Notes from Josh Hopkins’ LM “Plymouth Rock” Presentation (8 Dec 2010)

A couple of weeks back, I got an invitation from Josh Hopkins (a friend of mine from Lockheed Martin’s Advanced Programs group) to attend a colloquium he was going to be presenting at up at SwRI’s Boulder office. It turns out the colloquium ended up right in the middle of SpaceX’s COTS 1 mission, so I ended up heading down there after the launch.

Anyhow, Josh was presenting the “Plymouth Rock” mission concept LM has been pitching as a way to do relatively “affordable” missions to Near Earth Asteroids. You’ve probably seen pictures for this mission concept showing two Orion capsules docked to each other. Admittedly, I had been a bit skeptical about this particular mission approach, but Josh did a pretty good job of making his case.

I didn’t get a copy of his actual presentation, but here’s a more detailed paper he wrote on the topic.

Their approach was to focus on the portion of near earth asteroids (NEAs) that had relative inclination, circular orbits close to earth’s. There are probably dozens of objects that fit this description. He mentioned a couple of key characteristics of these accessible NEAs:

  1. The circular, low-inclination orbits close to earth’s orbit keeps the required delta-V for rendezvous and return down to a reasonably low level.
  2. However, because the relative orbital speed of earth and these NEAs is so similar, visit opportunities for any given target are very infrequent (once every 10-20 years).
  3. A corollary to #2 is that since it is easiest to discover such NEAs when they’re close to earth, typically when you discover an NEA, the best time to do a mission is either right away, or 15-20 years from now.
  4. Most of these NEAs are less than 100m in diameter, with many of them less than 30m in diameter
  5. Most of these have relatively high spin rates
  6. Due to the small diameter and high spin rates, some of these objects have negative effective surface gravity.
  7. That means that these objects are very unlikely to be rubble piles, and many are likely solid monoliths.
  8. However, one research group found that a rubble pile NEA with that spin rate would preferentially shed the larger boulders, but due to the high adhesion of the regolith, the regolith would stay behind.  So there could actually be dust pile NEAs in this group.
  9. Smaller accessible NEAs are much more common than large ones.  According to models discussed at the meeting, we probably know less than 10% of the 30m or smaller accessible NEAs, but most likely we know over half of the >100m ones.
  10. Even then, accessible NEA opportunities are rare enough that NEA missions might be better as targets of opportunity rather than the focus of the system design.

There were other points, but I think those were the highlights.

Josh then spent a bit of time talking about the work they did with the dual-Orion and then the Orion + Orion-derived Hab analysis.  Pretty interesting.  For the mission in question they were talking about only two people.  So, having two vehicles allows you to “go to your room” and be alone in a way that a single vehicle couldn’t.  Josh also pointed out that an Orion-derived vehicle that didn’t have to be used for reentry, and didn’t have to be designed for launch abort modes, or take the conical form factor could easily double the usable internal volume of an Orion at significantly lower weight.  I asked him afterward if he had looked at other vehicles like Bigelow’s Sundancer or Dragon, and his reply actually made a lot of sense–he had, but there just isn’t anywhere near enough public data on either of those systems to really be able to analyze a mission around them.  It might be worth further investigation once Bigelow or SpaceX have released more information.

While the technical details of the space hardware was interesting, the most interesting takeaway from the discussion was Josh’s point that one of the most important investments if we’re seriously going to go after NEAs is in NEA detection and tracking.  If we only know about 10% of the 30m-class targets, that means that investing in better detection has a pretty high probability of giving a better target for any given launch window.  Especially with the fact that NEAs detected from earth tend to be only up for visit again 15 years from now, there’s a lot to be said for putting money into better detection.  It was suggested that a Venus-distance IR telescope, pointing out away from the sun could probably detect about 50% of the 30m or greater NEA population within only 2-3 years of operations.  Between finding more of them, and getting better orbital data so we can more accurately predict their courses at future dates, you can greatly increase your options for targeting missions.  This makes it a lot more likely that you can find a good interesting mission that’s easy to get to.

Anyhow, I could probably say more, but I wanted to get these notes up there before I forgot to.  I’d suggest reading Josh’s paper and giving it some thought.

