sevenperforce
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Posts posted by sevenperforce
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9 minutes ago, Mr Shifty said:
If you can imagine the X33 and a photon rasterizing your 1920x1080 monitor, the photon would complete an entire screen refresh while the X33 was about 1% done with just the first line.
Yeah, I'm gonna have to figure a way to cheat using perspective.
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Just now, Shpaget said:
This is the problem that's been bothering me for a few years. I always wanted to make a scale model of the solar system, but I can choose to depict either scale distances between planets and the Sun, or their relative sizes. Not both in the same model. Either the orbits would bee too big, or planets too small.
You can always have a nice little label that says "orbits to scale; planets displayed on a scale 10,000 times greater".
I'm thinking of doing a receding spiral...something like this:
Where perspective makes the spiral look like it is receding into the distance.
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21 minutes ago, Darnok said:
Maybe this will help http://joshworth.com/dev/pixelspace/pixelspace_solarsystem.html
Yeah, I love that illustration, but it doesn't fit so well in a single graphic.
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So I was trying to come up with a way to graphically represent the scale involved concerning the speed of light. I wanted to make a comparison between that speed (~300,000,000 m/s) and the fastest airbreathing craft in existence (the X-43 at roughly 3300 m/s). It's a pretty large gulf.
The simplest approach, I decided, would be to depict the distance traversed by a photon next to the distance traversed by the X-43 in some arbitrary period of time. Trouble is, the ratio is 90,333:1. That's a hard distance to depict in a simple graphic; I don't know of anybody with a screen large enough to display a 90,333 pixel line.
However, what about a spiral? If I could create a spiral with an arc length of 90,333 cm, then I could display it next to a 1-cm line. That would be a pretty striking way of depicting the difference. If an arc length of 90,333 cm was impossible, I could make a perceived arc length of 90,333 cm...for example, by depicting a spiral with 500 turns and an outer diameter of 180 cm (as if the diameter is constant but the spiral is receding back into the screen).
No idea how I could possibly find a way to render that, though. Any ideas? Or any other ideas of how to depict a scale difference of 90,333:1?
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13 hours ago, Jeb1969 said:
The movie San Andreas with Dwayne Johnson everything about that movie seemed scientifically inaccurate especially the tsunami. It felt like the directors flunked out of any sensible Geology, and or Seismology class.
The Winnebago outrunning the supersonic seismic wave...
...or was that 2012?
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42 minutes ago, Darnok said:
Today.
Many years ago we burned amount of fossil fuels with same ratio... orders of magnitude less than we could make any impact on atmosphere and today some people are saying about climate change and same people are saying that taking energy from Earth's core won't have harmful impact on Earth... that is really interesting opinion. The problem is that when we notice what is our impact on core it might be too late.
Do you have any appreciation of the difference between a quantifiable risk and an unquantifiable risk?
Geothermal heat is so many orders of magnitude greater than our baseline energy consumption that we cannot even alter the rate of heat transfer. We can only create channels to route the heat through generators as it goes past us.
1 hour ago, Sereneti said:Yes, tschernobyl and fukuschima was a good view about that
Yes, they were. Because the most massive nuclear accidents in history killed fewer people than coal kills every month.
You know that even if you include the casualties of Hiroshima and Nagasaki and Castle Bravo as victims of "nuclear power", nuclear power is STILL safer than any other energy source?
Thought experiment: If aliens arrived in Washington DC and offered to give the entire Earth free unlimited energy, with the warning that the flux from their energy source would kill ten humans randomly each day, would you take them up on it?
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59 minutes ago, Darnok said:
You know about Earth's magnetic field? Do you really think that making this field weaker is good idea?
How do you imagine that any human activity could have a measurable impact on the Earth's magnetic field? Our magnetic field regularly fluxes and reverses on energy scales that dwarf the entire cumulative energy consumption of humanity by orders of magnitude.
1 hour ago, Darnok said:As for bombs use one nuke in yellow stone park...
