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Reuse vs Expend discussion (and other cost related issues)


PB666

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52 minutes ago, magnemoe said:

No, SpaceX is not giving revenue, the BFR development will be very expensive for one.

At least you could try to tell how much is being injected.

 

I always wondered how did they really manufacture for cheap out of such expensive materials.

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12 hours ago, tater said:

I expect that if FH gets used much, the entire point is not the added mass, it's not the use for interplanetary probes, it's to throw stuff to GEO with full booster reuse in a way that doesn't stress the boosters as much as the GTO landings seem to. This is block 5 FH, I mean, where reuse is not something they tacked on to an existing rocket, but something much more thought out WRT that booster.

FH in fully reusable mode isn't that much of an improvement over expendable F9 in terms of lift to GTO. As a customer, I'd rather choose an F9, since it's 50% 30% cheaper.

Edited by sh1pman
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9 hours ago, magnemoe said:

No, SpaceX is not giving revenue, the BFR development will be very expensive for one.
 

I think Tesla has only made money during one quarter [i.e. 3 months] over its entire life.  On the other hand I expect Musk's [Tesla] stock portfolio has wildly inflated (and I'm hoping both he and Tesla managed to diversify.  That price isn't really sustainable).  Once capitalism starts happening, "profits" and "wealth" don't always have any discoverable correlation.

Solar City is structured for high startup costs and long term profits, which might be some kind of way to diversify Telsa stock sales.  It can only be seen as profitable by counting the long term revenue it has basically already locked in (the electricity it is selling for a profit to people with Solar City panels on their homes).

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8 hours ago, sh1pman said:

FH in fully reusable mode isn't that much of an improvement over expendable F9 in terms of lift to GTO. As a customer, I'd rather choose an F9, since it's 50% cheaper.

Hmmm. Good point, though they could I suppose simply state at some point that they won't expend block 5 boosters until EOL, and charge a premium to expend any that are still flyable. They could at that point be offering a service (transport to orbit), and no guarantee of what vehicle it flies on.

 

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On 3/7/2018 at 2:54 AM, sh1pman said:

FH in fully reusable mode isn't that much of an improvement over expendable F9 in terms of lift to GTO. As a customer, I'd rather choose an F9, since it's 50% cheaper.

That's an assumption, since customers are paying 120 to 132 million per F9 launch and reusable version of the FH is 90 million. Of course this is a wish-wash answer, since if the core cost 40 million, and BE is <64 for an reusable, then the price should be 100 million, which means the customers are paying for additional goods or services that are opaque (and so I used the term several times). Some of the services that they are providing will be service vessels to the ISS (Dragon capsule). The are charging more money for expendable, how much more we cannot tell, but it looks like 40 million-ish more.

I think that Musk implied the other day that if they had enough customers to GTO they could change the amount of fuel the second stage carries, offering a higher performance to GTO. They could, if they wanted to, put metholox on board. But another point is that the second stage does not have to circularize to GTO if the PL has its own ion driven PL, it can push to GTO itself. If instead of pushing 18 T to to LEO it pushes 63 T to LEO they could have any number of rocket systems that would get them to GTO. 

- - - -  Devinating the dV required to get to equatorial GTO from a cape Canaveral LEO300(because you were to too cheap to pay for Arianspace, https://en.wikipedia.org/wiki/American_Samoa, https://en.wikipedia.org/wiki/Puerto_Rico, https://en.wikipedia.org/wiki/Guam) - - -

µ = 3.986 x 1014,   P = (sec/d)(d/y -1)/(d/y) = 86163,    f = 1/P, w = 2πf ,    w = 2π/P,       w2r = µ/r2 ,      r = (µ/w2)1/3     42.163 Mm =aGTO
6.371 Mm + 0.3Mm = 6.671 Mm aLEO
δSPE = µ/6671Km - µ/42163Km =  50,297,430 j/kg
δSKE = (µ/6671 km - µ/42163km)/2 = δSPE/2

The theoretical amount of energy required to reach GTO from LEO300km = δSPE/2. But as we know a Hohmann transfer perfectly done requires two impulses of dV, and because we were too cheap to buy a ride from the equator we need to correct the inclination somewhere in orbit (preferably at the point of lowest velocity).  Assumming that we were intellgent enough to burn at the equator LEO, then its easy enough
However it needs to be done in two steps, in the second step is where you want to start  a = (6671 km + 42163km)/2 =  24417 Km,  Vapogee = V42163 Km  = SQRT(µ * (2/r - 1/a)) = 1607.135 m/s (<--- note: this is the point of lowest velocity), the amount of δV we need to correct the orbit is. δV =  [SQRT(µ/42163 Km)  = 3074] - 1607.135 = 1467.4 m/s.

