Physics of small asteroid transport (with 12 examples)

[SoCalEric]

Not sure where this belongs, but of potential interest to those following Planetary Resources / Deep Space Industries / recent $20m NASA seed funding intent. A rare gem of an academic paper being extremely engineering pragmatic/relevant. Nuts and bolts from JPL database.

http://arxiv.org/pdf/1304.5082.pdf

Easily Retrievable Objects among the NEO Population

D. García Yárnoz, J.P. Sánchez, C.R. McInnes
(Submitted on 18 Apr 2013)
Asteroids and comets are of strategic importance for science in an effort to understand the formation, evolution and composition of the Solar System. Near-Earth Objects (NEOs) are of particular interest because of their accessibility from Earth, but also because of their speculated wealth of material resources. The exploitation of these resources has long been discussed as a means to lower the cost of future space endeavours. In this paper, we consider the currently known NEO population and define a family of so-called Easily Retrievable Objects (EROs), objects that can be transported from accessible heliocentric orbits into the Earth's neighbourhood at affordable costs. The asteroid retrieval transfers are sought from the continuum of low energy transfers enabled by the dynamics of invariant manifolds; specifically, the retrieval transfers target planar, vertical Lyapunov and halo orbit families associated with the collinear equilibrium points of the Sun-Earth Circular Restricted Three Body problem. The judicious use of these dynamical features provides the best opportunity to find extremely low energy Earth transfers for asteroid material. A catalogue of asteroid retrieval candidates is then presented. Despite the highly incomplete census of very small asteroids, the ERO catalogue can already be populated with 12 different objects retrievable with less than 500 m/s of {\Delta}v. Moreover, the approach proposed represents a robust search and ranking methodology for future retrieval candidates that can be automatically applied to the growing survey of NEOs.

Scroll to page 25 for stats on here-and-now known top 12 list of tiny minable asteroids, with upcoming required start/end dates of orbit shifting to Lagrange arrival:

Table 2: Capture trajectories and mass estimates for the best trajectory of each type. (2006 RH120 2Hs 2006 RH120 2Hn 2010VQ98 2V 2007 UN12 2P 2011 UD21 1Hs 2011 UD21 1V 2011 UD21 1Hn 2000SG344 1P)
   Asteroid Departure
   Manifold insertion
   Arrival in Li
   J Total Δv [m/s]
   Duration [yr]
   Isp = 300s
   Mass Ř [ton] [m]

Could anyone here propose breakeven business cases (with what potential hardware) for retrieval of these 12? Preseumably these are a mere 5% (?) tip of of the iceberg of NEOs known by, say, 2016?

[a_langwich]

http://arxiv.org/pdf/1304.5082.pdf

Table 2: Capture trajectories and mass estimates for the best trajectory of each type. (2006 RH120 2Hs 2006 RH120 2Hn 2010VQ98 2V 2007 UN12 2P 2011 UD21 1Hs 2011 UD21 1V 2011 UD21 1Hn 2000SG344 1P)
   Asteroid Departure
   Manifold insertion
   Arrival in Li
   J Total Δv [m/s]
   Duration [yr]
   Isp = 300s
   Mass Ř [ton] [m]

Could anyone here propose breakeven business cases (with what potential hardware) for retrieval of these 12? Preseumably these are a mere 5% (?) tip of of the iceberg of NEOs known by, say, 2016?

Hmm, it appears while the paper studied the trajectories involved in capturing these to loose L1 or L2 orbits, the actual possibility of capturing the entire asteroid is slim.  That last column, struck-out-zero or Phi (m), represents the diameter of stuff they think is actually retrievable, assuming average NEO density, 300s Isp rocket on a Cassini-like spacecraft launchable with an Ariane 5 ECA, etc. 

2-5m diameter balls of mass that could be moved, i.e. not the whole asteroid unless it turned out to be on the very small end of estimates.  The big asteroid 2000 SG344, which might range from 4500 tons to 40000 tons, would have to be severely chopped (or dustbusted in the Keck report vernacular).

They mention their study trajectories assume "impulsive burns" so low-thrust options like SEP don't apply, but if they did, the diameter might go up to 10m.  That makes it likely some of the asteroids could be captured whole, though 2000 SG344 still wouldn't fit.

With regard to a business case, I don't see one yet.  We know very little about these bodies.  The diameter is estimated from a range of possible albedos.  Mass is unknown.  Composition is unknown.  Some have even been speculated to be spent upper stages.  If we knew the composition, we haven't yet developed the tools to extract any useful components.  There aren't any customers in space yet for any raw materials, though we can surmise that perhaps in the future NASA might be interested.  (I suspect none of the other space agencies would be, unless the business offering them originated in their country, and had a large employment footprint.)

If you try to bring material back to earth, you'll have to cover the retrieval mission costs (and years of time waiting for arrival), plus the marginal cost of each launch of a spacecraft to go to L1 or L2, retrieve material, re-enter, and be recovered.

And look at the dates:  the earliest arrival in L1/2 would be 2021, and that trajectory assumes the spacecraft reaches the asteroid by 10/2013 to start moving it.  The other dates are in the 2027 to 2043 time frame.  How are you going to make a business case for that?  I don't think you could get investors, I think you'd need faith-based donors.

I think that's why, when you look at the "asteroid mining" companies, most of them are focused on "asteroid identification and characterization" right now.  In the near term, some appear to be focused on "NASA mining" for money, while others are looking for a second, income-generating uses for their asteroid telescopes.

(Sorry for the wall of words.)