|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Stacking Starship and Superheavy
In article ,
says... On 2020-04-05 10:53, Jeff Findley wrote: Again, I have no idea. But do note the last failure was due to the load of propellant in the upper tank. Almost all of a launch vehicle's mass is propellant, so we're talking about *a lot* of mass. Would "normal practice" call for the rocket to be at least able to stand on pad, fully stacked but empty tanks, or it is acceptable to require tanks to be pressurized to support an empty unfueled rocket without cargo? The exception is tanks required to be pressurized for handling, i.e. original Atlas. Originally Starship was to have used transpiration cooling, which meant it would have to hulls (the tank wall and then an outer wall) separated by stringers. That would have stiffened the structure. Cite: https://www.popularmechanics.com/spa...663/elon-musk- spacex-bfr-stainless-steel/ But since Starship has gone to thermal protection tiles, that's no doubt changed. Certainly when they're building and stacking Starship it's not pressurized. That's obvious from the live video feeds of its construction. Now whether or not you can stack a Starship, loaded with a payload, on top of a Super Booster without pressurizing any of the tanks, I don't know. With regards to SN3, I know it was almost confirmed lack of pressure on lower tank did it. Yes, with the upper tank containing so much liquid nitrogen (which is what they use for cryogenic testing), the lower tank buckled. Has there been confirmation this was due to a valve failure vs testing specs that called for what is now known to be inadequate pressure? Starship SN3 failure due to bad commanding. SN4 already under construction, written by Thomas Burghardt, April 5, 2020 https://www.nasaspaceflight.com/2020...ip-sn3-ground- flight-testing/ From above: Elon Musk has since clarified the issue was the result of incorrect commanding resulting in the loss of pressure, as opposed to any material issue with the Starship build. I know Musk has hopes of cutting mucho weight from Starship. Airbus also did for its A380, but in the end, it needed to be much heavier than originally hoped for in order to maintain structural integrity. Initial Starship user's guide says payload to LEO is 100+t. Cite: https://www.spacex.com/sites/spacex/...s_guide_v1.pdf With refueling, the idea is that you can place that payload pretty much anywhere you want including the surface of the moon or Mars. My concern here is that SpeceX may be caught with pressurization limits to avoid catastrophic bursts, and having to add structural strength which would increase weight instead of reducing it. That's pure speculation on your part. Both the Spruce Goose and now the A380 proved to be able to fly, but in the end, the economics didn't make the planes viable. (with COVID19, the A380 is being retiured earlier than planned by many airlines). Time will tell what Starship's ultimate payload capability will be, but 100+t is freaking huge. That's at least 5t more than SLS block 1. SLS block 2 plans on 130t to LEO. But the problem with SLS is that its upper stage can't be refueled in LEO, so it's payload drops off precipitously to the moon at only 45t. That's the power of in orbit refueling. I have been told here that there hyave been heavy steel rockets in the past. Is there no l=knowledge left of how they were built, how they were welded and how much strength thei had with/without pressurized tanks? I am getting the impression that SpaceX is really strating from scratch here, toying with various promitive build techniques. You're welcome to your impression since SpaceX's iterative design process still seems to elude you. Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
#2
|
|||
|
|||
Stacking Starship and Superheavy
On Tuesday, April 14, 2020 at 4:59:54 AM UTC-4, JF Mezei wrote:
On 2020-04-12 15:41, Jeff Findley wrote: changed. Certainly when they're building and stacking Starship it's not pressurized. That's obvious from the live video feeds of its construction. If am I not mistaken,the current stacking of cylinders has never progressed to a point where the the cone was put on top. Full height stacking was only acheived for the PR model used for the press conference, and that was a structure of beaten up panels welded together. Considering the size/weight of the cone that is already built, it seems to be a hefty weight added to those fragiles cylinders below. Starship SN3 failure due to bad commanding. Thanks. Strange though that someone would send a command to open a critical valve during the test when all else would be stable. If this happened at the end of the test, releasing pressure from wrong valve, would Musk have tweeted that the test was succesful and it failed with an error in de-tanking? Side question: Also, I heard the lower tank was filled with water with some pressure added after. (and there was no frost on it). Musk mentioned that steel is stronger at cryo temperatures. Is the strength gained at cryo tempoeratures just icing on cake or is it a significant amount? Also, another side question: Considering water is not compressible, would filling a tank to the brim and closing valve give tank rigidity? Or does the cylinder really require outward pressure greater than what water can provide to maintain its shape? Initial Starship user's guide says payload to LEO is 100+t. Cite: Wouldn't this be an aspirational tareget at this point since they haven't yet built anything that goes to Orbit? With refueling, the idea is that you can place that payload pretty much anywhere you want including the surface of the moon or Mars. But commercially, can launching Starship and then waiting for another rocket to come and refule it be competitive with current crop of disposable rockets? That's pure speculation on your part. Speculation is all that can happen until SpaceX actually builds and flies a Starship with whatever thermal shielding installed. Time will tell what Starship's ultimate payload capability will be, but 100+t is freaking huge. That's at least 5t more than SLS block 1. SLS block 2 plans on 130t to LEO. SLS has no viable commercial uses. (would it even be allowed as a NASA rocket?). You're welcome to your impression since SpaceX's iterative design process still seems to elude you. Question stands. If seel rockets have existed before, shouldn't ApaceX' iterative design have started at a more advanced stage to improve from existing older steel rockets? I get the impression SpaceX is really starting from stratch as if steel rockets had never been built/welded togtether before. I will only comment on one of your comments: Actually water is compressible but that's irrelevant to the discussion. Water will indeed impart rigidity to a container. Just look at any disposable water bottle as an example. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
starship? but ........ROTFL ! :-) | [email protected] | Policy | 11 | March 6th 20 01:24 PM |
Starship fuel costs | Alain Fournier[_3_] | Policy | 3 | February 2nd 20 03:35 PM |
Starship usefulness ? | Jeff Findley[_6_] | Policy | 2 | September 22nd 19 05:57 PM |
100 Year Starship | HVAC[_2_] | Misc | 10 | November 2nd 10 02:04 PM |
French Starship | Chris | SETI | 3 | August 9th 05 06:45 AM |