Reusable SpaceX Rocket Has Implications For a Return To the Moon (examiner.com)

MarkWhittington writes: While it is unclear what, if any, implications the recent successful landing of the first stage of the Falcon 9 first stage means for the future of space travel, planetary scientist and space commentator Paul Spudis suggested that the feat and the similar one performed earlier by Blue Origin could have some benefit for a return to the moon. In the meantime, a test of the engines in the recovered first stage had mixed results. The engines fired alright, but SpaceX CEO Elon Musk reported, "thrust fluctuations" that might have been caused by "debris ingestion."

Comments

Duh!

[taiwanjohn]

Would dropping the cost of getting payloads to orbit have implications for a return to the moon? Hmm.... let's see... I can't quite tell...

Re:Duh!

[ustolemyname]

I originally had this knee jerk response as well, but after I RTFA (I know, bad form) I understand he's actually talking about how these technologies translate into vehicles that never operate in earth atmosphere. Specifically that all extraterrestrial rockets before now have been single use, and more advanced multi use rockets aid long term manned missions outside of earth orbit (If one can consider the moon such).

Re:Duh!

[Rei]

Unfortunately, LOX/RP-1 like SpaceX uses now isn't a great fuel for lunar operations. For a small lunar craft, you want something that has very small, light and simple engines, like a monoprop or hypergolic biprop; if your landing craft is bigger, you want something very high ISP. In both cases it's about keeping your mass down because you're so far down the chain on the rocket equation that any small change in mass (esp on the return stage) has a huge impact on the launch mass. Things that LOX/RP-1 excels at, such as thrust, aren't very important in lunar operations. And it would be extremely hard to make RP-1 there because of the shortage of carbon (even hydrogen is unavailable in most locations, but there are some isolated places where it appears to be present in good quantities).

In terms of lunar-manufactured propellants, obviously LOX/LH has gotten a lot of attention. But another interesting one is ALICE - aluminum-ice. Aluminum is an extremely energetic metal - we don't see this side of it often because its surface coating of aluminum oxide is so effective at shielding it. But aluminum can burn not only in oxygen but also carbon dioxide and water (which is why when you weld aluminum you can't use CO2 as a shielding gas). There's only a few other elements out there whose oxides aluminum won't gladly strip the oxygens from at high temperatures - which is why thermite works, and why it can explode fiercely in contact with water. Its affinity for oxygen is so much greater than water's that the two actually make a pretty strong propellant combination - the key is getting past that oxide layer (which has been achieved pretty well in lab scale propellant mixes). The main advantage of ALICE over LOX/LH in lunar operations is not having to deal with leaky, frigid, low density hydrogen.

Unfortunately, while aluminum oxides are incredibly abundant on the moon, ALICE doesn't work where you don't have water ice. You can't just burn a stoichometric ratio of aluminum and oxygen because the hydrogen is actually very important - burned aluminum (aluminum oxide) condenses out at very high temperatures. No gas = no expansion = no thrust**. You need another gas - the lighter the better, and nothing beats hot hydrogen - to take the heat from the aluminum oxide (not just the heat of combustion, but also the heat of condensation). So this rules out most of the moon, only water-rich areas (albeit, those are the places you'd want to set up a colony). Elsewhere, you could use excess oxygen as your heat transfer gas, but at 16 AMU, it's no lightweight. Another possibility would be to outgas helium from regolith, but you'd have to go through a lot of regolith for that much helium.

On Mars it's much easier, as both carbon and hydrogen are abundant. SpaceX rightfully realized that for Mars you either need a very high ISP or a local propellant supply in order to have reasonable launch masses, and have opted for the latter with the Raptor LOX/Methane engine that they're working on. But that's just one of numerous possibilities on the red planet. A more unusual possibility involves the use of the abundant soil perchlorates as an oxidizer with any number of potential fuel species - they're easier to store than LOX and lower energy to produce (albeit lower performance).

** Likewise, when aluminum is added to a hydrocarbon mixture, the optimum ratio of oxygen, hydrocarbon and aluminum is one where the carbon only burns to CO, not CO2 - you want your carbon exhausts in a gaseous form, but your main goal as far as energy release goes is to burn the aluminum; the extra energy you get from carrying additional oxygen to fully burn the carbon is more efficiently spent carrying more stoichiometric mix of aluminum and oxygen for them to burn together.

Re:Duh!

[taiwanjohn]

I also RTFA (admittedly, after I posted) but I still think it's pretty obvious to anyone who pays much attention to space development issues (like, you know, readers of Air & Space). For that matter, this isn't really that much of a step change in terms of lunar landers. The author talks about "Developing a reusable cryogenic space vehicle," but the F9 is only half cryogenic, it's kerosene fuel is chilled to very low temps, but it's not the same as LH2 or liquid methane.