One nuke in Yellowstone Park wouldn't do a thing. You'd have to dig a massive shaft five miles deep, fill it with water so that it would transfer the shockwave more efficiently, and then lower a several-dozen-megaton nuke to the bottom. But after the dust cleared and all life was extinguished, Earth would continue to spin without any appreciable change in the amount of heat it generates.
56 minutes ago, PB666 said:
Gravity anomaly map of the Chicxulub impact structure.
To be fair, I assume Gaarst was talking about what you can see on an unmarked map of the surface topography...
28 minutes ago, Sereneti said:look: in Germany, they store nuklear waste on a Parking-space, - good planing`, caution?
They had lose some Ball.bearing-balls in a pump from a nuklear power-plant. And they had put the pump on again...
(and dont find the Ball-Bearing-balls ..., they are still in the Pump)
good Planing? Caution?at first they had do a "stress test" of the nuklear power plants...
at first all of the power-plants had failed...
then they reduced the level of the test, until all of the power-plants "survived"...
(they said "all of the power-plants had "survived"...)Caution?
As someone who works in certification and testing, an anecdote about "reducing the level of the stress test" really doesn't mean much to me. Those sorts of things are rather complicated.
Nuclear power is simply so much safer than any other energy source that it's stupid.
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7 hours ago, Sereneti said:
before i think about the long-therm-problems, there are enough short-therm problems to avoid that...
there is one city that have huge problems after geothermie...https://de.wikipedia.org/wiki/Hebungsrisse_in_Staufen_im_Breisgau
That sounds quite unpleasant, but it should be noted that this is a problem with poor civil engineering, not with overuse of a resource.
Globally, you cannot overuse geothermal. Locally, perhaps, but not globally.
7 hours ago, Sereneti said:Fosil-fuel is a good recource. But its used without thinking.
Nuklear-fuel is a good recource. But its used without thinking.
and so on...
if there is a "perpetum mobile", mankind will (ab)use it, too....
Nuclear fuel is not used without thinking. Quite the opposite. It is used sparingly, with a great deal of thought and planning and caution, and it is ignored and maligned without thinking. More education about nuclear power would lead to more use, not less use.
57 minutes ago, RizzoTheRat said:You should have patented the idea
One idea I still think would work well would be an inflatable wind tower that is vertical with a helical turbine. A really, really tall one (15+ km) under a combination of compression and tension. The power it generates allows you to electrolyze and pump in hydrogen gas at the base to replace diffusion losses.
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45 minutes ago, wumpus said:
The catch is that on worlds without an atmosphere, I can't see how a 50km+ coilgun is any easier to land on than a runway on an airless world. The benefits are that you can transmit the shock of landing onto the moon/planet while you have to design the 50km coilgun sufficiently rigid to handle the shock along the entire coilgun (all 50km need such robustness).
Well, you don't have to land on it. You just have to match orbit with it. It does the rest.
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40 minutes ago, SinBad said:
I thought up a reactionless drive. Basically a big reciprocating weight that moved forward quickly, transfered its momentum to the space craft, then drifted back ready to be driven forward again. Oh well.
Oh, that reminds me: I had a perpetual motion machine driven by buoyancy. Hydrogen or helium balloon that rises into the air, then uses a spring to compress a portion of the lifting gas, causing it to drop. Once on the ground, the compressed gas would be released, storing its energy in the spring, and lifting the balloon back up. I knew that the energy exchange between the spring and the gas could not be 100% efficient, but I figured I could make up the loss by taking energy from the upward and downward motion.
Took me forever to figure out that the gas would lose energy pushing against the higher atmospheric pressure at the surface...and that this pressure gradient was the only reason that the balloon moved at all.
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1 hour ago, Camacha said:
That does not chance the fact that we forcefully cool the Earth's core, however slight we might think it is. It is not a renewable resource.
Like Big Sky, or green house gasses, or any of those other supposed really big resources? Are we really that stupid, to make the exact same mistake yet again?
"...however slight we might think it is..."
Not really an issue of "think". We know how much geothermal energy exists, and its rate of escape into the atmosphere. We can calculate exactly the impact of temporarily diverting a fraction of that energy to power our civilization. It is stupidly below negligible.
