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Mjolnir wrote: Using it as a heat source to avoid spending electrical power on heat would be the more effective approach... [...] Might need to remove some insulation to keep from overheating, though, considering the vehicle probably didn't have the power budget to spend kilowatts on heat to begin with.

He could have done both [...]

And that's exactly what happened in the book. Halved the load on the battery by removing the need for heater, but also tapped into the little bit of electricity output, and had to remove a whole lot of insulation to keep the cabin bearable.

hi hi

I'm still not sure what exactly the RTG was doing there in the first place. Why didn't they leave it in space? Also, I'm kind of curious about the rover's motor. The Tesla Roadster has a 215 kilowatt electric motor in it, for comparison.

Presumably it was there to convert the martian atmosphere into rocket fuel for the ascent stage that the rest of his crew escaped on early on in the story.

icekatze wrote:I'm still not sure what exactly the RTG was doing there in the first place.

I wondered that myself. It was odd that they introduced it without explaining what it was for.

Arioch wrote:

icekatze wrote:I'm still not sure what exactly the RTG was doing there in the first place.

I wondered that myself. It was odd that they introduced it without explaining what it was for.

Yeah, the movie doesn't do a good job of explaining it except to say "we moved it far away when we got here".

But in the book, yeah, it was used to generate fuel for the MAV.

RedDwarfIV wrote:

Arioch wrote:

icekatze wrote:I'm still not sure what exactly the RTG was doing there in the first place.

I wondered that myself. It was odd that they introduced it without explaining what it was for.

Yeah, the movie doesn't do a good job of explaining it except to say "we moved it far away when we got here".

But in the book, yeah, it was used to generate fuel for the MAV.

It powers the MAV while it creates fuel.

And now I'm getting the book and movie mixed up. That's what I get for buying and reading the book the day after watching the movie.

Does the rover flip in the movie?

alpha wrote:Does the rover flip in the movie?

No.

Huh. I just noticed, in the book he uses the second rover as a trailer. In the movie, there doesn't seem to be a second rover, the first rover just has a trailer already.

Probably seen elsewhere already, but SpaceX just stuck the landing of a falcon 9 first stage.



And delivered some communication satellites to orbit too a guess, but damn. They did it.

hi hi

Grats to Space X. They've joined a relatively small club, with the good ol' McDonnell Douglas DC-X, and the Blue Origin New Shepard.

icekatze wrote:hi hi

Grats to Space X. They've joined a relatively small club, with the good ol' McDonnell Douglas DC-X, and the Blue Origin New Shepard.

They did that a few years ago with the Grasshopper. They've started a new club with this...that's the first stage (and 9 of the 10 engines) of a rocket that just delivered 11 satellites to orbit. DC-X and New Shepard are dwarfed just by the payload this thing pushed to ~2 km/s at 80 km altitude before turning around and coming back.

Return to flight after a failure, with improvements in engine thrust, densified propellants, deployment of 11 satellites to LEO, an on-orbit restart of the second stage to demonstrate capabilities needed for geosynchronous launches...and first stage flyback and recovery at Landing Complex 1, all completely successful. Quite a Christmas for SpaceX.

Now all they need to do is a couple repeats with the same rocket stage.
Its good to see they accomplished it, but it is after all only the first step.

hi hi

I mean, it's very impressive that they landed the first stage, don't get me wrong. There are very few people who have done a successful vertical landing of a rocket. But plenty of rockets have delivered satellites into LEO, so that's really not a first.

I am, of course, very curious to see if they can put it back into orbit and save money with the recovery, or if maintenance costs will expand beyond initial projections like in recoverable projects of yesteryear. Definitely something to watch.

icekatze wrote:hi hi

I mean, it's very impressive that they landed the first stage, don't get me wrong. There are very few people who have done a successful vertical landing of a rocket. But plenty of rockets have delivered satellites into LEO, so that's really not a first.

I am, of course, very curious to see if they can put it back into orbit and save money with the recovery, or if maintenance costs will expand beyond initial projections like in recoverable projects of yesteryear. Definitely something to watch.

It's the first that the same vehicle has done both.

It's 90% of the overall launch vehicle, and unlike the Shuttle or the various other spaceplane boondoggles, it doesn't go to orbit. There's no exotic heat shielding tiles, it makes a much gentler reentry at just a few km/s. The added mass required for recovery makes a relatively small difference in the payload, and the added complexity amounts to landing legs, some small cold-gas thrusters, and some grid fins. If they want to pursue full reuse, recovering the second stage on its own is a much easier and less costly problem to solve. (Though they don't currently plan this with the Falcon 9, as the resulting payload capacity would be too limited.)

