SpaceX News

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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Skipjack
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Re: SpaceX News

Post by Skipjack »

happyjack27 wrote:...updated my spreadsheet:

a "heavy" configuration (2 additional boosters) would weight about twice as much and deliver a little over twice the fuel in one launch.

(why not 3x? because you still only have 1 tanker)

so half as many launches, and half as many uses of the tanker (though 3/2 as many uses of the boosters)

the middle booster won't reach leo, so won't need to do a de-orbit burn. will be going a little over twice as fast than the side boosters where when it decouples.

presumably the middle booster engine configuration could be optimized (less thrust needed and spends more time in high altitude) to reduce mass and increase isp a little.
Reusing the center booster in a 3 booster configuration would be a challenge. The center booster would be too far down range to fly back to the launch site. It would have to land on a gigantic barge downrange. I think that would not be every cost effective.
Personally, I would rather go the opposite way and make a reusable SSTO based on the tanker stage alone (without the booster). According to Musk a stock tanker could be an SSTO without a payload and might have trouble coming back (though he might not have thought that part through all the way).
You would use slightly shorter bells for the vac Raptor engines. That saves weight and allows them to contribute more at SL with still a good Isp all the way to orbit. The tanker would need relatively heavy structure to transport the fuel all the way to orbit. Some of this could be optimized for it just being a payload shroud/adapter.
An SSTO would need less fuel for the return to the launch site than the booster does. The booster needs 7% fuel reserves for RTLS and landing.
The SSTO would only need to do a deorbit burn, a re- entry burn and a landing burn. This would be the equivalent of the fuel needed for a barge landing. Conservative estimates put it at 2%, though it might be less.
Conservative estimates with all these considerations give it the same payload as the Falcon 9 1.1, which is enough to launch a Dragon v2 with trunk or the equivalent into LEO. Musk indicated that the payload of the ITS would improve over time as the system gets optimized. So it would be likely that over time this SSTO could be optimized to have the same payload as F9 FT, maybe even more. According to Musk, a tanker can be reused 100 times and costs 130 million to build. That is 1.3 million per launch. Musks estimated maintenance, payload and launch site cost for the entire stack of tanker and booster would put the total cost of a lauch at 2.4 million. That would most likely be even lower for the SSTO RLV. Even if it was 10 million, it would be way lower than the current cost of an F9 launch. With 10 million you could launch two of them (one to refuel the other) for launches to GTO and beyond and still be cheaper than F9.

happyjack27
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Re: SpaceX News

Post by happyjack27 »

SpaceX lists the price of a falcon heavy launch at a little more than 50% more than that of a falcon 9 launch.

so with a heavy configuration for the tanker, that's 1.5x the cost, half the time, which translates to 75% of the cost - a 25% savings.

this is in addition to twice the longevity of the tankers (half as many uses needed), and 3/2 the longevity of the boosters.

Image

happyjack27
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Re: SpaceX News

Post by happyjack27 »

running the numbers from: https://en.wikipedia.org/wiki/Interplan ... ystem#Cost (cost per launch for each vehicle)

a heavy version would deliver a little under twice the fuel, but launch cost would be a little over double.

so it doesn't pay off.

happyjack27
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Re: SpaceX News

Post by happyjack27 »

Skipjack wrote: Reusing the center booster in a 3 booster configuration would be a challenge. The center booster would be too far down range to fly back to the launch site. It would have to land on a gigantic barge downrange. I think that would not be every cost effective.
would also have to be re-optimized, for higher vacuum, lower thrust. so now you've got a different vehicle.
Personally, I would rather go the opposite way and make a reusable SSTO based on the tanker stage alone (without the booster). According to Musk a stock tanker could be an SSTO without a payload and might have trouble coming back (though he might not have thought that part through all the way).
by the numbers, a stock tanker - presuming it has sufficient thrust (which would make it poorly optimized for second stage) can just barely make it to leo - with no payload, and that means no fuel to deliver.

two stage gives more delta-v / can deliver more mass. the first stage needs a lot more thrust so has a poorer mass ratio. discarding this when you dont need it anymore can more than pay for the mass cost of the extra engines you have to lug up. giving you an overall improvement in delta-v.

if anything, though, perhaps they can make the tanker (and ship) longer -- give it more fuel.

this would mean fewer refueling launches, and ability to deliver more mass per launch.

so... still 2-stage, but make the top stage longer. also means it's engines would start earlier, lower vaccum and probably more thrust needed.

