KSP Community CubeSat

[Robotengineer]

If we did a Phobos lander, would we be the first to land there?

[Nicholander]

All of us.

[Kryten]

If we did a Phobos lander, would we be the first to land there?

Yes. It's far more likely we'd be the fourth to fail to land there.

[Nicholander]

So you're saying that you think that the Phobos Lander mission would fail? Even though we're planing it to be the 5th or 4th mission?

[Kryten]

Lavochkin have done a lot more than 4 or 5 missions, and they couldn't hack it. They weren't trying to use such a constrained form-factor either.

[Nicholander]

I checked Wikipedia, and the only Phobos mission they ever worked on was Phobos-Grunt, and that was due to a launch vehicle failure, and we won't be doing ANYTHING with LVs, we'll be making the CubeSat.

[Kryten]

Then you didn't check wikipedia very well. They made Phobos 1 and 2.

[astropapi1]

Then you didn't check wikipedia very well. They made Phobos 1 and 2.

And Phobos 2 had a comms failure.

[Kryten]

Computer failure. What's you point? A phobos cubesat would have to perform complex tasks with extremely limited mass, space, data, and power budgets. Combine that with the radiation environment and limited budget for testing, and there's no reason to expect it to do any better.

EDIT:

I checked Wikipedia, and the only Phobos mission they ever worked on was Phobos-Grunt, and that was due to a launch vehicle failure, and we won't be doing ANYTHING with LVs, we'll be making the CubeSat.

The launch was entirely successful. The upper stage only failed because it was a modified version without it's own flight computer-the probe's own computer failed and doomed it.

Edited September 13, 2014 by Kryten

[Nicholander]

Okay, but on the Lavochkin Wikipedia page, it doesn't list Phobos 1 and 2 on the list of spacecraft they worked on, but it does mention it int there history. But the Soviet political and power system was completely different then what we have, and technology has advanced since then. Anyway, Phobos-Grunt was freaking sample return, so they had to make it so it not only lands on Phobos, but it then has to get ALL THE WAY BACK TO EARTH!!!!

[Kryten]

There are plenty of constraints that technology won't solve. Just how is this cubesat supposed to communicate, for example? You won't exactly get a large antennae on a cubesat bus.

[ProjectThoth]

In response to some of your questions:

What do you think about having the Lunar Orbiter orbiting over the Lunar poles, which will give us a clear view of the Lunar poles, which as of now the only pictures we have are just stitched together ones from equatorial orbits.

It really depends on what kind of orbit Astrobotic's first mission is in. Lacus Mortis, the target landing zone, sits at a healthy latitude of 45.0 degrees North. Using a bit of extrapolation (and some rough estimates, because I don't know where my protractor is), it looks like their target orbit is going to be about 65 degrees. That's good news and bad news. Good news: We'll be able to photograph most of the poles from that inclination. (or at least, closer than anyone has been before). Bad news: Jebediah Kerman isn't going to last very long. See, there's these things called "mascons" in the Moon - areas where the gravitational pull of the Moon is slightly stronger - and they can perturb the orbits of low-altitude satellites to the point of crashing into the surface. The simple solution is a reboost every once in a while, but we might run out of propellant a lot faster that way. So this is a pretty big challenge to surmount, but I think we can do it.

I want to see more on that "Spinx" spacecraft of yours.

It's basically a revamped Apollo LM descent stage. Here's a whole quarterly report volume on the thing: https://docs.google.com/file/d/0BzQZ3LhGXAoTVEtRakQ4dFdPSzg/edit?pli=1. Table 4 is close to what the manned version of Sphinx will be, and Table 7 is what it will be with cargo - which is what will debut first.

I'm seeing some concern about our Phobos lander project. Namely, in regards to communication - remember that Sphinx, as a Falcon Heavy upper stage, is able to carry about a half a metric tonne of payload to Mars orbit. Eagle eyed observers among you will note that the TMI capacity of FH is about ten metric tonnes, almost exactly the mass of just Sphinx alone. There's enough of a delta-v margin for Sphinx to complete the trans-Mars injection burn and park in a rendezvous orbit for Phobos. (The latter takes 1.41 km/s of delta-v, and we have about 5.4 km/s to work with). In fact, Sphinx alone could conduct the TMI burn and still make it to Phobos, with 1.8 km/s of delta-v to spare! That's a launch aboard a Falcon 9 right there, and not a Falcon Heavy.

