SpaceX is testing new powerful engines for its mission to Mars | Hacker News Reader

SpaceX is testing new powerful engines for its mission to Mars

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114 pointskungfudoi29 comments

For those who aren't already aware, tomorrow (Tuesday 9/27) at 1:30pm CDT (18:30 UTC) SpaceX will be revealing their Mars colonization plans in full at the International Astronautical Congress.

The live stream will be available here: https://youtu.be/A1YxNYiyALg

Venus' atmosphere is a better colonization target than Mars from every conceivable angle. I don't think they have really thought this through.

My understanding is that Venus' surface conditions aren't great, and that one needs to be miles above the surface for tolerable conditions.

That being said since you seem to have thought about this I'd be curious to read any resources you can recommend.

The grandparent is talking about Venus atmosphere.

It seems the conditions in the upper atmosphere of Venus are acceptable. If you can manage living in floating cities (that it's cool but makes it a very difficult endeavour) then, Venus is close to Earth than Mars and the gravity is similar to the one in Earth.

As always, Wikipedia have this covered: https://en.wikipedia.org/wiki/Colonization_of_Venus#Aerostat...

PS: I'm upvoting the GP, by the way. Why people downvote instead of asking for clarification.

The GP was mostly downvoted because of the unnecessarily supercilious tone. Instead of explaining why they thought Venus was better for this purpose, GP just chose to end with a haughty-sounding "I don't think they have thought this through." Considering GP is a random stranger on the internet, and "they" is SpaceX/Elon, the downvoting is natural.

Maybe. But I think that it's, precisely, because we are random strangers in the Internet and we all know how easy is to misunderstand intentions by text, that we should think two times before downvoting.

It's my personal opinion that downvoting is used too easily in HN.

Sometimes it seems that we are trying to filter opinions that we don't agree with, instead of policing good manners and filter irrelevant to the subject comments.

It turns out that that the atmospheric mix of Earth's surface (of N₂ and O₂) would naturally settle at the atmospheric column very near where the temperature is pleasant by Earth standards. Such floating colonies would basically be completely palatable by Earth standsrds (albeit perhaps with temperatures more reminiscent of Australian outback or Qatar than those of Europe or the US).

Floating colonies present their own issues, but it would solve concerns about long-term low-gravity impacts of Mars or the challenges of requiring a fully-pressurized environment suit all the time outdoors.

I love the idea colonizing our sister planet Venus. Nearly identical in size and composition to Earth - but so volatile. Mining resources would there would be practically impossible due to the pressure on the surface, never mind the cataclysmic surface turn-over events. On top of that, due to the lack of a magnetosphere, solar winds often react directly with Venus' upper atmosphere...

On Mars we might be able to build large stables domes, or close off caverns for additional radiation shielding. We could mine the planet itself for resources, and even grow crops there.

You do realize that, if for any reason, your colony loses flotation and drops toward the ground, everybody dies a horrible death.

The idea is that you would use breathable air as the lifting gas to prevent this problem. The pressure difference would be low enough that it would take an event that would be fatal to everyone anyways to cause a rapid drop.

In my understanding the biggest issue is getting the mass of the structure there as you can't easily mine the surface and it doesn't have any moons to get a bulk of the material from, so you would have to wait for asteroids of the right type to be in position to mine on your way there.

At that altitude, the atmosphere doesn't shield you from radiation, you are closer to the Sun, so there is more of it, the planetary magnetic field just isn't there to compensate, the surface is inaccessible so you can't use it and, if anything fails, you fall to a fiery, corrosive death in minutes.

Not that it's not worth terraforming, eventually, but Venus is marginally better than a space station. Pretty much the only thing it offers is gravity.

This combined with the recent congressional bill $20B budget for NASA's manned Mars mission (yes, you read that right) is very good news for the next generation of space.

The bill, introduced by Ted Cruz and Marco Rubio, among others, has good bipartisan support. https://www.commerce.senate.gov/public/_cache/files/f9467082...

I don't have time to look through this since my PDF reader isn't allowing me to search it, but how much of it is allocated to a manned Mars mission that does not use SLS? I have very low expectations for SLS, and I'd much rather see them support SpaceX's efforts. It does call explicitly for the continued use of SLS.

http://www.usatoday.com/story/news/politics/2016/09/21/senat...

I do agree strongly with the general sentiment that NASA's goals should not be changed every time we get a new administration, but SLS seems like such a pork barrel project.

Note as the GP mentioned that this bill comes from the likes of Ted Cruz (Texas) and Marco Rubio (Florida). What government agency do those two states have in common?

The space program isn't really about exploring space, it's a jobs program.

LiftOff[1] hosts had an interesting hypothesis on Elon Musk's mission to Mars business strategy. If SpaceX can land on Mars early enough to convince Congress that they can do it quicker and cheaper than NASA, they can eat NASA's lunch by taking over manned missions to Mars. That would be a huge payoff for SpaceX.

