Tuesday, September 27, 2005

LH2: Love it or hate it?

Jon Goff has an absolutely fantastic post here at LH2: Love it or hate it?

LH2 seems most clearly stupid for a first stage fuel. Hydrogen engines have low thrust-to-weight, low thrust-to-cost, and big tanks which can cause a lot of atmospheric drag. Hydrogen first stages also see larger gravity losses than hydrocarbon first stages.

Both the Shuttle and the Delta IV use LH2/LOX engines off the pad. The Shuttle uses hydrogen because those engines are ground-ignited second stage engines, so it has at least some excuse. But the Delta IV is a simple two stage rocket with both stages being LH2/LOX. Why? Did they need to be different than the Atlas V?

Thursday, September 22, 2005


I just read a fantastic article in The New Republic. In it, Husain Haqqani & Daniel Kimmage comment on a series of 430 short biographies of Iraqi insurgents. At the end, they have a suggestion I really like:

Imagine how the biography of the "hero" Al Shammari would read if it were juxtaposed with the biographies of the people he killed? What might readers in Saudi Arabia, Syria, and elsewhere in the Arab world make of a companion volume to "The Martyrs" in which each suicide bomber faced his victims, not as statistics in a war against the infidels, but as individuals in their own right?

Friday, September 09, 2005

Falcon 9 Upper Stage Recovery

The SpaceX annoucement is fluffy. Their big engine is late, and they're going to try to push their Merlin 1 based product a bit past its economic sweet spot.

Significantly, SpaceX has not specified the upper stage. The upper stage for a plain Falcon 9 to LEO lift will require at least two and perhaps three Merlin engines. The upper stage for a Falcon 9-S9 to LEO lift (required to deliver a Space Shuttle cargo to the ISS) will require at least five Merlins, which means it will actually be a Falcon 5 first stage, but with large expansion ratio nozzles and some ability to do in-space restarts (propellant settling, multi-use igniters, RCS without gimballing the main engine). If they are going to recover that stage, though, they'll need more than just the F5's parachutes, they'll need some really wonderful ablatives, somehow spread under all the delicate engine bits.

If you ignore the upper stage reuseability, the business scheme seems wonderful. NASA needs 20+ heavy LEO launches to lift the rest of the ISS. SpaceX builds a fleet of identical airframes and engines. Four airframes and 32 engines go up, three and 27 come back. They build about 25 airframes and 140 engines over several years, and each airframe gets an average of three flights, and each engine gets four or five. They might charge NASA $1.5B for the whole launch set and make a ton of money, and save you and me (i.e. the average taxpayer) about 75 bucks apiece.

But what's this about Full reuseability? Full reuseability is not a press mistake. The SpaceX press release says explicitly that

Falcon 5 and Falcon 9 will be the world's first launch vehicles where all stages are designed for reuse.

(Except Kistler's design, of course.)

This is crazy. If they take over lifting the ISS segments, they'll have a nice steady stream of launches. Over time, they're going to learn how to manufacture their engines better (more thrust, better reliability, lower manufacturing costs), and the later engines will be better than the earlier ones. The steep learning curve makes the early hardware depreciate fast, which makes spending more money to recover it less attractive. Throwing away the upper stage is a great way to clear out the obsolete inventory.

Heck, at some point (2007?) they're going to deliver the Merlin 2. My guess is that this will be a 600,000-lbf-thrust engine. Their next-gen EELV-class launcher will lift 25,000 kg to the ISS without strapons, with four Merlin 2's as the bottom stage and four or five Merlin 1's as the top stage. Why use the Merlin 1's in the upper stage? Because their business plan requires each engine to get used a bunch of times. The last thing they want to do is introduce a new rocket which obsoletes $60 million dollars worth of engine inventory. Instead of recovering a brand-new engine from the upper stage, it will be cheaper for them to use and expend their Merlin 1 inventory in the upper stages of their launches.

I bet the upper stage reusability verbiage is just there to appease some group at NASA. SpaceX may actually attempt a controlled upper stage reentry with ablatives when launching some slightly more lightweight ISS segment. They may get some interesting data from such experiments. But I can't see them pushing upper stage reuseability very hard. They need to concentrate on the easier and more lucrative problem of recovering their lower stages first.

My Own Vision for Space Exploration

Since I think Bush's Vision for Space Exploration is screwed up, I thought I'd offer my own.

Unmanned exploration

I would initiate a steady program of planetary probes, a common interplanetary communication system, and space-based observatories.

Budget: $4B/year for about 6 probes a year over 2006-2016
about 30 heavy and 30 medium launches
Budget: $8B for 3 observatories over 2009-2016.
about 10 heavy launches

Exploration infrastructure

Most probes are limited by their ability to transmit data back to Earth. That ability is limited by the power available to transmit. For the planets beyond Earth (or perhaps Mars), power is limited because solar cells do not have significant yield. I would fully fund the Prometheus project, which is developing a small nuclear reactor for use in space.