What I'm trying to say here is that we absolutely have enough mass for a communications relay to either be bolted to Sphinx, or as a small spacecraft orbiting Phobos. So don't worry about that so much.

Anyway, tonight I'm going to sketch up some plans for a Phobos lander and run it by y'all. Hope you folks like it.

[Rakaydos]

Launching a 10 ton payload just to get a cubesat or similar to phobos is probably out of our price range- it's more the domain of a "Proper" space program. That's why we've been focusing so much on economizing the D/V budget, to squeeze everything into a 3u that can go up on a normal commercial launch as ballast for much less than a proper launch.

One thing we might consider for a 3u's comunicatios consider is having a 3u that folds it's frame out into a 70cm antenna, or even a 130cm antenna

Edited September 13, 2014 by Rakaydos

[Nicholander]

Also, ProjectThoth, I forgot to mention how it lands on Phobos:

The Phobos Lander CubeSat will have no landing legs, but instead will slow down until it's "Hovering" (I say that in quotation marks because it doesn't have it's engines on to keep it hovering, it just slows down until it isn't going down/falling, and then turns off it's engine(s))just above the surface (20-30 Cm), turn off it's engines, and then change it's attitude using RCS to point horizontally, and on the side of it that's pointing towards Phobos (While it's being horizontal) will have a "Bumper". The bumper will cushion it's small fall towards Phobos, just to make sure nothing gets damaged. It may bounce a tiny bit, but it's negligible and it will land safely, and with out the need for heavy landing legs and the system required to deploy them.

[ProjectThoth]

Launching a 10 ton payload just to get a cubesat or similar to phobos is probably out of our price range- it's more the domain of a "Proper" space program.

Well, it'd be through Astrobotic, and not a one-off thing. It'd be out of your price range if you did it just for one mission. Bear in mind that Sphinx is going to be used a lot for various missions aside from just the Phobos launch.

One thing we might consider for a 3u's comunicatios consider is having a 3u that folds it's frame out into a 70cm antenna, or even a 130cm antenna

It's not the size of the antenna that's gonna be the problem; it's the power. CubeSats are tiny, and the amount of electricity you'd need to broadcast all the way back to Earth is way more than they can produce (the inverse square law isn't your friend at all). Also, without a relay, you'd go dark for about four hours at a time. The mass available in a Sphinx launch is enough for one of those, without a doubt.

The Phobos Lander CubeSat will have no landing legs, but instead will slow down until it's "Hovering" (I say that in quotation marks because it doesn't have it's engines on to keep it hovering, it just slows down until it isn't going down/falling, and then turns off it's engine(s))just above the surface (20-30 Cm), turn off it's engines, and then change it's attitude using RCS to point horizontally, and on the side of it that's pointing towards Phobos (While it's being horizontal) will have a "Bumper". The bumper will cushion it's small fall towards Phobos, just to make sure nothing gets damaged. It may bounce a tiny bit, but it's negligible and it will land safely, and with out the need for heavy landing legs and the system required to deploy them.

Clever, but I'd like to propose something else. A tether a winch, and a wardrobe - er, harpoon.

Basically, the lander would fire a harpoon at Phobos (probably a small rocket-powered thing) at an altitude of about 20 meters, and then the CubeSat would winch itself towards the surface. Simple, no crazy maneuvers, no bouncing (which scares me, seeing as you could escape from Phobos with a bicycle) and probably "dumb" (as in simple) enough to work even without radio contact from Earth. Plus, a rocket-powered harpoon is rather Kerbal, don't ya think?

[Rakaydos]

Also, ProjectThoth, I forgot to mention how it lands on Phobos:

The Phobos Lander CubeSat will have no landing legs, but instead will slow down until it's "Hovering" (I say that in quotation marks because it doesn't have it's engines on to keep it hovering, it just slows down until it isn't going down/falling, and then turns off it's engine(s))just above the surface (20-30 Cm), turn off it's engines, and then change it's attitude using RCS to point horizontally, and on the side of it that's pointing towards Phobos (While it's being horizontal) will have a "Bumper". The bumper will cushion it's small fall towards Phobos, just to make sure nothing gets damaged. It may bounce a tiny bit, but it's negligible and it will land safely, and with out the need for heavy landing legs and the system required to deploy them.

