7 ms·
Given that you could probably build a Merlin out of solid gold and it would come in cheaper than an RS-25, that's not exactly saying much...
by lutorm 5y ago
Given that you could probably build a Merlin out of solid gold and it would come in cheaper than an RS-25, that's not exactly saying much...
- piercebot 5y agoMaybe not once you consider the R&D costs of figuring out how not to melt a solid gold Merlin engine ;)
- lutorm 5y agoThere is that... ;-)
- jjoonathan 5y agoThis man (err, bot?) contracts!
- Tuna-Fish 5y ago... surprisingly, this is not much of an issue. The key property for keeping a rocket engine from melting is not high melting point, but high thermal conductivity. Because of this, all the parts that touch the hot flame are made from a copper alloy, with a melting point not far from that of pure gold. In the chamber, the hot gases are >3500K, and touching the inner walls with a melting point at ~1400K, yet the walls don't melt, because they are cooled with more power than they are heated.
- jhgb 5y ago> they are cooled with more power than they are heated I'd argue that they're being cooled with equal power, otherwise they could freeze infinitely which is physically impossible.
- Ajedi32 5y agoWow, no kidding. The gold Merlin would be a quarter of the price![1][2][3] (At least in terms of materials.) [1]: https://arstechnica.com/science/2020/05/nasa-will-pay-a-staggering-146-million-for-each-sls-rocket-engine/ https://arstechnica.com/science/2020/05/nasa-will-pay-a-stag... [2]: https://www.google.com/search?q=merlin+engine+dry+mass https://www.google.com/search?q=merlin+engine+dry+mass [3]: https://www.wolframalpha.com/input/?i=%28630+kg+of+gold+in+USD%29+%2F+%24146+million https://www.wolframalpha.com/input/?i=%28630+kg+of+gold+in+U...
- mlindner 5y agoKeep in mind gold is a lot denser, so it'd be a miniature engine if you made it out of pure gold. If you take the volumetric space of all the materials that might lead to a different answer, but that's hard to do. (I guess you could make it out of gold foam.)
- Ajedi32 5y agoProbably closer to half the price of the RS-25 then, assuming normal Merlins are made mostly out of steel: https://www.wolframalpha.com/input/?i=%28%28%28630+kg+*+%28density+of+gold+%2F+density+of+steel%29%29+*+price+of+gold%29+%2F+%24146+million https://www.wolframalpha.com/input/?i=%28%28%28630+kg+*+%28d...
- Diederich 5y agoI LOLd but then had to do the math. Turns out that the dry weight of a SpaceX Merlin engine, in gold, costs almost exactly the same as a production RS-25. Current spot price of gold is $1800/oz. Merlin dry weight is 1380 pounds. 1380 pounds of gold is right at 40 million dollars. Per https://en.wikipedia.org/wiki/RS-25#Space_Shuttle_program https://en.wikipedia.org/wiki/RS-25#Space_Shuttle_program : "A total of 46 reusable RS-25 engines, each costing around US$40 million, were flown during the Space Shuttle program" Beautiful.
- jhgb 5y agoThey cost much more than $40M these days.
- mlindner 5y agoThose numbers are out of date now, they recently restarted production and it turns out each engine is about $150M now for the new production run for the SLS. (Which about the cost of a full expendable Falcon Heavy rocket launch along with all 27 of its Merlin engines.)
- mr_toad 5y agoThat’s what happens when you decide on a product and then ask how much it costs.