose business model depends on several redundant comsats because now you can afford it. With lower-cost and more flexible launches, providers no longer have to overengineer their sats nearly so far, so those costs come down more. Lower costs make smaller companies competitive against the big giants, prices drop across the services market, and demand goes higher still.

Pretty lights!

Indeed. But if they can sell reused launches at a 30% markdown while increasing their profits, then maybe they end up doing twice as many launches the next year. And three times as many launches the year after that. And as prices continue to drop, demand goes up, and they get better at reuse, and prices drop further. So what if other companies start aping them? Lower cost, higher demand, more customers, repeat.

1/10 is target price with reuse. This is the guess, the part which has not yet been demonstrated. But you can absolutely be "significantly cheaper" without being 90% cheaper. Right now SpaceX is undercutting its competition by 20-40%. Not necessarily on a per-kg basis, but on a launch service basis. To be fair, JohnJACK was talking about the process, not the reuse numbers. The expected process of inspection, refueling, and reflying is much closer to airliner processes than to the rebuild-after-every-flight process of the Shuttle. But even if you go with reuse numbers, no one said it had to be a subtractive comparison. On a percentage basis, nine reuses before an engine rebuild is much closer to airline performance than zero reuses before an engine rebuild.

That SpaceX is significantly cheaper in regards to the competition is already established. That SpaceX's designs for reuse will bring costs low enough to meet Elon's goals? That's anybody's guess.

Well, BDBs only become cheap if economies of scale drive them, but SpaceX is already cheaper than its competition, so LV inventory flexibility (on the production side now, and presumably on the reuse side shortly) enables them to ramp up in step with economies of scale, rather than requiring high economies of scale from the outset.

Don't you mean Red Dragon? Anyway Elon said they'd most likely be able to recover the side cores from the Mars mission but not the center core.

Arguably, SpaceX has a major advantage over a BDB approach because they have more flexibility. Their rockets are already pretty cheap even at current economies of scale, so any reuse that isn't prohibitively expensive is basically a free lunch. A BDB approach requires full economies of scale from the get-go.

You seem to be defining "falsification" but that is not the same thing as "falsifiability". If someone broaches a theory which they claim is scientific, and I ask, "Is it falsifiable?" then what I'm wanting to hear is a specific prediction which, if shown to be false, would disprove their theory. If the theory is good and they're relatively clever, they should be able to come up with a suitable prediction. This ought to be something specific to their theory which I can go out and physically test. An obvious case would be Newton's law of universal gravitation. I ask Newton, "Is it falsifiable?" "Sure," answers Ike. "Find a massive body which exerteth not force in proportion to its mass, and my theory shall be disproven." So if someone claims that Intelligent Design is a valid scientific theory, I'll want to see them make a similar prediction. E.g., "Yeah, if intelligent design is true, you won't be able to find a genetic sequence with this particular set of attributes; if you find a genetic sequence with those attributes, then intelligent design is false."

What cantab said. The SOUND from the Merlin 1D, even at low thrust, would kill you. No doubt about it.

Minimum thrust is now just over 300 kN per Elon's discussion of the three-engine suicide burn on the JCSAT-14 mission. Being able to go from 2,268 kN to 302 kN (and everything in between) in a fraction of a second, controllably, is a pretty terrific achievement. That's the equivalent of throttling by 87%. I wonder what's harder on the bird: coming through re-entry at nearly a mile per second, or burning retrograde at 2.3 million Newtons to brake for landing.

Build a very large (30+ miles) coil gun in orbit. Give it a bunch of solar panels for power, and a flywheel or supercapacitor banks to store solar energy. Then, if you want to deorbit, let it fire you retrograde. If you want to orbit, on the other hand, take a high-altitude balloon to the edge of space and then hover on thrusters so as to intercept the front end of the coil gun. For landing itself...why not be a blimp?

I imagine it has to be. The rocket is supersonic when the landing burn begins. The maximum acceleration for a nearly-empty stage on a three-engine suicide burn is about 5 gees; subtract the 1 gee of gravity and you get just 4 gees or 39 m/s2. Six seconds of that will only earn you 235 m/s of dV, which is around 70% of the speed of sound.

Which they were. The one-engine landing burn was 90 seconds; this landing burn was 30 seconds. Assuming the same terminal velocity (which is close to accurate), that's just under 600 m/s of gravity drag saved.

"Classic" quantum entangled particles cannot be used for superluminal communication. Full stop. The characteristics which make them entangled ensure that there is no solution to the particle statistics that allows superluminal communication. However, if it is determined that the entanglement itself is carried by a faster-than-light particle with a non-zero energy, then it is possible that such particles could be used for FTL communication outside the realm of classic quantum entanglement. The reason I say nonzero energy is that a particle traveling faster than c actually has its greatest energy closest to c. Infinite speed corresponds to zero energy, which means it doesn't exist at all, and the mechanics of entanglement are not even analogous to those of gauge bosons. So you want a FTL particle with a non-infinite speed in order to have any hope of FTL communication.

Certainly, but I was asking about engine arrangements not multiple engines in general. LEO vs GTO.

Most cabins can survive a sufficiently small depressurization event, so you should make sure your crew can as well.