Next, inclination change. (1607 + 3074)/2 = 2340.5 since we launched from cape canaveral at 28.6 degrees north, we need to change inclination by 28.6 degrees. We could use the nifty equation from my other thread, but in a circular orbit the maximum extent (you launch bearing 90' = due east) is on the unit of 1 is actually the angle your orbit crosses the equator because the orbital plane crosses the center of the earth at also the same angle. So basically 2340.5 * sin 28.6 = 1120.37 meters per second (on the tangent or orthogonal). The total δV = SQRT(1055.62 + 1467.42] = 1846.2 m/s  35.73° ±N. Note that would could have burnt in two legs at apogee  this would have been 769.38 + 1467.4 = 2,236.7 m/s so better to burn on the diagonals than to burn on the orthogonals.

IOW you would have saved 350 dV by launching from the equator, but paid 5 times as much for the ride.

Vperigee, a=24417 KM = V6671 Km  = SQRT(µ * (2/r - 1/a)) = 10,157 m/s our initial velocity was from LEO along the transfer elliptical. This means we needed to add 10,157.644 - 7729.3 = 2428.3

Therefore our total dV from LEO300 to GTO having launched from Canaveral was 4274.3. We can lower this cost even more, during the equatorial transfer burn we could have burnt at an ever so slight angle, lessening the dV required for inclination/circularization at apogee. This is because the 1 - cos (some small angle) is a number close to 1. For example cos 10° = 98.4%, loss = 1.6% but Sin is 17.3%, the closer one is to Θ = 0 the higher the gain of Y per loss in X.

- - -  Devinating the best way to get to GTO to LEO - - - - - - - - - - - - - - - - -

ION thrusters.

So all GTO satellites have solar panels, thus we assume they have power, but also ION drives are cheap, and the typical ION drive has an ISP between 1500 and 3500. http://busek.com/technologies__ion.htm

These little thrusters weigh grams to kilograms So the question is how much fuel do you need per kilogram of satellite weight to get to GTO.

δV = ISP * 9.81 * ln(mi/mf)
for 1500 ISP:  0.2883 = ln(mi/mf) , 1.33 = mi /mf > 25% of the weight of the spacecraft + 10% storage penalty = 27.5% of the satellite is fuel. If you had a 63 ton payload to LEO this means 17.3t is fuel, 45.7 t is yours to keep in GTO.

So basically that basically blows any other launch system out of GTO except SLS launching to LEO and doing the same but getting 90t to GTO. (but the problem is that there is not enough panels you can put around increasingly large space craft to do this to indefinite size, so its possible, but not practical, is better to launch in pieces).

for 3300 ISP: 1.141 = mi /mf = 12.36%/87.64%  Again for a FH LEO of 63 thats 55.2 t to GTO. The problem of solar panels is severe, but not to bad if you are launching 4 satellites to GTO, better request better payload fairings.
Note that the higher the ISP of your ION thruster, the more losses from diffuse impulse. But on the other hand you can use the ION thrusters indefinitely for station keeping, no need for RCS or other thrust systems, and the ION drives only need a tiny stainless steel tubing (like HPLC grade), to feed propellant to 6 motors each weighing less than a kg each. With a 55t space craft the small amount of weight added for 6-12 thrusters is not going to keep you awake at night.

The good of ION is that if you are patient, you can lift maximal amounts to GTO, but drag is the enemy, such that if your launch provider can give you a decent push toward GTO so that you can circularize out of LEO, then this is a good choice, another choice is a variable voltage variable power ION thruster, which pushes low ISP in LEO and high ISP in GTO range. Compared to other engines, this is off the shelf stuff, order today and get . . . well at least before the other guys.

Cryogenic hydrolox.

We have deep space engines that range in ISP from 425 to 462 ISP, these are terrible expensive, and there appears to be a delay, but these will get payloads to GTO and they typically weigh a couple of hundred kilograms.