That's assuming we have enough TWR to have a dead stop above the surface, not guarenteed if we went for an Ion engine.

Alternate techniques call for landing "aircraft style" at phobos orbital velocity (of a whopping 8m/s tangental to the surface), and sledding to a stop.

[Nicholander]

Well, how much do you think a little "Bumper cushion" costs and is risky? And compare it to the sled and harpoon. The "Bumper cushion" seems for more practical, cheaper, and safer.

[ProjectThoth]

Well, how much do you think a little "Bumper cushion" costs and is risky? And compare it to the sled and harpoon. The "Bumper cushion" seems for more practical, cheaper, and safer.

I'd feel better if we had landing thrusters, at the very least. Like a short burst of RCS to shove ourselves into Phobos. I'm more concerned with the bumper bouncing off into space than anything else.

[Kryten]

A full set of RCS thrusters would likely fill the entire mass budget, not taking into account anything else.

[dharak1]

If you Orbit phobos first and come to a dead stop within it's sphere of influence as far as i know it would be physically impossible for it to somehow gain momentum and bounce out of the SOI.

[Kryten]

The SOI model doesn't work too well at the best of times; around a body with as irregular a shape and subjected to as high tidal forces as Phobos, it's pretty much useless.

[ProjectThoth]

Alright, I'm feeling better about the bumper landing system. Have any of you done any studies in regards to how we'd fit something like this into a CubeSat?

EDIT: Didn't catch Kryten's comment - agreed on that. Feeling less better about the bumper now.

Edited September 14, 2014 by ProjectThoth

[Rakaydos]

It's been awhile, but most of the phobos studies we've worked on have focused on building ~1500 m/s of delta V into a 4.5 KG cubesat. With a LTO launch instead of GTO, we can shave about a third of that off, but that's still talking about an ion engine that may not have the TWR to do a controlled landing- Real life ion engines are REALLY weak.

[ProjectThoth]

It's been awhile, but most of the phobos studies we've worked on have focused on building ~1500 m/s of delta V into a 4.5 KG cubesat. With a LTO launch instead of GTO, we can shave about a third of that off, but that's still talking about an ion engine that may not have the TWR to do a controlled landing- Real life ion engines are REALLY weak.

Why so much delta-v? At this point, you could use Sphinx for the low orbit - Phobos transfer. Stick to chemical for the landing, mostly because it's reliable and doesn't require so much energy (a CubeSat ion thruster has thrust in the micronewtons at the trade-off of a huge electrical draw).

Here's what I suggest, overall: Stick to chemical, make it as "dumb" (as in foolproof) as possible, and have a Mars-Phobos Lagrange 4 or 5 communications relay in your plans. Additionally, remember that you now have ~500 kilos of mass to work with for both the lander and relay sat, so there's now plenty of room for things like rocket harpoons and landing gear.

I also advise, instead of simply talking about it, to start making diagrams and planning this out in as much detail as possible. Quarterly reports and volumes of them are your friend. This thread is about 120 pages long, and things are bound to get lost in the chaos. Assigning people to doing certain jobs (like two or three folks to review the landing system, two or three folks to study landing sites, and so on) is also a really good idea, and helps when it comes to organizing thoughts. This is also important for when the time comes to sell this idea to the rest of the KSP community/the world.

Also, just to give us a deadline, let's assume a launch date of late July, 2022 and an arrival of April 22, 2023. While that might seem like a long time to go, it's only about 2,853 days away and counting according to this clock.

I think we've got it in us to do something that, literally, nobody else has done before. The make-or-break factor is really organization and putting that first wobbly, semi-confident step forward into the unknown.

(Sidenote: Unless we've already got a name, I vote we christen the lander Scott Manley).

[Nicholander]

But remember, the "Sphinx" is the size of the LEM descent stage, and thus has similar weight. So yes, it is possible for the CubeSat to have harpoons and landing gear if we manage to convince a LV provider to get us there in the first place. But anyway, even if we do get "Sphinx" up an running, why do you need landing gear and harpoons? That weight could be taken up by scientific equipment, cameras, communication equipment, etc. So even if you can put fancy risky landing mechanisms, there's really no point when you got, safer, cheaper, and safer options.

And the launch date? Yeah, that seems reasonable, did you use this "Cosmic Train Schedule"?

For the name, we haven't decided it yet, but I really believe that we should name it KerbSat, like KerbSat-1, KerbSat-2, etc.