Author Topic: IAC 2017 -- ITS v0.2  (Read 46805 times)

Online AncientU

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Re: IAC 2017 -- ITS v0.2
« Reply #180 on: 09/13/2017 02:32 PM »
...


A Raptor Vac, based on the 1MN test version, with thrust of about 1.4-1.5MN, would have a bell diameter of around 2.6m, so you could fit 6 of them in a 9m diameter easy, perhaps even with an increased expansion ratio of ~250:1, and get a few more seconds of ISP, and therefore reach performance goals with less of a need to use exotic carbon fiber materials (save that for the next, larger version of ITS) It would also be able to fit a ~1.8m diameter Sea level Raptor engine in the middle for landing.
...
The booster will use ~18 of the original sized 3MN sea level Raptors.
...
That's just my guess after ruminating over the numbers. We'll all find out in a few weeks.  8)

My numbers would be four vacuum Raptors, plus a three sea level Raptor middle row for spaceship.

19 Raptors on booster in 1-6-12 hex pattern.
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Offline ZachF

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Re: IAC 2017 -- ITS v0.2
« Reply #181 on: 09/13/2017 02:49 PM »
...


A Raptor Vac, based on the 1MN test version, with thrust of about 1.4-1.5MN, would have a bell diameter of around 2.6m, so you could fit 6 of them in a 9m diameter easy, perhaps even with an increased expansion ratio of ~250:1, and get a few more seconds of ISP, and therefore reach performance goals with less of a need to use exotic carbon fiber materials (save that for the next, larger version of ITS) It would also be able to fit a ~1.8m diameter Sea level Raptor engine in the middle for landing.
...
The booster will use ~18 of the original sized 3MN sea level Raptors.
...
That's just my guess after ruminating over the numbers. We'll all find out in a few weeks.  8)

My numbers would be four vacuum Raptors, plus a three sea level Raptor middle row for spaceship.

19 Raptors on booster in 1-6-12 hex pattern.

Yeah, woops I meant 19 for the booster, not 18.  :P

Four Engines in a ring isn't as efficient as 6 though at using surface area, if the center engine is the right size 5 might be better. The original ITS was a good design at using all the surface area it had.

The 9m ITS will have about half the surface area for ~42% of the size. It would be wise to use this ~20% increase in sectional density to increase thrust in the lower stage, and increase the ER (and therefore ISP) in the upper stage.

EDIT: misunderstood your proposal, perhaps is a better usage of space? It would need 3 versions of Raptor though
« Last Edit: 09/13/2017 02:53 PM by ZachF »

Offline rsdavis9

Re: IAC 2017 -- ITS v0.2
« Reply #182 on: 09/13/2017 03:07 PM »
So booster uses 19 fullscale raptors in 1-6-12
US uses 4 subscale vacuum and 3 subscale sealevel

Is that what you mean?
bob

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Re: IAC 2017 -- ITS v0.2
« Reply #183 on: 09/13/2017 03:16 PM »
So booster uses 19 fullscale raptors in 1-6-12
US uses 4 subscale vacuum and 3 subscale sealevel

Is that what you mean?

Exactly

I'm assuming the first round of 'full scale Raptors' come in a bit smaller than the IAC advertised thrust, so around 630klbf apiece or smaller.  As the engine capability grows, booster will be stretched and flame trench reinforced based on actual performance... maybe getting 10-20% incremental improvements at a minimum.
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Online AncientU

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Re: IAC 2017 -- ITS v0.2
« Reply #184 on: 09/13/2017 03:22 PM »
... It would need 3 versions of Raptor though

Not really. FFSC would mostly need a nozzle change to be a fine vacuum-optimized engine -- maybe a niobium extension on basically a standard bell (don't know if this is feasible, but seems that retracting the  large vacuum nozzles when landing on an unprepared surface would be a good idea).
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Offline ZachF

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Re: IAC 2017 -- ITS v0.2
« Reply #185 on: 09/13/2017 03:25 PM »
here is a diagram of my proposal vs. yours.

Both present nearly identical area for Vac nozzle exits.

I assumed 1x3MN for mine and 3x1MN for yours for landing engines. The thrust for the vac versions is bascially ITSv16 scaled to 42%, divided by the number of engines, and rounded.

Both would probably be capable of increasing the expansion ratio to around 250:1 with the same TWR.

What kind of ISP increase would a 250:1 vs 200:1 Raptor vac get?

Mine would only need 2 versions of raptor vs 3, and would have 3x symmetry.

Either would work well.  ;)
« Last Edit: 09/13/2017 03:27 PM by ZachF »

Offline guckyfan

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Re: IAC 2017 -- ITS v0.2
« Reply #186 on: 09/13/2017 03:38 PM »
Flight qualifying the subscale Raptor would enable them to fly a methane vehicle in 2020. Later they can change the thrust structure and stretch the tanks going for a bigger even more capable vehicle.