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Jonathan Goff

Jonathan Goff

President/CEO at Altius Space Machines
Jonathan Goff is a space technologist, inventor, and serial space entrepreneur who created the Selenian Boondocks blog. Jon was a co-founder of Masten Space Systems, and is the founder and CEO of Altius Space Machines, a space robotics startup in Broomfield, CO. His family includes his wife, Tiffany, and five boys: Jarom (deceased), Jonathan, James, Peter, and Andrew. Jon has a BS in Manufacturing Engineering (1999) and an MS in Mechanical Engineering (2007) from Brigham Young University, and served an LDS proselytizing mission in Olongapo, Philippines from 2000-2002.
Jonathan Goff

About Jonathan Goff

Jonathan Goff is a space technologist, inventor, and serial space entrepreneur who created the Selenian Boondocks blog. Jon was a co-founder of Masten Space Systems, and is the founder and CEO of Altius Space Machines, a space robotics startup in Broomfield, CO. His family includes his wife, Tiffany, and five boys: Jarom (deceased), Jonathan, James, Peter, and Andrew. Jon has a BS in Manufacturing Engineering (1999) and an MS in Mechanical Engineering (2007) from Brigham Young University, and served an LDS proselytizing mission in Olongapo, Philippines from 2000-2002.
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23 Responses to Notes from Josh Hopkins’ LM “Plymouth Rock” Presentation (8 Dec 2010)

  1. Nels Anderson says:

    The IR survey telescope could be parked at Venusian L2, where Venus would block most of the solar disk. Plus, Venus’s gravity well could be used to reduce the delta-V for the mission relative to the delta-V needed to place the telescope into an independent circular orbit at the same distance from the sun.

  2. red says:

    The “Exploration Precursor Robotic Missions (xPRM)
    Point of Departure Plans” slides from the Explore NOW workshop included a possible NEO Telescopic Survey mission:

    “– NEO Telescopic Survey
    • Helio-centric orbit inside the orbit of earth.
    • Would likely focus on identification and remote characterization (size, spin, albedo, thermal inertia, roughness, trajectory determination, etc) to provide robust slate options for HSF exploration.”

    “NEO Telescopic Survey (NTS) Mission Option
    • Current slate of HSF NEO candidates may not be sufficiently robust.
    • Per NASA Johnson Space Center analysis: 44-known NEOs are reachable [by?] humans assuming notional Ares V-class launch vehicle performance;
    – All but 17 may be deemed “too small” to visit by humans
    – Of those, 15 have opportunities in the (very) wide timeframe of interest
    – Of those, only 3 have mission durations on the order of 180 days
    – Of those, only 1 has a launch window in 2025 (the next being 2036 & 2046)
    – There are additional risk factors which could further eliminate candidates (spin rate, binary system, dormant comets)
    • NTS could discover 1000’s of additional objects >100m providing a more robust set of candidate targets.
    • Need to determine if this current slate of candidates is “sufficient” and if size and mission duration limits are valid assumptions.”

    They also had ideas about missions to 1 or small numbers of specific NEOs, and of course Moon and Mars missions as well. The funding for these robotic precursor missions has been mostly or entirely absorbed by things like the SLS, though.

    Hopefully the Orion folks will see that they don’t need the SLS, and put their political weight against it and for the other exploration areas. Carving up SLS funding would allow adequate funding for Orion itself, human-rating Delta IV for Orion, robotic precursor missions to chart a course for Orion, moderate “heavier than current” lift augmentations to rockets we will have anyway, and exploration technology demonstrations, some of which could be hosted on Orion and/or lead to improvements to Orion.

  3. Heinrich Monroe says:

    I don’t believe that parking at Venus L2 is practicable for this purpose. If I recall, at that location the Sun is barely occulted there. At least, that’s the way it is at Sun-Earth L2. Also, keeping something exactly at an L1 or L2 point is propulsion-expensive. Lagrange point deployments actually involve wide orbits around the Lagrange point and the tighter the orbit the more stationkeeping propellant is needed. But the idea of putting such a NEO monitor in the inner solar system is useful. That way, you keep the Sun at your back while you’re looking out. You don’t need any more than sensible telescope baffles to see faint objects if it’s behind you.