Beyond finishing the development of nuclear reactors in space, existing technology is already comfortably close to the limits of what can be transmitted for a given amount of power. It makes sense, then, to have multiple probes in close proximity use the same communication system. This is already done to some extent at Mars, with Mars Odyssey and Mars Global Surveyor relaying signals for ground rovers.

I would initiate a program to launch a nuclear-reactor-powered long-range communication satellites into orbit around each of Venus, Mars, Jupiter, Saturn, and Uranus, and (probably) one roving satellite in the asteroid belt. These satellites would primarily be responsible for relaying high data rate bit streams to earth from local probes. They would be built for a useful lifetime of 25 years. They would also carry a modest scientific payload.

Budget: Prometheus: $4B over 2006-2010
Budget: Comsats: $12B for 6 comsats over 2011-2016
about 20 heavy launches

Orbital Assembly Development

Observatories and comsats, and to some extent probes, have one thing in common: very large communication dishes or imaging reflectors. Observatories and especially the extraterrestrial comsats will also be very heavy. All of these missions can benefit from orbital assembly. I do not forsee intricate assembly of the sort requiring people, nor do I see the ISS as a good place to do this assembly, as it will likely involve close proximity to very large amounts of propellant. I would fund one assembly robot in low earth orbit.

Budget: $2B for one assembly robot over 2006-2010.
2 heavy launches

Transportation development

The extraterrestrial comsats in particular and long-range probes in general have large propellant requirements. To avoid the need for seldom-used massive launchers and their infrastructure, these probes should be boosted to their destinations by the same stage that put them into low earth orbit, but refueled in orbit by other rockets, so that multiple launches can assemble the mass to be launched out of LEO.

To help the nascent boost industry, NASA would be required to fit all payloads into the standardized EELV payload masses and sizes. Payloads intended to fit in the Shuttle for ISS delivery will fit into Heavy EELV boosters.

The Shuttle program would be summarily dumped. If ATK thinks that solid rocket boosters are a good match to LEO delivery (as they may well be), they are welcome to collaborate on an EELV booster to compete with the existing 2 (Delta 4 and Atlas 5) and potential 1 other (Falcon 9).

NASA would develop a Crew Transfer Vehicle. This vehicle would be a capsule carrying about six that would ride as one of the smaller EELV payloads (perhaps the 9000 kg class). If t/Space thinks they can drop-kick people to the ISS for less money, I'd entertain a proposal.

Budget: $2B over 2006-2008 to develop the CXV.

Manned spaceflight

The International Space Station would be completed with EELV Heavy launches over the next several years.

Budget: $4B over 2006-2010 (just for cargo launches)
about 20 heavy launches (ISS segments cargo only)

As well as assembling the station, crews would be sent up fairly often to perform science experiments.

Budget: $1B/year over 2006-2016 (just for the launches)
5 medium launches per year.

Manned exploration

There isn't going to be any of this in the next 20 years. Instead, NASA would spend some portion of it's budget learning how to live, work and do science in space. In the meantime, all the probes launched would find out what we actually want people to look at.

Budget: $2B/year over 2006-2016


My total yearly budget ends up about 70% of what NASA spends today. Probably I have no idea how much things cost. In particular, I left out ISS operational and future segment build costs.

I don't see any massive increase in the launch rate. Over the next
11 years, I see about 160 launches with a total price tag of about
$12B. A billion dollars a year seems like enough money to keep
perhaps two players going -- with just 1000 employees each.

Heavy: 82 @ $100M/each
Medium: 80 @ $ 40M/each

Thursday, September 08, 2005

SpaceX choices

SpaceX has just announced a new, bigger launch vehicle. It has a number of configurations, some of which are roughly the size of some of the Evolved Expendable Launch Vehicle (EELV) sizes. The EELV program was a Defense Department-funded program to develop two launch vehicles independent of the Shuttle for military payloads, started after the Shuttle fleet was grounded after the Challenger accident.

Q: What is the Falcon 9 intended for?

A: The Falcon 9 is intended for three missions:

  • Steal payloads from the other two EELV boosters: Delta 4 and Atlas 5. These payloads are mostly military, and the Pentagon would very much like to have a reasonable fallback if they have to cut funding to one of the two subsidized EELV launchers. The Pentagon likes this idea so much they are spending real money on it: Falcon 9's first launch is a defense department satellite.

  • Replace NASA's "Stick" booster.

  • Lift the remaining ISS sections.

    Q: Why has SpaceX announced Falcon 9 now?