Avoiding geothermal energy out of fear that we will deplete the Earth's internal heat is orders of magnitude sillier than thinking you can save gas mileage by clipping your fingernails shorter.
To the OP: I was full of perpetual motion machines, and their analogues. Magnets held tremendous promise. One was a "magnetic blocker" that blocked magnetic fields to let a ball roll down a slope, generating energy, then slid back out of place to let the magnet pull the ball back up the hill. When I learned that would definitely not work, I decided that I could simply put an electrical motor on one end to push the ball out of range of the magnet...not realizing that force x distance = work. Then there was the simple "generator powering a motor turning a generator" idea.
A slightly more refined one, when I was around 13 years old, was an electromagnetic Brownian ratchet to extract energy directly from heat. Violated the second law of thermodynamics but not the first (so I thought). Quite a nice setup, if I do say so myself.
When I was 16 I designed a battery-powered jet turbine engine for a motor vehicle that was supposed to run on water via electrolysis. Not a perpetual motion machine in any sense, of course, but still not viable.
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2 hours ago, wumpus said:
Are you really suggesting it is easier to build and land on a 50+ km orbital coilgun than to build a runway on the surface of a planet, especially with some sort of tailhook scheme similar to those used on aircraft carriers? I suppose you *could* use the coilgun to scavenge the energy from orbit, but the civilization capable of building such things is unlikely to need it (current US carrier design uses electric catapults. I strongly doubt anybody bothers scavenging electricity from the tailhook landings).
No, that's a way to deorbit, not a way to land or to orbit in the first place. Though I suppose you could use it for the latter purpose.
Its primary value would be for worlds without enough atmosphere for aerobraking.
Assuming you have autonomous asteroid mining or some other way to get a lot of raw materials in space, build a 30+ km platform in LEO with a gigantic coil gun in it. Set up solar panels and some sort of energy storage mechanism (flywheels or supercapacitors). When you want to deorbit your spacecraft, you simply load the spacecraft into one end of the coil gun and fire it retrograde, killing its orbital velocity. Far less propellant needed for the deorbit (or, in the alternative, a much easier shot at lithobraking or other landing methods).
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12 minutes ago, kunok said:
The problem is that it will be a lot more than just a 15%...
So?
If the Falcon Heavy is going to be required to begin with, then why worry about trying to minimize launch mass? It's not like they are going to save money on fuel or something.
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24 minutes ago, RainDreamer said:
Rendezvous with an orbital magnetic rail, have the rail slow you down using magnetic field in a spiral until you are slow enough to be captured and carry on the rail to the ground.
Hey, the question isn't asking for a reasonable/probable way.
Surprisingly, once you run the numbers it turns out that a 50+ km orbital coilgun is actually one of the more reasonable ways to kill orbital velocity, regardless of whether you have an atmosphere or not.
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10 minutes ago, Rakaydos said:
The question for SpaceX then would be if spaceX would save more with an R+D program for a dedicated mars lander and mass produce that, or simply mass produce their "proven" (after 2018) Red Dragon design.
In general, it seems R&D is expensive. If Red Dragon is "good enough", they might stick with it instead of going back to the drawing board.
This is the part that I keep coming back to. Development of a dedicated lander is NOT cheap...not even close.
If you're starting from scratch? Sure, in theory it is cheaper to develop, build, and test a dedicated Mars lander alone than it is to develop, build, and test a multiplanetary lander capable of dropping payloads on any terrestrial world. No question about it. But if your Earth lander that you ALREADY developed with NASA's money happens to be overengineered enough that it can serve as a passable Martian lander or a moon lander with only moderate modifications, then it is almost certain that those modifications will be vastly cheaper than developing a purpose-built lander for each target world.
If SpaceX can do a Mars mission or a moon landing or any other shot by modifying the lander they already have, it makes a lot of sense to prefer that approach over the development of a completely new spacecraft. Would a new spacecraft be more mass-efficient? Probably. Does a 15% mass-efficiency increase justify a 400% increase in development cost? I doubt it.
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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.
23 minutes ago, Razorstrike said:actually there is cuz if the no way of telling the suit's power then y would marvel make the movie
Because most people will go see a movie if it looks cool without caring about whether the science works?