    The Plymouth Rock concept is a nice one, but doesn’t address the rationale for sending a human being to a NEO. That rationale strikes me as being kind of thin. As to reconnoitering it for resource development, that particular NEO won’t be available again for a very long time. As to using that NEO to teach us about NEOs for threat mitigation, that’s of some interest, except you never really know how typical the one you happen to be able to visit really is. It may be totally unrepresentative of the one that’s bearing down on us. The Plymouth Rock plan comes across as an excuse to put humans in deep space, which is broadly important to our efforts in space exploration, and very important to Lockheed!

  4. I have consistently heard it said that any human mission to an NEA would be proceeded by a robotic probe. I think the arguments that there aren’t enough NEA targets with the desired parameters is just rigid thinking. That robotic probe need not be a passive observer. It can change the orbit of the NEA to make it desirable for human exploration.

  5. Heinrich Monroe says:

    Absolutely no question that a human mission to such an an object would be preceded by one or more robotic probes.

    Although the idea of changing the orbit of a NEO is a slick one, doing it for an object of any significant size is going to either be hugely difficult or require a very long wait. Not sure what you mean by “passive observer”. Aside from orbit changing, no reason why such a probe could not do telerobotic investigation, which would be very non-passive.

    But still, let’s suppose you can change the orbit of one to make it desirable for human investigation. You send humans to it, and then what? It’s unlikely to be coming back for a long time unless you can get it captured by the Earth-Moon system. And hey, changing the orbit of an asteroid to make it pass close to the Earth may not be seen as a very smart thing to do!

  6. Dave Täht says:

    I am really glad to see not only the NEO exploration idea getting traction but to hear of two proposed missions to make it more feasible.

    Impact/flyby with robotic missions is easier than rendezvous, as you can fly smaller probes with more delta-v. Mission duration is potentially shorter too. It would be nice to have a series of standardized “deep impact” style probes on-hand, to be launched opportunistically.

    You could impact/flyby rocks closer to Earth and thus gain earth observation capability.

    Even if rendezvous were only possible 12+ years later, or not possible at all, we’d still gain data as to their makeup, prove out navigation systems, and suchlike. (I’m very interested in data on fast rotators)

    An inner solar system explorer such as described might also find more Apoheles ( )

    Last I remember 70 were speculated to exist. They are hard to spot from earth, and some may be classifiable as PHOs.

    Has anyone run the numbers for rendezvous or impact on NEOs in resonate near earth objects? (such as cruithne and family? )

    The “foresight” spacecraft design to visit Apophis was pretty interesting and only required a Minotaur IV rocket to get there.

  7. Dave Täht says:

    Hmm… I just looked up the minotaur IV:

    Payload to LEO: 1,735kg
    Cost: 50M


    Falcon9 to LEO: 10,450 kg
    Cost: 50M

    Total cost of the proposed Foresight mission (excluding launch costs, I think): 140m

    Deep impact cost 330m all told. Usefully it has a secondary mission now (EPOXI)…

    I haven’t seen people looking into what they could visit, with low delta-v, after the first target. I remember the hera mission well – 3 rocks in 4 years.

    mass produce a few identical probes, re-use some software, get the costs down and reliability up, keep the mission cycles short, and I daresay we could robotically visit or impact 16 NEOs in under 12 years for a cost of under a billion.

    just sayin…

  8. Joe says:


    The “standard” Orion Vehicle allowed for EVA on an (25 foot) umbillical through the Crew Module Side Hatch (one crew only).

    I have not had time to go though the paper you linked to in detail, but it seems to show multiple crew EVA’s with not only PLSS’s, but MMU’s as well (figure 7 even shows what appears to be berthing stations for the MMU’s.

    Did they discuss any of this at the presentation?



  9. Jonathan Goff Jonathan Goff says:

    They did somewhat. In the presentation (and the paper I linked to), they showed that the shall we call it “Orion Flavored Hab Module” would actually have a hatch with MMU attachment points and some other features on the outside. Basically when it doesn’t have to reenter, and doesn’t have to handle abort loads, but uses the same basic component set and fabrication techniques, you get a lot of flexibility in what you can do.