    A: SpaceX wants to stick a crowbar into the public debate over NASA's two new boost vehicles. I'm sure the competing camps at NASA have been fully aware of SpaceX's Falcon 9 plans for a while, and probably driving them to some extent. But NASA's decisionmaking is not entirely internal -- they have to convince policymakers to fund their plans, and quite a lot of that convincing is done by attempting to frame the public's perception of those plans.

    The ATK/Morton Thiokol lobbyists, and their camp within NASA, have been pushing two new mostly expendable launch vehicles, one to launch a 21 - 26 metric ton crew capsule and resupply ship to the International Space Station, and one to launch Very Heavy Things (110 metric tons) needed for manned lunar or Mars expeditions. Both would use solid rockets derived from the Shuttle SRBs. The big launcher might throw away four reusable SSME engines per launch, which is expensive.

    The push isn't going well right now. Developing two vehicles will cost more than NASA is spending now, and that looks very bad to legislators spending hard-won tax dollars on the non-pork-barrel Iraq war and the $700 million/day cleanup of Katrina.

    Jumping into the fray now lets SpaceX grab some of the public's mindset before it gets solidified by the ATK camp. They have a launch coming up soon. If it succeeds, John Q Public is going to wonder why NASA can't use the reliable SpaceX booster instead of developing a nearly brand-new launcher.

    NASA's designs for a Shuttle-derived Shuttle replacement center around the idea that the technology development, supply chains, and infrastructure it has developed for the Space Shuttle are valuable in their own right. Because the Shuttle is nearing retirement, all three of these things are in danger. For instance, if there is no future vehicle to use a Shuttle/SRB-like solid rocket booster, ATK will have to shutter its plant for assembling these monsters. NASA is absolutely right in realizing that a unique capability that only exists within the U.S. will vanish if that happens.

    But the hard question is: are those capabilities actually useful? The ATK boosters, for instance, produce 3.3 million pounds of thrust each, and cost about $40 million per launch. A simplistic analysis of SpaceX's launch prices put an end-user cost of $2.25 million per launch on each Merlin engine, each of which produces 85,000 pounds of thrust. The solid rockets are a much better deal for straight liftoff thrust, at $12.12/pound rather than the $26.47/pound of the Merlins. (The price difference is mitigated significantly but not reversed by the better Isp of the Merlins.) The as-yet-unfulfilled promise of SpaceX is that they are going to recover their engines or even most of the vehicle after each launch, and then will reduce their prices. And, of course, prices in the launch market are flimsy: I read wildly different estimates for costs and have not done my own accounting of NASA's costs, which I assume are public record.

    I think the SpaceX entry is great for SpaceX. I had lamented earlier that the Falcon V was just not big enough for ISS resupply. Falcon 9 solves that. This gives SpaceX an obvious and fairly large launch market (I'm guessing three-plus launches a year), which should give them an operating profit with which to fund future development. It should also give them a launch history. It's up to them, of course, to make that launch history one to be proud of.

    One hopes that launch market is also an elastic market: since SpaceX's prices are quite low, NASA might get to eventually rotate more of its astronauts through the ISS and actually do some science up there.

    I think the SpaceX entry is great for NASA. It gives them the excuse to retire the Shuttle early. It gives them a cost-effective way to assemble the ISS without the Shuttle. With some foresight, they may be able to focus on the in-space aspects of putting people on the Moon or Mars instead of spending all their money on ground handling of launchers.

    Lingering problem #1: How does NASA kill off the Shuttle-derived Heavy Launcher? NASA's standing army can't be dismissed until that thing is dead, gone, and maybe replaced. Or perhaps, the folks at NASA will let go of the need for big heavy launchers. I can see this happening for missions with large fuel requirements (launch the fuel seperately).

    Lingering problem #2: SpaceX needs to launch a bunch of Falcon 9s before anyone should be confident that they are safe enough for people. What are they going to launch? Possible answer: ISS cargo-only resupply missions. Stretch goal: launch astronauts on Soyuz, and launch ISS sections on big Falcons. It might take a lot longer to assemble the ISS with just 4 people on board, but it might still be doable.

    Finally, SpaceX's F9-S9 launcher has no less than 27 2.25-million-dollar engines at the bottom, and their launch prices are about $3000/kg to LEO. Maybe those engines are going to get cheaper if they start cranking them off the production line. But it seems to me SpaceX needs a bigger engine (and a larger diameter standard fuselage), because the current scheme isn't going to scale up much larger. Elon Musk promised that such an engine is in development, but it must not be well enough developed to enter into the current debate, as SpaceX is going to have enough difficulty getting credibility for even the Falcon 9. SpaceX development is late, and they are starting to reap the costs of being late.