16 thoughts on “Launch-System Reusability”

  2. Shhhh…if we keep quiet, XCOR might make it big.

    Thomas Matula made a good point over on the linked site:
    “One of the unfortunate legacies of Project Apollo and the Shuttle is the belief that progress is only possible in the limelight. Real technical innovations, like the Internet, comes far more often from outlying projects, ones few are aware of until they reach the maturity to take over from the status quo.”

  3. Don’t expect a reusable launch vehicle out of NASA or DoD. As long as they are specifying things, the payload requirement will always drift up to 60,000 pounds, which will always kill the program.

  5. Don’t expect a reusable launch vehicle out of NASA or DoD. As long as they are specifying things, the payload requirement will always drift up to 60,000 pounds, which will always kill the program.

    Seeing as how the DoD has some really large payloads (e.g. that NRO bird launched out of Vandyland on a Delta IV Heavy recently), then they have a valid need to push the lift requirements to be sufficient to carry the things they need to carry. To do otherwise would be rather foolish, like specifying a transport airplane that’s too small to carry standard military payloads.

    Now, if they kept the odd expendable for those really big things and defined the requirements for a reusable to something more manageable, say 10 metric tons to LEO, then a reusable becomes a valid option.

  6. “Seeing as how the DoD has some really large payloads…”

    NASA has a REALLY large payload in orbit right now, the ISS. It weighs 828,000 pounds. Now let’s see, what was the one single rocket that launched it? Hmmm, I can’t seem to bring it to mind at the moment.

    It would make a lot more sense to build really big spacecraft in space, rather than on the ground. The need for heavy lift goes away. So does the need to build and qualify a spacecraft to withstand the rigors of launch, and the need to test the spacecraft in a simulated space environment (since the real one is right there). An orbital infrastructure consisting of a barracks and a hangar would support this. If the whole thing is built to be serviced by a rather smallish RLV, the flights would be frequent and the costs would go down.

    The U.S. could retake the GEO comsat market, as well…

  7. they have a valid need to push the lift requirements to be sufficient to carry the things they need to carry

    Let’s say half could fit on a reusable and half on an expendable. Would they then forgo the half that could to work on something that works for none?

  8. It would make a lot more sense to build really big spacecraft in space, rather than on the ground. The need for heavy lift goes away.

    Some things like the ISS are modular and can be assembled in space. Other things are tightly engineered to be a single entity and require precision assembly that would be difficult to do in space. Consider the Hubble Space Telescope. They had enough problems building it on the ground and still messed up the primary mirror. Imagine trying to launch it in pieces and assemble it in space. Not exactly easy. Now, consider a large optical photographic reconnaissance satellite. It has more complexity than the HST and is in a sun synchronous orbit that’s not exactly easy to reach with a crewed vehicle.

    About the best you could do with such a payload is to launch it with almost empty propellant tanks and then use a reusable vehicle to fuel it on orbit.

  10. “Some things like the ISS are modular and can be assembled in space. Other things are tightly engineered to be a single entity and require precision assembly that would be difficult to do in space.”

    This misses the point in several ways. 1) Everything built from parts is “modular.” The definition of what constitutes a module changes. 2) ISS was as “tightly engineered” as any communication satellite — more so, in at least one respect. Interface control was more stringent than it is in a satellite built in one house. 3) Most of the “tight engineering” of a spacecraft launched from the ground is driven by: folding a big spacecraft into a small fairing; making sure it can survive the dynamic environment of launch; and then making sure it can unfold into a big spacecraft again once it is in space. A spacecraft built in space would look completely different from one built on the ground, then launched as a whole. Witness the ISS…

    As for screwing up the mirror on Hubble, I wasn’t suggesting that one grind a mirror in orbit (the Hubble mirror was ground incorrectly). But assembling a segmented mirror telescope in orbit would be less challenging than doing so on the ground, in many respects. And if one found that the segments were ground incorrectly, one could send up new ones. The entire “mission” would not be jeopardized.

    As for changing orbit planes, that can be done over time with high Isp solar-electric propulsion. I wouldn’t propose a manned polar factory.