  10. Nels Anderson says:


    Thinking about it, the NEOs we’re looking for aren’t that cold, so the IR telescope isn’t operating in the far-IR, and keeping things cool isn’t such a big deal. On the other hand, suppose we have a telescope making a Hohmann transfer to the orbit of Venus. If we want to circularize at the radius of Venus, the back of an envelope says that’s a delta-V of 2.7 km/s. The same envelope says that capture by Venus with a pericytherion of 200 km require just about 1 km/s. So even if we don’t hang around Venus, it could be a good place to start.

    BotE says the angular diameters of Venus and the Sun at Venusian L2 (1 million km from Venus) are close: 41′ and 44′ respectively, so to halve the solar flux the ‘scope would have to be within about half a Venusian radius of the Sun-Venus line, i.e., about 3000 km. That does sound pretty tight. On the other hand, perturbing forces must be lower than they are in at Earth L2 (no moon), and maybe (smoking the opium pipe here) you could station-keep by using the sun shade as a sail?

  11. Joe says:


    Thanks. The differences in the Orion and the “Orion Flavored Hab Module” will probably also explain ingress/egress with a PLSS as neutral buoyancy testing indicated that this was tight with just the umbilical


  12. Heinrich Monroe says:

    No, the objects you’re looking for aren’t that cold, but you’re still going to want to survey for them in the near to mid IR. Their energy peak will be around 10-20 microns. Good sensors at that wavelength require cryogenic temps, and are hugely background-limited with a warm telescope/camera. So you still want things to be pretty cold. JWST will be working at those wavelengths, and that telescope needs to be at around 40K to work optimally. That temperature is hard to do passively in a 0.7 AU orbit, but then it’s a small telescope we’re talking about here, and you’ve got loads of power, so an active cooling system isn’t out of the question.

    In fact, to the extent you want to keep stuff cold, and do it largely with shields, you don’t want to be anywhere near Venus. It’s gonna be hard enough to shield the Sun at your back, much less shielding Venus over your shoulder at the same time.

  13. Brad says:

    Interesting stuff. Thanx for your synopsis and the link to the study.

    Two things occur to me. For this mission proposal wouldn’t a modified European ATV spacecraft be a superior mate for the standard Orion, than the heavily modified version of the Orion suggested in the study?
    And since suitable rendezvous targets for an asteroid mission are so hard to come by, why not make it a flyby mission instead?

    A manned flyby asteroid mission could pair with an unmanned lander, with the lander tele-operated by the Orion crew in real time. The lander might even send a surface sample to rendezvous with the passing Orion for return to Earth. Maximize the advantages of crewed and unmanned spacecraft and minimize their disadvantages by co-operative mission design.

    Of course I feel a manned asteroid rendezvous would be preferable to a flyby, but lack of a convenient rendezvous target shouldn’t force us to wait for one. The manned flyby + unmanned lander architecture expands the choice of asteroids we could visit.

    A similar mission architecture could also serve well for a Venus manned mission or early manned mission to Mars. Only short lived robots will ever visit the surface of Venus, and a manned Mars flyby is much much easier than even a manned Mars orbital mission. Experience in a shorter asteroid flyby mission could blend well into follow-on plans for longer flyby missions to Venus or Mars. And a flyby Mars mission could be a smaller step, yet a more immediate one, to the eventual goal of a manned Mars landing.

  14. Robotic precursors to the intended NEO target makes since, but I would feel more comfortable that the NEO also serve as a possible abort site just in case of unforeseen problems.I would preposition items such as a Bigalow station and a prototype Centaur CRYOTE fuel depot before the human mission launches.
    The Centaur would over time produce water, that would contribute to the Bigalow Environmental Control and Life Support System (acronym ECLSS)
    over at Lori Garver’s face book discussion page I have been kicking around a few citizen/taxpayer mission design ideas 🙂 ( and community college student) one of these ideas is that the water from the Centaur (fuel cell) would “inflate” inside the Bigalow a spherical radiation shelter, and would it be possible to integrate into the inflatable walls of the radiation shelter a aquaculture experiment?!/topic.php?uid=109555615732469&topic=275

    ideas on how to use the ULA fuel depot architecture to transport and store cryogenic noble gasses for ion powered in space transfer vehicles! see how I got into deep trouble when I tried to fill up a single tank Centaur with LXe! my whole mission design project fell apart before my eyes.!/topic.php?uid=109555615732469&topic=246

  15. Jeff Wright says:

    Hopkins expressed his doubts about depots as per The Space Review–just Rube Goldberg nonsense.