So the redesign of the vehicle for 3x raptor is not VERY hard?
How about the factory line for subscale first then full scale?
Is there a use for a subscale that will exist after full scale is available?
Thereby justifying the expense.

Likely about as hard as redesigning F9 from v1.0 to v1.1 and the octaweb.

I think that is about right. My suggestion is under the assumption, that getting a capable methane driven fully reusable vehicle flying is the paramount consideration. For deploying the satellite constellation and for getting to Mars ASAP.

Online AncientU

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Re: IAC 2017 -- ITS v0.2
« Reply #187 on: 09/13/2017 11:41 PM »
Do we have a resolution of a potential date conflict with the Tesla semi truck reveal?

Semi truck reveal:  September 28
IAC presentation:  September 29

Problem solved.

Quote
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Online wannamoonbase

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Re: IAC 2017 -- ITS v0.2
« Reply #188 on: 09/14/2017 01:12 AM »
Do we have a resolution of a potential date conflict with the Tesla semi truck reveal?

Semi truck reveal:  September 28
IAC presentation:  September 29

Problem solved.

Quote
Tesla Semi truck unveil & test ride tentatively scheduled for Oct 26th in Hawthorne. Worth seeing this beast in person. It's unreal.
https://twitter.com/elonmusk/status/908108029777686528

Tesla needs to do a delivery/work van for those that run around a city all day but don't exceed 200 miles.

regarding IAC, the time between now and the 29th is killing me.  I need info on the Raptor!
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Online Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #189 on: 09/14/2017 01:15 AM »
Why? Bigger batteries last much longer, can accept a faster charge rate, and have more power (torque).
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Re: IAC 2017 -- ITS v0.2
« Reply #190 on: 09/14/2017 06:39 AM »
Excuse me people. This is not a Tesla thread. Back to IAC 2017 please. Thank you.

Offline john smith 19

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Re: IAC 2017 -- ITS v0.2
« Reply #191 on: 09/14/2017 07:30 AM »
I think the cheapest path is to go for the final 9m booster and spacecraft from the start.

Using subscale raptors will cost more in the long run.
Assuming that going from subscale to full scale isn't VERY hard.
Go for composites from the start. Maybe metal lined tanks.
Many other things can probably be skimped on and done later.

But the major components will benefit the cost by being done in final form from the start. Having the same engines for both stages is a known benefit. All composite will take longer but avoids a major redesign later.

Its all about how much effort later to change versus how much easier it is now.
Yes, it's the idea of not doing something twice, at different scales, and possibly having problems that show up only because you are making a part at sub scale.

The trade off is to make it with more margin as a "boiler plate" that may not be able to perform the full mission.

Which incidentally was exactly the project plan for SABRESkylon as well.
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Offline ZachF

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Re: IAC 2017 -- ITS v0.2
« Reply #192 on: 09/14/2017 02:07 PM »
Another thing to remember, Elon talked about RaptorVac having a 3m/10ft diameter engine bell that is full regen cooled.

https://twitter.com/elonmusk/status/877341165808361472?lang=en


This matches up perfectly with my scenario of 6x subscale Raptor vacs for second stage propulsion. With a 9m body diameter they work out to ~2.9m, within likely rounding margins.
« Last Edit: 09/14/2017 02:09 PM by ZachF »

Online AncientU

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Re: IAC 2017 -- ITS v0.2
« Reply #193 on: 09/14/2017 03:53 PM »
Another thing to remember, Elon talked about RaptorVac having a 3m/10ft diameter engine bell that is full regen cooled.

https://twitter.com/elonmusk/status/877341165808361472?lang=en


This matches up perfectly with my scenario of 6x subscale Raptor vacs for second stage propulsion. With a 9m body diameter they work out to ~2.9m, within likely rounding margins.

The limiting thrust operation for the spaceship is take-off from Mars, I think.  In-space burns could easily be accomplished by any pair of vacuum-nozzled Raptors -- only need four for redundant pairs.

So, number of sub-scale engines that must be lit on Mars surface to get off the ground is deciding factor... not sure what wet weight plus return payload will be that dictates this value.
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Online oiorionsbelt

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Re: IAC 2017 -- ITS v0.2
« Reply #194 on: 09/14/2017 04:02 PM »
 Elon will likely reveal some more hardware advances at the IAC. Raptor progress seems like a given. Notwithstanding the apparent failure of the carbon fiber tank I think we are likely to see progress in this area as well.
 What other ITSy enabling hardware would people like to see?