D Tibbets
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Re: SpaceX News

Post by D Tibbets »

Not mentioned for a few posts, so it bears repeating. The tanker is the IPT spaceship with the crew and cargo spaces replaced with additional tanks. As such the engines and flight controls are virtually the same. There is minimal additional cost for designing this variant. More payload delivered to LEO means new design, more mass of the spaceship itself, modifications to heat shield perhaps, different landing characteristics, etc. etc. The high reusability of the booster and tanker and to a lesser extent the IPT means the cost of design and development eats a larger portion of the per flight costs when considering 3 (or even 4) spacecraft or boosters as opposed to two and a half. There are tradeoffs. The only scenario where higher capacity clearly wins is with low reusability. And even then it is because the system costs are higher, perhaps much higher.

If you want to build a third ship, I wonder if going smaller is better. An "scout IPT" with a capacity for 10-20 passengers instead of 100 , at least for the first few iterations of the transport may be substantially easier and cheaper. This could still begin a development and colonization plan, especially if a group of ships are sent at each opportunity, as Musk envisions. As for numbers a colony is only well established once children are born. Transporting and supporting only adults is not a colony in my eyes, it is an outpost or station.

Dan Tibbets
To error is human... and I'm very human.

Skipjack
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Re: SpaceX News

Post by Skipjack »

happyjack27 wrote:
Skipjack wrote: two stage gives more delta-v / can deliver more mass. the first stage needs a lot more thrust so has a poorer mass ratio. discarding this when you dont need it anymore can more than pay for the mass cost of the extra engines you have to lug up. giving you an overall improvement in delta-v.
So? Once you have a highly reusable LV that can deliever most payloads to LEO for very little money, everything changes. If I can do more than 8 flights to LEO with the payload of a F9 for the cost of a single FH, increasing the payload per flight becomes less important and flightrate becomes more important. The ITS will fly only every two years (which is why its reuse is limited to 12, not as much for technical reasons). This increases maintenance cost per flight. The actual maintenance cost of the ITS would be much lower if it was flying more often.
Personally, I don't care much about Mars. It is "nice" but I have serious doubts about colonization with eve 90 trip times and average trip times will be higher in the beginning. Talk to me again, when the average trip times are 30 days. But an SSTO RLV with the capacity of an F9 and <2.5 million cost per flight opens up possibilities. Suddenly every nation can afford sending people and equipment to space and sending 5 or so people to the moon would cost some 10 million USD, or so. Factor in improved economics over time (look at how F9 has improved!) and I can see another reduction by a factor of 3 or more.
The only reason why Musk needs to do 2 stages is because he wants to send 100 people to Mars in one launch. For the purpose of a mass exodus within a really short time, and this purpose alone the ITS architecture with two stages and as few flights as possible makes economic sense. I just dont see that many people going at current technological level. Too risky and too little reward.

happyjack27
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Re: SpaceX News

Post by happyjack27 »

Skipjack wrote: The only reason why Musk needs to do 2 stages is because he wants to send 100 people to Mars in one launch.
No, musk needs two stages because at first you need a lot of thrust-to-mass-ratio so you need a lot of engines, and then for the rest of your trip you barely need any thrust-to-mass-ratio so you barely need any engines.

You can get a lot more deltav if you don't take the mass of those unneeded engines with you.

This relationship does not depend on how many people you send - be it 1 or 100,000.

happyjack27
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Re: SpaceX News

Post by happyjack27 »

http://arstechnica.com/the-multiverse/2 ... rs-vision/
"..Since you’re doing aerobraking to slow down, that means you have to land, so if instead you had landers, then you could land a much smaller mass—you could land the people in groups of landers.”

Then, it’s just a matter of taking the same reusability SpaceX is already presuming they’ll have with the spacecraft and applying it to the landers. “You’ve got a hundred people in your spaceship that’s now in orbit, and you use, like, five or six landers—they all land, the people get off, then they Sabatier up some new methane, they lift off, grab some more people, and so on. So they ferry people back and forth from the ship, and then while they’re busy colonizing Mars, these things just ferry more and more created fuel up to the ship until until it’s full and they return to Earth or whatever,” Weir explained. “This seems like a much nicer thing than taking this gigantic ship, landing it on Mars, and then having to lift it off of Mars again.”
at the extreme end of this, there's extreme skydiving - just give everyone a spacesuit and a parachute. give the cargo a huge parachute. the parachute would be made out of thin-film solar. so then you'd re-use that at the bottom. or it's inflatable transparent that you reuse for an inflatable greenhouse or habitat. any case you reuse it.

then instead of refueling with landers, you'd have a tanker or two on the planet that would refuel it. and a transport to bring all your return people back to it at once.

however,
1) if you have a transport on the ground, why not just send that all the way back?
2) a landed transport makes for a great temporary habitat and fuel depot. not to mention storage. oh, and you can use the rocket engines to grill. space tail-gating.