    Fuel on the ground, keep the LV large, eliminate as many in-space assembly/docking/refueling missions as you can.

    “At $30,000 per kilogram of propellant, it would cost over $2.5 billion to refuel each lunar mission, or $5 billion per year to perform the intended two missions per year. That’s more than the predicted annual cost of the Ares program or some of its heavy-lift competitors”

  16. Jonathan Goff Jonathan Goff says:

    Yeah, I have an ongoing but friendly disagreement with Josh on depots. I think he was raising honest questions, but I also think there are better ways of doing things than what he suggested. In his paper, he suggested using the COTS vehicles, at COTS prices to deliver propellants. That *is* one way of doing it, but was likely a pessimistic worst case. If you assume depots have to be done that way, then yes I’d probably come to the same conclusions as Josh. But I don’t think that’s the only or best way to do things. And quite frankly, I think Josh’s goal with his article was to get depot supporters to better articulate how their depots would operate in a way that actually makes economic sense.

    I do have a lot of thoughts on how to improve on Josh’s example, and at Altius we’re actually working on a key part of that solution now. Ultimately though, while you can put off learning how to do depots, so long as you set your beyond earth orbit expectations low enough, at some point you’re going to have to learn how to do them. And learning how to do them well can greatly accelerate the pace of human exploration and development of space.


  17. Jon,
    A ULA fuel depot tanker that also has a cryogenic Noble as a fuel source might work, IE the tanker is also a ion tug.The tug is the servicing vehicle.In the case of the Iridium constellation there is not any synergy with the ULA fuel depot system in that those satellites do not use cryogenics.
    Kutter 2010 admits there is a weak case for fuel depot DOD servicing missions as a part of a fuel depot architecture,But I am convinced some day fuel depot technology can be used for dual purposes.
    perhaps, such a dual use can be found in a common architecture (ULA)using LH,LO2,LXE,LAr, but my personal trades as a community college student tells me that we are back to the early Kutter paper(2005) that first mentions long life cryogenics as interplanetary transfer stages, and this seems to infer a third stage.
    A second and third stage with cryogenics makes since if one or the other is only LH and LO2 and the other is liquid Noble + NEXT ion engines, that makes since for a science mission if the third stage spends most of its time close to the sun ( solar electric) but many science missions designs do not work out well for ION NEXT engines pushing liquid noble( my best guess ?) using solar arrays for power.

    I suggested on Lori Garver’s page that, a deep space probe utilizing a aerocapture architecture would imply that the spacecraft might have its solar array/RTG and communications devices stowed under its aerocapture shield,An long lived Centaur with a fuel cell and perhaps a solar array could allow fuel depot architecture to enable a Uranus or Neptune aerocapture mission.
    this idea was inspired by the LCROSS mission and the ACES/ULA ideas,
    one more idea over on Lori Garver’s pages, I suggested that the outer planets Centaur upper stage would, just before spacecraft separation at Neptune orbit insertion,perform a avoidance maneuver and perhaps perform a LCROSS type mission(at Tritan?)