We could build a reusable lunar lander here on earth and put it on the moon pretty easily, but it's not much use if we don't also have some ISRU infrastructure to produce fuel up there too. That gets damn expensive at $60M~$200M per launch, but begins to look more feasible at $5M~$10M. That cost savings is the key enabling factor, not the novelty of design.

The 'big deal' about SpaceX's feat is that they soft-landed a booster stage on earth, enabling reusability for the first time in history. We've been soft-landing stuff on the moon for decades.

why land on legs?

[140Mandak262Jamuna]

The goal of landing the rocket on three legs seems to be a very great challenge. Especially on a floating platform that is bobbing in the sea. They are able to get the speed and targeting precise enough to pull it off once, and got very close three times now. May be they should be thinking of a recovery system that is less demanding than this.

These rockets are putting some 50000 lb in LEO. It hurts to add weight that reduces pay load. But SpaceX claims the first stage is worth 60 million dollars. May be if they would come up with some kind of system that would fire a cable with grappling hooks at the last moment to snag a cable hung between towers like a clothesline and end up hanging without hitting the ground. It could be heavier than three struts and take some away from payload capacity. By that might be less demanding than precisely landing on three legs, and save enough money make up for it in the next launch.

But anyway it is an amazing achievement. I really hated to see Wired mag calling it "botched" in its head line. May be it is not an inaccurate description, may be they were using standard headline language to find smaller words. But still, if most projects achieve this much in their botched operations ...

Re:why land on legs?

[Rei]

The rocket launches upright. It's designed to bear loads vertically being imparted through its base. It's not designed to dangle from a cable from its nose. Plus, in terms of "things that can go wrong", grappling onto elevated cables sounds far worse than landing on legs.

From the look of it, the real culprit this time was ice, from all of the fog. That's the leading theory as to why the leg didn't latch. Unfortunately, icing on aerial vehicles in general has killed an awful lot of them over the course of modern history.

Re:why land on legs?

[waTeim]

In this case it is now suggested that the cause was simply leg #3 -- there are 4 legs by the way -- failed to lock out due to the failure of a locking collet possibly because of ice buildup, but like you said still impressive. Using legs seem to be easier than arresting the fall with cables; the cables would weigh a lot as they would need to withstand decelerating 25 tons; they would have to uncoil explosively with an aiming system, a launcher and enough energy to throw out the cables; and even though this falcon 9 did come close to being exactly on target (1.4 meters) -- pretty good after being 100 km in space -- that's still off-center enough to cause problems with such a cable system. Finally, this was the last of the Falcon 9 v1.1, the next version, which already flew in December in fact, have improved landing gear.

Re:why land on legs?

[Rei]

So we're totally going to colonize the universe, but look out for the ice fog!

You mean the stuff that regularly takes down airplanes, despite over a century of experience?

Re:No new ideas then?

[GrumpySteen]

The article was written by someone who has no connection to NASA and it does not say that NASA has made plans to return to the moon. Here's a list of NASA's future missions. "Moon" is not on the list.

So still no chance of reading the article before opening your mouth then AC?

Re:Lessons from SpaceX landing

[Rei]

Huh? Were you thinking of stowing away in the Falcon's first stage?

There are no plans by SpaceX to ever have people land in that manner. Dragon (the part humans actually ride in) has both parachutes both retrorockets, only one of which needs to work, and a degree of "crumple zone" (shock-absorbing legs plus the heat shield and service hardware) in case of partial failures of either of the two.

Perhaps you also missed the fifty or so times that the SpaceX newscasters added the word "experimental" before the word "landing". Would you prefer that like most companies they keep their development work in secret? Or should every company be like them, with, say, car manufacturers releasing footage every time, say, a new experimental safety-critical system ends up with a test car plowing into a fence?

Re:Go back to the Moon why?

[Punko]

I do not agree with your statement's overall claim.

However, in order to make you feel better, you can think of these space ventures simply as income redistribution. The "rich guys with a fantasy for space" and "wealthy people" you refer too spend money doing this. Lots of money. This money goes to high-tech jobs that pay well, that in themselves allow money to be distributed. If more of the 1% spent their money this way, there would be even more money distributed around, driving the economy that you and I derive our incomes from.

So rather than being negative on this, you should be banging the drum to make more and more of the 1% interested in this. Make those 1%ers prefer to spend their resources acquiring expensive services that feed the highest paying technical staff, We don't want those folks spending their money on things or on low-value services, we want them to spend them on services that can only be provided at great cost by technical people. Get those bank accounts spending money on high tech services provided by your neighbours !

Re:Lessons from SpaceX landing

[Grench]

The first stage isn't supposed to land with humans on board. It's just designed to land so that they don't have to build another one from scratch every time they launch a customers' payload into orbit.

This will mean they don't have so much cost per launch, so they can either pass those savings on to their customer (customer wins), don't pass those savings on to their customer (SpaceX profits), or pass SOME savings on to the customer (so both parties benefit).