 If you need your payload to GTO tomorrow, these are your deep space engines (except it will take two + years for your RL10b-2 to be delivered, you are a shrewed planner (who just had a heart attack when you recieved the 30dCOC bill for the thruster).

for 462 ISP: 2.56 = mi /mf = 61.0%/38.94% The cost is that you need >4% storage (61.0% * 0.04%) = 2.44% and the cost of one engine, like the ION drive you are probably making multiple kicks at LEO to boost a.
With fuel and tank and engine factored out, the RL10b-2 can get 22.73t to GTO. 

IMHO, unless you can find a cheap Russian or Chinese substitute, you are better off going with an expendable which can deliver the same payload for 130 to 150 million. An alternative that would be clever is simply use the cheap whatever cryolox engine to push the 2400 dV required to push 3/4ths the way GTO and use the ION drive engines to do a sloppy circulization.   This gets the PL into the 40t range and save alot of time. The weakness of ION drive engines is in attempt to burn at LEO perigee, they own the skys at apogee, so that if you place at high enough apogee where they get full sunlight, they can circularize via spiral mechanics and in a decent amount of time reach GTO. Again since you are dealing with space X you might want to consider methane over hydrogen.

Metholox

for 375 ISP: 3.91 = mi /mf = 68.8%/31.2% The cost is that you need >4% storage (61.0% * 0.04%) = 2.75% and the cost of one Raptor engine, like the ION drive you are probably making multiple kicks at LEO to boost a.
WIth fuel and tank and engine? factored out, the raptor can get 16.92t to GTO.
 

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1 hour ago, PB666 said:

- - -  Devinating the best way to get to GTO to LEO - - - - - - - - - - - - - - - - -

ION thrusters.

So all GTO satellites have solar panels, thus we assume they have power, but also ION drives are cheap, and the typical ION drive has an ISP between 1500 and 3500. http://busek.com/technologies__ion.htm

These little thrusters weigh grams to kilograms So the question is how much fuel do you need per kilogram of satellite weight to get to GTO.

One catch is that between LEO and GTO lie the Van Allen belts.  These are not kind to spacecraft, especially to solar panels.  The other catch is that ion drives are slow, and time is money.

That said, fix this issue (and as you can see, billions of dollars are spent lobbing these things all the way to GTO: funding shouldn't be a problem) and suddenly travel beyond LEO is a solved problem.  Just send fuel and cargo via ions, wait (quite a long time in some cases), and then leave LEO, dock with fuel tanker, hit escape velocity to Mars (or wherever), fire a two month ion capture burn (likely then combined with aerobraking and maybe retrorockets), dock with your trusty cargo ship, land ...

There isn't much data on this problem.  I was convinced that ion craft to the Moon and Mars were the answer, until somebody on this forum pointed out the problem.  The only paper I could find was from the Apollo era, but NASA simply sends ion missions into escape velocity by booster and then turns on the ions (note that NASA thinks they are in the "big rocket" business and politics may have been involved).  I thought there was a British ion mission to the Moon (which would presumably give some data to the issue), but either I missed it or it was cut.

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9 minutes ago, wumpus said:

One catch is that between LEO and GTO lie the Van Allen belts.  These are not kind to spacecraft, especially to solar panels.  The other catch is that ion drives are slow, and time is money.

That said, fix this issue (and as you can see, billions of dollars are spent lobbing these things all the way to GTO: funding shouldn't be a problem) and suddenly travel beyond LEO is a solved problem.  Just send fuel and cargo via ions, wait (quite a long time in some cases), and then leave LEO, dock with fuel tanker, hit escape velocity to Mars (or wherever), fire a two month ion capture burn (likely then combined with aerobraking and maybe retrorockets), dock with your trusty cargo ship, land ...

There isn't much data on this problem.  I was convinced that ion craft to the Moon and Mars were the answer, until somebody on this forum pointed out the problem.  The only paper I could find was from the Apollo era, but NASA simply sends ion missions into escape velocity by booster and then turns on the ions (note that NASA thinks they are in the "big rocket" business and politics may have been involved).  I thought there was a British ion mission to the Moon (which would presumably give some data to the issue), but either I missed it or it was cut.

ION driven spacecraft with fully deployed solar panels are moving though the Van Allen belts at liberty, currently. The only known take down of solar panels in recent history that I know of are the loss of 2 panels on Hayabusa on its way to intercept its target by a freak intercept of a solar ion storm. Van allen belts are particularly harmful to humans, not so much to modern satellites, since the overwhelming majority of satellites use solar panels.

 . . . . .