  18. Jeff Wright says:

    Enough with the depots already. All this talk about aerocapture, repeated dockings boil-off problems. Just make the rocket bigger, fuel all at once and go. Now you might remember that it took the UR-500 Proton (the Mir space station launcher sold as an uber-ICBM by Chelomei that now has a second life as a comsat launcher what with the giganitism of those spacecraft) to place a rover on the Moon. Mars was simpler in that you could make the rover the heart the actual spacecraft, put it atop a aeroshell, and let Mars run into it, since Mars has an atmosphere. Now a Europa lander has to burn all the way down as a lunar rover would have to do, and is farther from us than Mars. Carolyn Porco supports larger LVs, and if we want robust outer planet landers and what not–it is just easier–and cheaper– to limit all the assembly/refueling nonsense. You are making things harder than they need to be. JIMO, future manned Mars craft, all benefit from having HLLVs that have engine out capability, and yet throw less engines away per 100 tons of payload. Last I heard five or six RS-68s cost less than 21 Delta IV cores and their engines. Josh was dead on in explaining the fact that EELV assembly is MORE expensive than heavy lift. It certainy puts the kibosh on all the Rube Goldberg work-arounds that intoduce more more points of failure in the fault tree. Why people can’t get that in their heads is beyond me. And if Musk really CAN make an HLLV for the cost of Delta-IV heavy or therabouts as he claims, then the case for heavy lift just got better, especially as EELV costs are going up.

    I liked Griffin better than you lot do, for several reasons. To start off with, I’m not a libertarian. I prefere things be done in the arsenal method, in-house, with contractors on the short leash. I also understand that solid rocketry has to be considered a national asset, so I will side with ATK over ULA every time. Lastly, NASA should be independant of USAF/DoD pressure, since they would have loved to offset LV costs on NASA if they could so as to keep fighter-jocks and the like happy–so as to avoid any aircraft development cuts down the road.

  19. Jonathan Goff Jonathan Goff says:

    Thanks for sharing your opinion. You’re definitely entitled to it. It’s wrong, but it’s ok to be wrong some times. 🙂

    Seriously though, if we as a nation care about manned spaceflight as anything other than government subsidized entertainment, we’re eventually going to have to put on our big-boy underpants and learn how to actually function as a spacefaring society. Because, long before you’ve gotten out of the “astronauts as the functional equivalence of firing clowns out of cannons” phase, you’re going to run into missions where it isn’t possible to just build a bigger rocket. Even going to the moon in a way that isn’t just expensive stunts is going to outgrow the biggest rocket you can realistically build at KSC. You’re going to have to do multi-launch architectures, so why not do something efficient? Why not do something in a way that actually enables mankind to do more in space, more cost effectively etc.?

    Your arguments to me are uninteresting because I don’t consider an HLV-derived stunt program as something worth $10B year. It isn’t a space program worthy of a great nation. At least, not one in this century.


  20. Jeff Wright says:

    It isn’t a stunt program. The shuttle is an HLLV after a fashion–it is just that most of the mass is locked up in the orbiter. We have shown wirth STS that this nation is capable of launching HLLVs for decades, and none of you comments above have adressed the problems I have pointed out. Had those launches been with space-only payloads, humanity would have a lot better on-orbit presence.

    My arguements are uninteresting to you the way Sea Dragon was uninteresting to NASA back in the day. Buildings, Dams, oil rigs–all of these structures have grown and yet we stagnate with the 20-ton-and-not-an-ounce-more-to-orbit. The laws of physics still apply in this century the way they did in the last. Just because something looks sexier doesn’t mean its better–Like STS. At least the Energiya Buran concept was to be a true space transportation system, with EELV class strap-ons an HLLV and an orbiter if that is what you want. Sadly, the Soviets wasted a lot of money in occupying muslim countries and getting bogged down with the Baikal Amur Mainline. Here Obama wants to force the USA workers into high speed rail, and yet we still occupy the same nation as did the soviets.

    What is ironic in all this is that many in NASA wanted to keep the Saturns, and the whole segmented solid support was for the USAF’s Titan augmentation. Had we ignored the folks wanting sexy reusable spaceplanes and kept the Saturns–we would have been better off.

  21. Brad says:

    No love for flyby? That makes me sad:-(

    Merry Christmas and Happy New Year!

  22. nooneofconsequence says:

    Fascinating to see prop depots linked with libertarian politics, as I just got back from a meeting where the topic of authoritarian vs libertarian as a description of the social structures internal to aerospace – never occurred to me to think of this as important as it appears to be. In this conflict, the authoritarians are slowly losing (at the moment) …

    Did enjoy the paper.

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