Talk:SpaceX reusable launch system development program/Archive 1: Difference between revisions

Revision as of 06:56, 13 April 2015

Revision as of 06:57, 16 April 2015

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This earlier-date material <u>might</u> be worth extending the history back a bit earlier than it now is. If others have an opinion, leave it here. Or you are welcome to use this source to add earlier history yourself. Cheers. [[User:N2e|N2e]] ([[User talk:N2e|talk]]) 03:33, 18 April 2014 (UTC)

== Dubious ==

The article says that ''The challenge of creating a reusable rocket is almost impossible due to the small percentage of a rocket's mass that can make it to orbit.'' and ''Typically, a rocket's payload is only about 3% of the mass of the rocket which is also roughly the amount of mass in fuel that is required for the vehicle's re-entry.'' I couldn't find this clearly stated in the sources mentioned, and while it is true for single stage to orbit reusable vehicles, it is not true for multi-stage vehicles like Falcon 9 / Falcon Heavy. [[User:Mmeijeri|Martijn Meijering]] ([[User talk:Mmeijeri|talk]]) 13:33, 31 July 2014 (UTC)

* The language "almost impossible" is not directly quoted from the source, nor does the source contain any information to support the assertion that the feasibility is low. I personally think that sentence is misleading. [[User:Tesla Tree|Tesla Tree]] ([[User talk:Tesla Tree|talk]]) 18:12, 1 August 2014 (UTC)

::I believe the wording "almost impossible" comes not from the cited article, but the talk that Musk gave before the National Press Club (which is referenced in the cited article). Perhaps the video of the National Press Club presentation where he made that statement should be added as a citation. Further, perhaps it should be identified as a direct quote from Musk rather than simply repeated here. <span style="font-size: smaller;" class="autosigned">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/132.3.57.79|132.3.57.79]] ([[User talk:132.3.57.79|talk]]) 19:12, 5 August 2014 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot-->

::I agree that the wording is poor and should be changed (it isn't almost impossible, it's "merely" difficult. Heh. Merely.). However, that bit about the "3% of the mass of the rocket" is quite true. In most 2 stage rockets, like the Falcon 9, it's more like a little less than 2%. Some particularly well designed, highly efficient, low safety margin, 3 stage rockets can hit 4%. It doesn't go much higher than that. Chemical fuel just isn't energetic enough for better numbers.

::The issue is that adding reuseability to a rocket is estimated to reduce payload to orbit by a bit more than 2 percentage points. For most 2 stage rockets that would mean the extra mass would be enough to stop them from obtaining orbit (less than 2% - more than 2% = nothing making it to orbit). Or, as Musk put it, they have a "negative payload to orbit". The 3% given in the article is just an averaging of the industry standard 2-4% figure. It should be replaced by "2 to 4 percent" IMO. SSTO vehicles face similar problems, by the way. The added weight reduces their payload to orbit to negative numbers. &mdash; [[User:Gopher65|Gopher65]]_{<small>[[User_talk:Gopher65|<font color="green">talk</font>]]</small>} 02:04, 2 August 2014 (UTC)

:::Not all of it is true. It's true that payload fractions are only a few percentage points, but that can be overcome by using multiple stages. Whether that is economical is another question, but there is no doubt that it is physically possible. Whether (reusable) single stage to orbit is possible is not certain. Some believe it is, others are skeptical. Two stage to orbit is generally believed to be possible, and three stage to orbit should be no problem. [[User:Mmeijeri|Martijn Meijering]] ([[User talk:Mmeijeri|talk]]) 08:23, 2 August 2014 (UTC)

::::I just came upon this discussion from a couple of months ago. Took a look. I have added another source to that section about the challenge of achieving reusability on orbital launches from Earth. Hope that helps. [[User:N2e|N2e]] ([[User talk:N2e|talk]]) 03:47, 27 September 2014 (UTC)