28sFO.jpg

Compare with: http://www.nasa.gov/images/content/668517main_vab-orig.jpg

ION drives are the way to go, 20 years ago few space craft have ION drives, now many have ION drives. No pesky and dangerous RCS to deal with.

 

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Except that Hayabusa didn't stick around using its ion engines to escape the Van Allen belts, but simply blasted through them on its delta rocket.  It seems rather odd that they would use expensive hydrolox fuel (instead of adding more instruments) to blast out quickly if the on board ion engines could do the job just as well?  All the ion-powered spacecraft I've heard of have been chemically placed in either escape trajectories or at least GTO.  There's a big difference between spending a few hours in the Van Allen belts and spending several months.

Deep Space 1: "At 13:01 UT the third stage burn put DS1 into its solar orbit trajectory" https://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1998-061A
Hayabusa: "As  with  the  NEAR  Shoemaker  mission, it  was  decided  that  the  launch  vehicle  would  provide  an  initial heliocentric orbit. This is achievable via a multi-staged Delta class rocket" https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140004799.pdf  OSIRIS-REx: "Its hyperbolic escape speed from Earth was about 5.41 km/s (3.36 mi/s)" (from the infallible wiki)
DAWN: "reaching escape velocity with the help of a spin-stabilized solid-fueled third stage" (wiki, again)

The one exception I could find was SMART-1.  As mentioned above, it was left in GTO.  However, unlike GSO, that is elliptical and *does* imply going through at least some of the Van Allen belts.  In this case it appeared to avoid the inner belts (thanks to launch position) and only had to deal with the outer belt (it started in an extremely elliptical orbit).  It *did* spend about a year working its perigee out of the outer belt.  It is possible that an "inter-belt" area might be a staging ground for moving fuel/cargo beyond Earth (as most of the Van Allen issues happen when crossing the inner belts).  Note that NASA doesn't seem involved at all in this one (ESA mission, Ariane rocket) and had no way to enforce its "rockets must be big" turf mantra.

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1 hour ago, wumpus said:

Except that Hayabusa didn't stick around using its ion engines to escape the Van Allen belts, but simply blasted through them on its delta rocket.  It seems rather odd that they would use expensive hydrolox fuel (instead of adding more instruments) to blast out quickly if the on board ion engines could do the job just as well?  All the ion-powered spacecraft I've heard of have been chemically placed in either escape trajectories or at least GTO.  There's a big difference between spending a few hours in the Van Allen belts and spending several months.

Deep Space 1: "At 13:01 UT the third stage burn put DS1 into its solar orbit trajectory" https://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1998-061A
Hayabusa: "As  with  the  NEAR  Shoemaker  mission, it  was  decided  that  the  launch  vehicle  would  provide  an  initial heliocentric orbit. This is achievable via a multi-staged Delta class rocket" https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140004799.pdf  OSIRIS-REx: "Its hyperbolic escape speed from Earth was about 5.41 km/s (3.36 mi/s)" (from the infallible wiki)
DAWN: "reaching escape velocity with the help of a spin-stabilized solid-fueled third stage" (wiki, again)

The one exception I could find was SMART-1.  As mentioned above, it was left in GTO.  However, unlike GSO, that is elliptical and *does* imply going through at least some of the Van Allen belts.  In this case it appeared to avoid the inner belts (thanks to launch position) and only had to deal with the outer belt (it started in an extremely elliptical orbit).  It *did* spend about a year working its perigee out of the outer belt.  It is possible that an "inter-belt" area might be a staging ground for moving fuel/cargo beyond Earth (as most of the Van Allen issues happen when crossing the inner belts).  Note that NASA doesn't seem involved at all in this one (ESA mission, Ariane rocket) and had no way to enforce its "rockets must be big" turf mantra.

You quoted the reason yourself, so why did you post this. Even if one uses ION kicks, there is generally never enough thrust in the last burn past the periapsis to take advantage of the speed within a gravity well (oberth-like effect) We have been over this sooooo many times in this forum. 'Even if you have ION drive, you might want to carry a small chemical rocket to add speed as one passes the planet one last time'.

And your not paying attention, satellites going to GTO now-a-days are using ION drives, this has been a trend since an ION drive rescued a chemical propelled rocket about a decade ago allowing it to complete its mission.

ION is the way to go, and manf who can't figure out a way to get the solar-electric prop system past VE belts should probably seek a different occupation.

NOTE: in image above, many satelittes with solar panels are operating in the Van Allen belts. The rings indicate belts where satellties are stationed.

 

Edited by PB666
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