Sunday, May 19, 2013


The 493m Bennu asteroid comes close to Earth's orbit every six years. NASA will be giving Lockheed-Martin $1.04b to retrieve about a few ounces to a few kilograms sample of it. It will be over 150 years before its 0.071% potential of impact threatens the earth.

Is this the right way to spend a billion dollars? When two billion dollars would start a colony on mars? Thus making it even less expensive and safer for the colonists that follow.

Or we could have a rock... er rather, some ground up rock. Space dust. Tons of which the earth is hit with daily. If they found kryptonite maybe, but I suspect nothing more than what's already on the periodic table will be found. They aren't even funding the space mining companies that would follow through.

They are funded though. Including the unspecified cost of NASA's Goddard Space Flight Center running the mission-control systems for the flight.


Arizona CJ said...

A billion seems like one hell of a high price tag for a NEO sample return.

I'm of the opinion that a NEO (and also a cometary) sample return, combined with on site geological research, is very important for both ISRU and planetary defense, but a billion? That seems outrageous.

Why not put out a bid request and see what New Space can do, on a payment on delivery basis? They won't do that though - it'd make them look far too bad.

BTW, regarding Mars... I do see your point on the one-way mission regarding costs. However, I'd like to see a return option *if* it wouldn't be a show-stopper. Would you object to a return capability being added if it was cheap and easy?

The thing is, it can be done cheap and easy if we abandon old precepts. The Sundancer or similar moduals that would be left in high Martian orbit take care of the hard part (They'd need a small reserve delta-v to make the Mars-Earth voyage). Reentry at Earth is an issue, but that could be handled with a minimalist approach; take along a small, light reentry vehicle, such as the reentry capsule of a Soyez (with an improved heat shield). (way too much delta-v would be needed to get the Sundancers into earth orbit to make a transfer viable, so they'd need to take along the reentry gear).

Seems to me that the expensive and complex part is a Mars ascent vehicle. That's what I'm getting at; that doesn't need to be big and heavy. Mars' escape velocity is only about 11,000 mph, compared to over 25,000 for Earth. Low orbit is even easier, around 4700 mph compared to about 17,000 for Earth.

That makes single stage to orbit very easy on Mars. Even easier if you do away with spacecraft. A simple cylinder with a rocket engine on one end and accel couches for astronauts in suits on the other would get the job done. With the performance needed, it doesn't have to be efficient. It can be cheap and simple.

I'm wondering if a simple LOX-methane blowdown engine would suffice. Lower ISP for sure, but it'd be cheap and simple, and you can get the fuel from ISRU. That'd make it very light downmass, as well as cheap.

It wouldn't need to be large; with even an average fuel fraction, something the size of a PAM-D could probably do it. Okay, just looked, and actually, the PAM, which uses the Thiokol Star 63D motor, could do it. Actually, it could more than do it, because the payload would be a lot smaller than the approx 4000 lbs it currently boosts by 5400 mph. It'd be just a few men in space suits plus the lightweight canvas couches. Hrmm, adjust the propellent for a slower burn to avoid high G issues, and a Pam might be almost a ready made Mars ascent vehicle, lacing only a tiny apogee kick capability to put it in orbit (it's a solid).

But, if you went the ISRU route to minimize downmass, use the lander tanks for fuel tanks, and rig them in a simple frame. (no aerodynamics to worry about for this). You could probably uses the frame elements from the lander tanks too, especially if they were made with this ideas in mind. Use the landing couches from the manned landers for couches. So, your only major downmass for an ascent capability would be... the engine, plus whatever was needed for ISRU - and for the latter, you're probably going to be doing ISRU to get O2 anyway.

Just some crazy thoughts from the Arizona lunatic. :)

ken_anthony said...

Great comment CJ. I like crazy. Let me take your ideas as a jump off point and do ya one better.

First we consider the return mission separate from getting there.

The Sundancer is presumed to have hall thrusters for returning to earth but there is still a potential mass problem. If you add crew and supplies would it still have the earth return delta V? That's just a question of how much ion engine fuel you carry so let's assume we brought enough from earth for that (waving hands frantically.)

I'm going to disagree with taking a Soyez and offer an wild alternative. First, the Dragon is about one mt lighter and more capable. Second, we don't have to send it with. We can send it on an earth return around mars and have it meet up with the Sundancer on the return trip (now we're space faring baby!)

For the ascent vehicle I think we should just bite the bullet and build a mars specific SSTO. It shouldn't be that hard. Raptor is too much so it would need at least three smaller methane engines placed like the superdraco are around the Dragon. Compromise on three crew and send it twice to fill a six crew vehicle in orbit. Or two crew sent three times if mass requires it. Ground control should land it empty. It would need to hold enough fuel for a round trip.

Zubrin's ERV prices itself out of the competition.

Anonymous said...

Interesting conversation guys. I would like to point out that the re-entry velocities involved in Mars return are much greater than those involved in space station return, or even lunar return. Soyuz is not capable of dealing with re-entry from anything more than low earth orbit. Dragon, on the other hand, was designed from inception to be capable of Mars re-entry velocities, which is why its heat shield is massively over-engineered for current purposes. It is the clear choice for the mission you are discussing, if we are talking about off the shelf technologies.

Chris in Western Australia