---

another way you could go with this is to have one big lander. a detacheable third stage, that can thrust back up and rendezvous with the craft left in orbit. like they did on the moon missions. this reduces both the mass you have to land and the mass you have to launch. basically you're saving a round-trip for the difference in mass.

you'd still have to refuel it though - maybe have a tanker on mars.

now that you're not landing the thing, you could go a step further: take off the heat shields, remove some engines... optimize it for space-only flight. then on the earth side you'd need a landable transport to rendezvous. so what you'd have now is a shuttle.

shuttle would only need about 3 deltav each way, and minimal thrust.
earth tanker and transport would be pretty much the same as now
mars tanker would need a little over 4 deltav, more thrust, heat shield. might as well make it the same as the earth one

mars transport - now here's the cool thing - you know how the transport has 6 vacuum engines on the outside, 3 vectorable engines on the inside? well let's say the transport is the part with the 3 vectorable engines and just "plugs in" to the back.

now you don't need the other 6 engines because you really don't need the launch-level thrust-to-mass. so the "shuttle" is essentially just a big fuel tank that you haul back and forth.

now when it gets to the earth side, there's an earth transport waiting there for it, full of passengers and cargo. and either you just swap passengers and cargo (presuming you sent some from mars), or the earth transport also has a detachable core, and you just detach them both and swap.


EARTH <-- tanker,transport with swappable core --> LEO <-- shuttle (just a big fuel tank) with swappable core --> LMO <-- tanker,core --> MARS


alternatively, the shuttle could have its own high isp engines, though that'd be more complex because because now you're "core" would have to be split into a small engine cluster and heat shield, and a detachable payload.

EARTH <-- tanker,transport with core,core payload --> LEO <-- shuttle (just a big fuel tank+high isp engines) with swappable core payload --> LMO <-- tanker,core,core payload --> MARS

at this point you might not really need the mars tanker - just use the core, and have fuel as the core payload. (only reason you need them on the earth side is 'cause you need a lot more delatv to reach orbit) likewise you if you can transfer payload directly between the transport and shuttle, you wouldn't need the core on the earth side.


EARTH <-- tanker,transport with payload --> LEO <-- shuttle (just a big fuel tank+high isp engines) with swappable payload --> LMO <-- core with payload --> MARS

so now you have the "packet" analogy. - your "packet" is the payload, your network is the shuttle, and the decoder/encoder are the earth<->leo and mars<->lmo launch and reentry vehicles.

however, for the cost of this shuttle, you've added complexity and more vehicles. (booster,tanker,transport,payload,shuttle,core (6 vehicles) vs booster, tanker/transport (2 vehicles)) i think elon musk said they ruled out a shuttle system, at least for starting out.
Last edited by happyjack27 on Sun Oct 02, 2016 6:20 pm, edited 2 times in total.

Tom Ligon
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Re: SpaceX News

Post by Tom Ligon »

I know you guys don't trust newspapers, but I just saw this on page A10 of the Saturday, Oct 1 Washington Post:

Implication of sabotage adds intrigue to SpaceX inquiry
After rocket explosion, company wanted a look at competitor’s roof
BY CHRISTIAN DAVENPORT christian.davenport@washpost.com
ECONOMY & BUSINESS

This is about SpaceX wanting to know more about the mysterious bang before the explosion. This mentions that they are interested in an "odd shadow", then a white spot on the roof of a nearby building (about a mile from pad 40) that belongs to ULA. SpaceX was not allowed to inspect the roof, but the Air Force did and found nothing suspicious. So, time to review video again.

happyjack27
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Re: SpaceX News

Post by happyjack27 »

Tom Ligon wrote:..but I just saw this on page A10...
since when were web pages labelled [letter][number]? (j/k)

hanelyp
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Re: SpaceX News

Post by hanelyp »

happyjack27 wrote:http://arstechnica.com/the-multiverse/2 ... rs-vision/
"..Since you’re doing aerobraking to slow down, that means you have to land, ..."
Uh ... no. Aerocapture (aerobraking into orbit) is finicky about burning off enough delta-V but not too much, which is harder to get right than aerobraking straight to landing. But with some lifting body maneuvering to control how deep into the atmosphere you go and how much drag you get it can be done.
The daylight is uncomfortably bright for eyes so long in the dark.