Offline rsdavis9

Re: IAC 2017 -- ITS v0.2
« Reply #195 on: 09/14/2017 04:16 PM »
Another thing to remember, Elon talked about RaptorVac having a 3m/10ft diameter engine bell that is full regen cooled.

https://twitter.com/elonmusk/status/877341165808361472?lang=en


This matches up perfectly with my scenario of 6x subscale Raptor vacs for second stage propulsion. With a 9m body diameter they work out to ~2.9m, within likely rounding margins.

The limiting thrust operation for the spaceship is take-off from Mars, I think.  In-space burns could easily be accomplished by any pair of vacuum-nozzled Raptors -- only need four for redundant pairs.

So, number of sub-scale engines that must be lit on Mars surface to get off the ground is deciding factor... not sure what wet weight plus return payload will be that dictates this value.

If the pressure on mars is 1/200 of earth then vac nozzles may work just fine?
Only need sea level for landing on earth (or titan).

EDIT: another coincidence is that the pressure on mars is almost exactly the vapor pressure of LOX at subcooled temps.
66k

CORRECTION: I had to recalculate and got 59K for mars pressure.

« Last Edit: 09/14/2017 04:38 PM by rsdavis9 »
bob

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Re: IAC 2017 -- ITS v0.2
« Reply #196 on: 09/14/2017 04:24 PM »
Elon will likely reveal some more hardware advances at the IAC. Raptor progress seems like a given. Notwithstanding the apparent failure of the carbon fiber tank I think we are likely to see progress in this area as well.
 What other ITSy enabling hardware would people like to see?
There were hints about gaseous fuel thrusters, ~10ton force each.
Id be very happy to hear more about those.
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Re: IAC 2017 -- ITS v0.2
« Reply #197 on: 09/14/2017 05:11 PM »
Elon will likely reveal some more hardware advances at the IAC. Raptor progress seems like a given. Notwithstanding the apparent failure of the carbon fiber tank I think we are likely to see progress in this area as well.
 What other ITSy enabling hardware would people like to see?

Raptor yes please!

Carbon fiber, sure if he must.  I still think the ITSy boost stage to start, can me metal and US be carbon. 

Evolve to carbon later.

Edit: Change the least amount of variables possible at one time.  They know the aluminum lithium alloy and how to weld it.    Learn how to fly and reuse a huge booster, get experience with the Raptor then move up to new materials. 
« Last Edit: 09/14/2017 05:22 PM by wannamoonbase »
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Offline envy887

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Re: IAC 2017 -- ITS v0.2
« Reply #198 on: 09/14/2017 05:50 PM »
Another thing to remember, Elon talked about RaptorVac having a 3m/10ft diameter engine bell that is full regen cooled.

https://twitter.com/elonmusk/status/877341165808361472?lang=en


This matches up perfectly with my scenario of 6x subscale Raptor vacs for second stage propulsion. With a 9m body diameter they work out to ~2.9m, within likely rounding margins.

The limiting thrust operation for the spaceship is take-off from Mars, I think.  In-space burns could easily be accomplished by any pair of vacuum-nozzled Raptors -- only need four for redundant pairs.

So, number of sub-scale engines that must be lit on Mars surface to get off the ground is deciding factor... not sure what wet weight plus return payload will be that dictates this value.

If the pressure on mars is 1/200 of earth then vac nozzles may work just fine?
Only need sea level for landing on earth (or titan).

EDIT: another coincidence is that the pressure on mars is almost exactly the vapor pressure of LOX at subcooled temps.
66k

CORRECTION: I had to recalculate and got 59K for mars pressure.
They were always planning to use the vacuum engines for takeoff at Mars. They might even use them for landing, or at least to scrub some velocity of before touching down on the landing engines.

The big ITS ship would mass up to 800 tonnes when starting the landing burn, and could fire up to 7 engines at full thrust without exceeding 3 g loads.

Offline ZachF

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Re: IAC 2017 -- ITS v0.2
« Reply #199 on: 09/14/2017 05:54 PM »
Another thing to remember, Elon talked about RaptorVac having a 3m/10ft diameter engine bell that is full regen cooled.

https://twitter.com/elonmusk/status/877341165808361472?lang=en


This matches up perfectly with my scenario of 6x subscale Raptor vacs for second stage propulsion. With a 9m body diameter they work out to ~2.9m, within likely rounding margins.

The limiting thrust operation for the spaceship is take-off from Mars, I think.  In-space burns could easily be accomplished by any pair of vacuum-nozzled Raptors -- only need four for redundant pairs.

So, number of sub-scale engines that must be lit on Mars surface to get off the ground is deciding factor... not sure what wet weight plus return payload will be that dictates this value.

Well, the original ITS had ~21,000kN(vac). I just scaled everything down to 42% for the exercise, when done there is also room to increase the nozzle size/ER because of the square-cube law.

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