That's a very substantial amount of the overall launch cost that they don't have to pay on a subsequent launch, and they achieved it without anything that can be expected to cost a great deal...in fact, they're able to significantly undercut their competition while operating the Falcon 9 as an expendable launcher. Just recovering the engines means they can sustain a much higher launch rate for the same manufacturing rate...and the first stage has to be basically intact and operational in order to successfully land, so odds are they'll be able to reuse much more than that.

hi hi

Well, when you put it like that, it sounds basic and easy.

icekatze wrote:hi hi

Well, when you put it like that, it sounds basic and easy.

It's SpaceX. They aren't pursuing cost reduction via the use of ultra-complex supertech, that's Reaction Engines (and pretty much every other spaceplane and SSTO project that's ever existed). They like "basic and easy" wherever they can get it.

Scaling up powered landings to the first stage of an orbital launch system (and not even a small one) is far from trivial...the powered reentry with the thruster firing into a hypersonic airstream in particular is something nobody's ever tried before...but the basic technology required has existed for decades. That doesn't make it less of a big deal that someone's now actually doing it...the launch industry's been stuck in a rut, doing little other than maintaining the status quo ever since the Shuttle replaced the Saturn V. SpaceX has already achieved a huge reduction in launch costs, and first stage reuse will significantly improve their ability to do so. They're aiming for an eventual order of magnitude reduction with a future fully-reusable system...that's going to make a big difference.

hi hi

I imagine it is easy to reduce costs when one doesn't need to have a large research and development department for things like designing new rocket motors. Space X is doing some cool things, and I am trying to give them some credit where it is due here, but they have managed to get a lot of cost reductions by getting free research and development from other sources. Like on the development of their rocket motor.

But time will be the ultimate judge of whether or not this works. The space shuttle was supposed to be a reusable cost saving measure. When they planned it out, they figured on the costs of maintenance, of replacing various parts and thought it would be cost effective, but it turned out to be an order of magnitude more costly than they anticipated.

If Space X is able to significantly undercut their competition with a rocket that is comparable to their competition, then I expect they should eventually come to dominate the market, and none of what I say will make much of a difference, but for now out of 130 some launches worldwide this year, they launched fewer than 10.

One thing that amazes me about a lot of SpaceX re-usability detractors(not aimed at anyone in this thread, just a general comment), is that their payload prices are extremely competitive already, and that's with rockets weighed down by equipment and complexity designed for reuse but sold as expendable. If for some reason reuse is a total bust they could strip out the legs, fins, and I imagine some engine gimbals capability, and launch using all their fuel instead of reserving some for boostback and landing, and have an even cheaper launcher with even larger payload.

icekatze wrote:hi hi

I imagine it is easy to reduce costs when one doesn't need to have a large research and development department for things like designing new rocket motors. Space X is doing some cool things, and I am trying to give them some credit where it is due here, but they have managed to get a lot of cost reductions by getting free research and development from other sources. Like on the development of their rocket motor.

And yet, if they can do this, so can anyone else currently designing a launch system. It's not as if NASA, for example, actually needs to redesign the motors every time it designs a new rocket.

icekatze wrote:But time will be the ultimate judge of whether or not this works. The space shuttle was supposed to be a reusable cost saving measure. When they planned it out, they figured on the costs of maintenance, of replacing various parts and thought it would be cost effective, but it turned out to be an order of magnitude more costly than they anticipated.

It would really be preferable to compare it with something that didn't suffer from such decisive feature creep. The original mission profile for the space shuttle could have been accomplished by a horizontal launch & landing system based on an almost entirely conventional airframe, but the addition of polar orbiting for military launches apparently forced a flyback capability equivalent to the circumference of the Earth. The choice is understandable: NASA was afraid that Nixon or one of his successors would cancel the shuttle like they cancelled Apollo. None-the-less, it makes the shuttle an orange compared to most other launch system's apple.

hi hi

I could be wrong about this, but to my knowledge, NASA has not been sharing their rocket motor blueprints with the Russians or the Chinese. There are some very real concerns with launching rockets with a large number of small motors.

I mean, I am really hoping that low cost space launches will become a reality, but there are still a lot of hurdles left to go. NASA tried to get the Shuttle's main engines reusable for 55 flights, and after years and huge amounts of money, they still weren't able to achieve that goal with all parts of the engine.

“The most fundamental breakthrough is a rapidly and fully reusable rocket. It doesn't help if it's partially reusable.”

- Elon Musk