[1] LiftOff episode 26: https://www.relay.fm/liftoff/26

That looks like it covers all NASA operations, and $20B is the usual number.

From wikipedia:

>> As of August 2016, a scaled version of the[12][verification needed] Raptor engine has been shipped to Texas where it will undergo development testing.

I was looking at the pics and thinking this thing is way too small for what it is meant to be. But after reading wikipedia I understand. The pics/tests are of a tabletop version. The real engine hasn't been built yet. So it's good news, but not the news I was looking for.

Title should perhaps reflect the fact that the "new powerful engine" doesn't yet exist for testing.

From /r/SpaceX, the estimates is that this is a Raptor engine at similar size as the Merlin engine they currently use in Falcon 9.

If so, it'd be about 1/3 size of the "real" Raptor. Though, they also have a contract to develop a Raptor-powered F9 upper stage, so this size could be potentially for that.

His latest tweets are a bit hard to interpret but they say target thrust is 3x Merlin, and 3x chamber pressure, meaning they look similar size if they have a similar area ratio.

I think the combustion chamber and throat are going to be of roughly similar size, but Raptor is going to have a bigger nozzle, because if you expand to ambient (or slightly below), the higher pressure engine naturally has a larger area ratio.

Anyway, in general, the nozzle in a high pressure engine can be a little smaller for the same thrust, but that effect is not 3x.

Maybe they haven't yet fabricated the big nozzles so they first test it in a very underexpanded condition.

> His latest tweets are a bit hard to interpret but they say target thrust is 3x Merlin, and 3x chamber pressure, meaning they look similar size if they have a similar area ratio.

Does it mean three Merlin engines can be replaced with one Raptor engine?

The pics / tests are absolutely not a tabletop version.

Here's Musk's pic from the test:

https://twitter.com/elonmusk/status/780275236922994688

You can see a staircase to the bottom-right, and the railing on the left side (if built to code) is likely 38" tall. It looks like the nozzle is roughly a meter across.

Edit: This one shows the scale a bit better:

https://twitter.com/elonmusk/status/780278836860628992

Further edit:

Everyone is rightly pointing out that it's not a huge engine, but two things to keep in mind.. Musk's ISP figures correspond to operating in a vacuum and of course at that point the bell will be significantly larger (14ft like mentioned). If used for the first stage, the Raptors will likely have similar-sized bells to the current Merlin engines. The bell is just the expansion chamber and doesn't really relate to the actual engine size (except of course to optimize expansion ratio).

The shuttle engines weren't huge, but the bells were quite large, I think the expectation is that the Raptor will be between 1/2 and 1/4 of the Shuttle engine size/weight:

http://extras.mnginteractive.com/live/media/site200/2012/092...

That's still rather small. For scale here is some of the shuttle's engines for comparison. http://guard-lee.com/img/SpaceShuttleAtlantis.ssme.JPG

Ed: This test is probably ~1/3 scale.

Those are still tiny. Unless Musk has invented some new radically new classical physics, that bell is nowhere near big enough to match the shuttle engines, not at the published isps. Maybe I'm wrong and he deserves a noble prize. Or maybe his tweets aren't the full story and this is a scaled technology demonstrator.

Perhaps someone should rewrite the raptor's wikipedia page to indicate that raptor is in a different league. Pics from this "test firing" are right beside numbers claiming thrusts above shuttle, which is comical given the size differences between the engines.

https://en.wikipedia.org/wiki/Raptor_(rocket_engine)

>>Raptor - 2.7 MN (610,000 lbf) Shuttle main engines - 512,300 lbf (2,279 kN)

This is thought to be the Raptor prototype SpaceX is developing under a USAF contract for a methalox Falcon 9 upper stage concept.[0] Thus it's about the size of a Merlin 1D-Vac. Nobody is claiming otherwise.

[0] http://www.defense.gov/News/Contracts/Contract-View/Article/...

full scale production version will be ~14 feet in diameter: https://twitter.com/elonmusk/status/780296017254023170 (for reference, f1 in saturn v were 12.3ft. (!))

A naive question: with all those benefits of methane/LOX engines why weren't they widely used previously instead of kerosene/LOX engines?

Methane can be generated on Mars using the Sabatier reaction to refuel for the trip home. Methane should help re-usability as there will be less soot on the engines. Methane can self-pressurize and SpaceX has lost two rockets in 14 months due to suspected problems related to their helium pressurisation system.

What does it mean by "Methane can self-pressurize"?

I wish I knew for sure. It is just something I read. Rockets need to maintain the pressure in the tanks as fuel is depleted. Most fuels will not vaporize fast enough as they are used. Helium seems to be the best option but hard to obtain on Mars. I guess nitrogen is another choice but it is less than 2% of a very thin Mars atmosphere. I am not sure if methane will do the job by itself or if you might need to heat some up.

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