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#200
by
Lars-J
on 16 May, 2021 18:27
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Are you sure it needs 6 raptors when it will have zero payload ?
Not 100% sure, but these prototypes so far are heavier than they want to make the final Starships.
And there is no realistic option to mount 4 or 5 engines. It needs to be 3 or 6. And I don’t think 3 would be sufficient even if tanks are half full.
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#201
by
cdebuhr
on 16 May, 2021 18:36
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Will it have grid fins.
As SS won't have a payload, you'd imagine they could have far fewer Raptors on BN3.
You could also ask if SN20 will *only* have vacuum raptors if its not going to try and land.
there isn't enough space for three vacum raptor in the center of the skirt.
I didn't say they should be in the centre. I'm saying in their proper position, but without the 3 centre gimbaling raptors.
[... sigh ...]
This is what happens when a few not-as-well-informed-as-they-think-they-are local "experts" who don't know what they don't know spout an I'll founded idea as though it were a "fact". There is a persistent myth that just won;t die here that the SL Raptors are there only for use as landing engines. This is a good example of why its so important to separate fact from opinion/speculation, and also why one need to recognize the limits of ones own understanding.
As others have already pointed out, all six engines will be fired to reach orbit. Even with little or no payload, I
suspect that the TWR just isn't there to get from staging to orbit with only vacuum engines. Plus SL engines are needed for control authority, as the VacRaptors aren't planned to gimbal. I guess
maybe you could only fly with two SL Raptors if you were flying no payload and minimum required fuel?? You'd need to stage above enough atmosphere that the canted flight resulting from off-axis thrust didn't result in aerodynamic unpleasantness.
Edit to add: andyr, please don't take my first paragraph as directed specifically at you, as that is not what I intended. For all I know, you picked this idea up here and ran with it - I've probably done similar myself without realizing it. I do try to make sure what I learn here is sound before I repeat it. Learning who the
real experts are here (and there are a lot of them!) goes a long way.
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#202
by
Kazioo
on 16 May, 2021 18:51
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According to Val's source either 16 or 18 Raptors for BN3.
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#203
by
tbellman
on 16 May, 2021 18:57
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Will it have grid fins.
SuperHeavy, absolutely yes; without them, it can't steer on the way down. Starship, absolutely not; it has no need for grid fins.
You could also ask if SN20 will *only* have vacuum raptors if its not going to try and land.
The flight profile they filed with FCC explicitly states it will do "
a powered, targeted landing approximately 100km (~62 miles) off the northwest coast of Kauai in a soft ocean landing". So it will need sea-level Raptor engines. And as others have already said, you need the thrust vectoring on the way up as well.
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#204
by
soyuzu
on 16 May, 2021 19:10
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Are you sure it needs 6 raptors when it will have zero payload ?
Not 100% sure, but these prototypes so far are heavier than they want to make the final Starships.
And there is no realistic option to mount 4 or 5 engines. It needs to be 3 or 6. And I don’t think 3 would be sufficient even if tanks are half full.
These starships also lacks equipments compare with final ones, and IIUC current 4mm 304 stainless body is sufficient to achieve the 120t target dry mass.
User Onespeed has did a simulation and confirmed 19 engine Superheavy + 3 engine Starship is enough with booster RTLS.
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#205
by
AU1.52
on 16 May, 2021 20:44
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LabPabre shows a launch date of NET June 20th. Where did he get this from?
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#206
by
cdebuhr
on 16 May, 2021 20:53
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LabPabre shows a launch date of NET June 20th. Where did he get this from?
From the FCC filing. Edit: I stand corrected. I just checked and its not there. That said, I'm fairly certain this is from an official source, I just cant recall which one. I'll update again if I find it.
Edit 2: Oh there it is ... 3rd reply on this thread:
So... SpaceX has filed for an FCC STA for the first "Starship Orbital test flight", NET June 20th, 2021.
The Starship Orbital test flight will originate from Starbase, TX. The Booster stage will separate approximately 170 seconds into flight. The Booster will then perform a partial return and land in the Gulf of Mexico approximately 20 miles from the shore. The Orbital Starship will continue on flying between the Florida Straits. It will achieve orbit until performing a powered, targeted landing approximately 100km (~62 miles) off the northwest coast of Kauai in a soft ocean landing.
https://fcc.report/ELS/Space-Exploration-Technologies-Corp-SpaceX/0748-EX-ST-2021
The info in the FCC link gives an operational date range of 2021 06 20 to 2021 12 20. I strongly suspect using this as a NET date for the launch is on the extremely early end of the spectrum, but as far as I know its the only official specific date seen yet.
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#207
by
philw1776
on 17 May, 2021 00:00
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According to Val's source either 16 or 18 Raptors for BN3.
Who is Val?
Val's source???
Not that I disagree. See earlier post.
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#208
by
sferrin
on 17 May, 2021 00:10
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This has the feel of just trying to get a grip on SH handing characteristics without endangering their shiny new launch platform and tower, located just next door to the landing pad. Bringing it back within 20 miles and picking a spot to hit on the water will prove out models and characteristics quite well. As for Starship, they're probably concerned about the TPS - if it allows partial damage, controlling the fall back to Earth could well be problematic. Dump her in the ocean for piece of mind, you know she can land if everything else is good after a re-entry.