happyjack27
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Re: SpaceX News

Post by happyjack27 »

hanelyp wrote:
happyjack27 wrote:http://arstechnica.com/the-multiverse/2 ... rs-vision/
"..Since you’re doing aerobraking to slow down, that means you have to land, ..."
Uh ... no. Aerocapture (aerobraking into orbit) is finicky about burning off enough delta-V but not too much, which is harder to get right than aerobraking straight to landing. But with some lifting body maneuvering to control how deep into the atmosphere you go and how much drag you get it can be done.
We have the technology to do this. It's just crunching numbers. Computers have come a long way since Apollo one.

In fact... *searches iphone app store for "realtime aerocapturing maneuver adjustment for spacecraft navigation and guidance"*

Tom Ligon
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Re: SpaceX News

Post by Tom Ligon »

SpaceX must be interested in a building roof on Harrison Island. Go to Google Maps and use their Earth View.

Launch Complex 40 is at coordinates 28.561975, -80.577208.

I have previously determined that the camera that produced the internet footage was at roughly 28.525465, -80.641189, just east of the KSC visitor's center, SW of SLC 40. My thinking now is that the camera must have been elevated, possibly on the roof of the building at 28.524184, -80.641143. Otherwise I would expect the large building on Harrison Island might obstruct the view. The amount of camera shake when the main blast wave is heard suggests a roof position.

Along the line between these is a large building at 28.552022, -80.590100. This looks like it is about the right distance from the pad to be the one described. The 3D view of it shows a tall door, so it may be a vehicle assembly building. A nearly square area NE of this seems to be a power substation, not a building. So maybe this is what they're interested in. It is close enough for a good sniper shot.

I see a roof at the bottom left of the image, in the foreground, but have not spotted activity on it. The structures above that are engulfed by flame or smoke and showered with debris, so they're probably at SLC 40 itself, and a bad place to shoot from. A long structure between the launch tower and the first lightning tower to the right of the launch tower does not become obscured, but seems too close to be far outside the blast. There's a white spot that fades in and out of view on its side, possibly venting vapor. It may pop to your attention as you view the video, but I think it is persistently there, and the position would not seem to have a clear view of the rocket.

So I don't know what caught their attention. Maybe they found another video.

Skipjack
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Re: SpaceX News

Post by Skipjack »

happyjack27 wrote:
Skipjack wrote: No, musk needs two stages because at first you need a lot of thrust-to-mass-ratio so you need a lot of engines, and then for the rest of your trip you barely need any thrust-to-mass-ratio so you barely need any engines.
The point was that he wants to send a very large payload (larger than any before) to mars and he only has a perfect launch window every two years (when mars is closest). For operations in earth orbit and even smaller scale missions BEO, an SSTO based on the tanker ITS would be more economic.
The reasons for that are that a smaller SSTO RLV has less maintenance (no staging needed) and can fly more often with a large variety of payloads (e.g. other commercial payloads). There is no standing army of engineers waiting 2 years between flights until mars is back close to earth. The ITS has little use beyond mars colonization. You might be able to launch a couple to serve as large space stations or maybe a lunar base. But that is about the extent of what they are useful for. The same goes for the booster. So I am saying scrap the booster, change the 6 vacuum Raptors on the tanker ITS to a version that is closer to the sealevel one, replace the cargo- fuel tank with a payload shroud. And you have an SSTO RLV with the payload of a falcon 9 1.1 (or more). Enough to mount a full Dragon2 and launch astronauts to ISS for 600k each. Would probably get better/cheaper over time. Same goes for cargo. For GEO and BEO missions, use multiple launches, orbital tugs and dedicated space craft that may be assembled in orbit. Even 20 launches of this SSTO RLV would still be cheaper than a single F9 launch is now. So there is no economic argument against orbital assembly with the exception if want to launch a huge amount of mass at once to a single destination. Anyway, I hope that Musk considers building this SSTO based on the ITS. If not, maybe they would sell a version of the ITS to 3rd parties. At less than 2.4 million a launch, I am sure that there are quite a few that would love this sort of capabilities. The military for sure is one.

kunkmiester
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Re: SpaceX News

Post by kunkmiester »

How big of a torus style space station could you launch for the 350 ton payload plus whatever you get for scrapping this ship and just using it as a giant booster?

If you can just start putting people in space, never mind on Mars, plenty of people will pay plenty less. Then all we need is Gundanium and Minovsky particles. :D
Evil is evil, no matter how small

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