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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...
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25 minutes ago, kunok said:
The capsule here is the transfer spacecraft, is not the part of the payload at all. It has no use after landing. And has a lot of disadvantages compared to a proper scientific probe. That's why some of us aren't hyped at all.
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.
28 minutes ago, kunok said:You know what i was expecting? I was expecting that they discard the idea of a red dragon capsule and made a "mars bus" derived from the dragon, based only in the heat-shield, and maybe the lower part of the structural frame. There is no use for the rest of the capsule, and will limit a lot the scientific capabilities.
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.
32 minutes ago, kunok said:The way i see is closer to 100% than to 0,1%, one is only a order of magnitude of difference the other is two.
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%.
13 minutes ago, fredinno said:SpaceX is making the cost estimate ASSUMING Booster reuse. It already accounts for it- why wouldn't they, the F9R is set to reuse a booster in a few months, and companies love to make biases to make themselves look better.
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.
15 minutes ago, fredinno said:In any case, the F9 actually does way more than 2 burns on launch- it's closer to 5-6.
Also, landing and launch puts more stress on a booster than static fire.
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.
17 minutes ago, fredinno said:Apparently the core can do a high-speed barge landing with the Red Dragon.
Citation? Last I heard, Elon said that the side boosters could "probably" be recovered.
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The JCSAT-14 booster has been lifted off of OCISLY and is currently being lowered onto the inspection stand at Port Canaveral.
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6 hours ago, 78stonewobble said:
Mars science laboratory is 3.893 kg to mars. It was launched on an atlas v 541. Meaning 1 common booster stage, 4 solid rocket boosters and a single engine centaur upper stage. We don't know the price of this...
However, the price of an atlas v 401, with no solid rocket boosters is supposedly $132.4 million, a number that includes "launch service, spacecraft processing, payload integration, tracking, data and telemetry, and other launch support requirements"... With 4 SRB's it will be even more expensive.
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.
6 hours ago, 78stonewobble said:SpaceX needs a Falcon heavy to send red dragon (4 tonnes?) to mars at the supposed Falcon heavy list prise of 90 million dollars. Add to that cost, that the center booster, will probably not be reused, essentially throwing away a falcon 9 and whether falcons numbers include "launch service, spacecraft processing, payload integration, tracking, data and telemetry, and other launch support requirements".
The list price of the falcon 9 FT is 62 million... but the contract price for nasa for deliveries to the ISS is $ 133 million, which does include cost of the capsule.
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So does the dragon capsule alone cost 71 million?
Is the 71 million price differential between a spacex list price and what nasa is paying also explaine by eg. "launch service, spacecraft processing, payload integration, tracking, data and telemetry, and other launch support requirements", not included in the list price?
Do we add 62 million or some other lower number to the falcon heavy launch costs, since we're throwing away a falcon 9 in the process?
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.
7 hours ago, 78stonewobble said:QuoteTo 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.
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%.
6 hours ago, PB666 said:Center booster is not fuel cross fed, it will be reused, they may land the three engine as 1 piece.
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.
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28 minutes ago, fredinno said:
Considering the world's increasing urbanization, it will only become more niche as time goes on.
You underestimate the desire for faux autonomy in individualists.
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For anyone paying attention, S1 from JCSAT-14 is now visible on OCISLY via binoculars off Port Canaveral.
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6 minutes ago, Kryten said:
It would not, because launch has never been a major factor in the overall price of communications satellites. Consider this; SkyPerfect JSAT are currently putting together the contracts for their next big mobile broadband sat, JCSAT 17. It will probably launch on a Falcon 9, with launch price probably somewhere below $65 million. They just signed a contract with Harris corp for $37 million for the antenna. Just the antenna. Take into account the money for upgraded ground stations, sat bus and transponders, and your launch cost is buried in the noise.
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.
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26 minutes ago, Kryten said:
Demand for space launches has never worked like that, because space launches aren't an end product that anybody wants.
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.
Call the insurance company
in Science & Spaceflight
Posted
How many seconds would the crew have to reach and don protective gear in the event of a moderate breach?