I like the plan, but do wish they could find a way to try to save some Raptors. But, in the big scheme, these Raptors have already been written off in the name of forward testing...
Hopefully they fish it (and the Hawaii-bound Starship) out of the water if only to prevent somebody else from doing that. (And they would.)
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#209
by
chopsticks
on 17 May, 2021 04:16
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Just want to point out that Chris B. indicated in the most recent article that the orbital launch will be fully expended.
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#210
by
XenIneX
on 17 May, 2021 08:40
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This has the feel of just trying to get a grip on SH handing characteristics without endangering their shiny new launch platform and tower, located just next door to the landing pad. Bringing it back within 20 miles and picking a spot to hit on the water will prove out models and characteristics quite well. As for Starship, they're probably concerned about the TPS - if it allows partial damage, controlling the fall back to Earth could well be problematic. Dump her in the ocean for piece of mind, you know she can land if everything else is good after a re-entry.
I like the plan, but do wish they could find a way to try to save some Raptors. But, in the big scheme, these Raptors have already been written off in the name of forward testing...
Hopefully they fish it (and the Hawaii-bound Starship) out of the water if only to prevent somebody else from doing that. (And they would.)
Maybe for SH, but I'd pass on recovering SS. They'd have to contract a heck of a salvage fleet to land that fish. The real value here is proof-of-concept so that the FAA is will give the nod for re-entry over the continental US.
So long as they get the data they need, far easier to pop the FTS charges and scuttle the lot.
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#211
by
Pete
on 17 May, 2021 09:03
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The lessons of landing F9 have been learned. Super Heavy requires engineering work because it is a different vehicle, but it is basically an overgrown F9. There's a pretty good chance a prototype with legs will successfully land the first time they try it. Whether SpaceX tries this time is more of a schedule and resource issue.
The Starship's mass and engines is also such that a hover is possible. Not desired, of course, but it does greatly expand the landing performance envelope, and reduces the need for absolute-precision-first-time suicide burn landing that F9 needs to use (due to having TWR >> 1 at all times, even under deepest throttle)
Landing Starship *should*, in theory, be a good bit easier than landing F9 boosters.
Same is true for the SH booster, just even more so.
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#212
by
Kazioo
on 17 May, 2021 09:53
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Manager for NextSpaceflight, had correct info in the past.
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#213
by
Yggdrasill
on 17 May, 2021 10:07
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Since the Starship will be expended, I think it's likely they'll only fly with 3 SL Raptors. They can add the 3 vacuum Raptors when they try to land the Starship.
Hopefully they successfully land the Super Heavy, so the test might only expend three Raptors.
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#214
by
Alvian@IDN
on 17 May, 2021 10:46
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Since the Starship will be expended, I think it's likely they'll only fly with 3 SL Raptors. They can add the 3 vacuum Raptors when they try to land the Starship.
Hopefully they successfully land the Super Heavy, so the test might only expend three Raptors.
Not according to NSF article
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#215
by
JaimeZX
on 17 May, 2021 12:00
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Since the Starship will be expended, I think it's likely they'll only fly with 3 SL Raptors. They can add the 3 vacuum Raptors when they try to land the Starship.
Others have suggested the RVacs are necessary for getting to orbit, even without cargo. I'm not sure what you mean about adding them "when they try to land the Starship." RVacs are not for landing... on Earth anyway.
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#216
by
chevvie
on 17 May, 2021 12:02
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Since the Starship will be expended, I think it's likely they'll only fly with 3 SL Raptors. They can add the 3 vacuum Raptors when they try to land the Starship.
Hopefully they successfully land the Super Heavy, so the test might only expend three Raptors.
They are trying to land starship. It'll just be in the ocean, but the landing profile will be the same as it would have been for a landingpad. So they will need those raptors.
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#217
by
BZHSpace
on 17 May, 2021 13:02
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According to this picture taken by Mary maybe BN3 will have more than 18 Raptor SL ?
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#218
by
edzieba
on 17 May, 2021 13:25
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According to this picture taken by Mary maybe BN3 will have more than 18 Raptor SL ?
9 fully visible pairs of non-gimbal-non-throttle Raptor ports (one for fuel & one for oxidiser each) means a ring of at least 18, possibly 19 or 20 depending on lens focal length.
8 angled ports on the thrust puck matches the expected 8 gimbalable-and-throttleable Raptors in the centre cluster.
So somewhere between 26 and 28 raptors still seems to be the target as of that particular dome being completed. No guarantees that dome hasn't since been quietly scrapped for a newer design, though.
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#219
by
BZHSpace
on 17 May, 2021 13:32
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According to this picture taken by Mary maybe BN3 will have more than 18 Raptor SL ?
9 fully visible pairs of non-gimbal-non-throttle Raptor ports (one for fuel & one for oxidiser each) means a ring of at least 18, possibly 19 or 20 depending on lens focal length.
8 angled ports on the thrust puck matches the expected 8 gimbalable-and-throttleable Raptors in the centre cluster.
So somewhere between 26 and 28 raptors still seems to be the target as of that particular dome being completed. No guarantees that dome hasn't since been quietly scrapped for a newer design, though.
I like the configuration :
-SN20
3 RVAC 3 RSL
-BN03
20 non-thottleable RSL - 8 thottleable RSL