  11. they have a valid need to push the lift requirements to be sufficient to carry the things they need to carry. To do otherwise would be rather foolish, like specifying a transport airplane that’s too small to carry standard military payloads.

    Interesting comment because, oddly enough, some military leaders proposed such “foolishness” at the outset of World War II.

    The existing commercial off-the-shelf transport (called the DC-3) was clearly “too small to carry standard military payloads” — despite outlandish suggestions from Douglas Aircraft that the plane could carry barrels of oil and gasoline, prefab buildings, pierced-steel plate runways, livestock, even complete fighter planes with the wings removed and slung underneath the fuselage.

    The United States needed to build a network of bases and fuel depots all across the Pacific, each one of them larger than the International Space Station. Assembling all those small payloads in the field was an obvious impossibility. It would require an army of soldiers performing millions of hours of extravehicular activities under extremely hostile combat conditions.

    So the Army commissioned Howard Hughes to develop the Spruce Goose, contrary to the thinking of “fools” like Dwight Eisenhower who called the DC-3, along with the Higgins boat, the bulldozer, and the 2.5-ton truck (all of which had clearly inadequate cargo capacity) the “four machines that won the war.”

  12. Consider the Hubble Space Telescope. They had enough problems building it on the ground and still messed up the primary mirror. Imagine trying to launch it in pieces and assemble it in space. Not exactly easy. Now, consider a large optical photographic reconnaissance satellite. It has more complexity than the HST

    Hm. I wonder how the Keck telescopes (larger and more precise than the Hubble or any recon satellite) got to the top of Mount Mauna Kea?

    Surely, they couldn’t have been trucked up a piece at a time and assembled on site?

    No, that would be as foolish as building the mirror in segments.

    and is in a sun synchronous orbit that’s not exactly easy to reach with a crewed vehicle.

    I don’t know what makes you think that. Both NASA and the USAF had plans to conduct Gemini missions in sun-synchronous orbits. In the early days of the Shuttle program, the Air Force built a launch pad at Vandenberg AFB for launches to sun-synchronous orbit. It was intended mainly for military flights but NASA contemplated using it for Landsat launches as well. MSFC even proposed a crew-tended science platform in sun-synchronous orbit.

    Just because something hasn’t been done doesn’t mean it can never be done — and just because a requirements document says something should be done one way doesn’t mean it’s the only way it can be done.

  13. As for screwing up the mirror on Hubble, I wasn’t suggesting that one grind a mirror in orbit (the Hubble mirror was ground incorrectly).

    To be more precise, the mirror was *specified* incorrectly — the guys on the shop floor ground it correctly according to the specifications.

    Whether a telescope is built on Earth or in space, the specifications for it are going to be written in an office on Earth — at least, for a long time to come.

    Launching satellites in one piece has not prevented specification errors in the past. It won’t prevent them in the future.

  14. “To be more precise, the mirror was *specified* incorrectly — the guys on the shop floor ground it correctly according to the specifications.”

    No, it was ground incorrectly because the instrument which measured spherical aberration had been assembled incorrectly, and was giving bum readings. There was nothing wrong with the specification of the mirror.

  15. All I’m saying is that some things lend themselves to being broken into smaller pieces and assembled in orbit while other things don’t. Those things that don’t are the ones that drive your toughest requirements and no amount of handwaving or PowerPoint engineering can do away with that.

    As for changing orbit planes, that can be done over time with high Isp solar-electric propulsion. I wouldn’t propose a manned polar factory.

    This is an example of what I’m talking about. Sure, you can change inclination using ion thrusters but in the case of most sun-synchrounous orbits, that could take months to years. Not exactly responsive from a military standpoint.

    The existing commercial off-the-shelf transport (called the DC-3) was clearly “too small to carry standard military payloads” — despite outlandish suggestions from Douglas Aircraft that the plane could carry barrels of oil and gasoline, prefab buildings, pierced-steel plate runways, livestock, even complete fighter planes with the wings removed and slung underneath the fuselage.

    And while the DC-3/C-47 was a widely used workhorse, it wasn’t the only cargo plane used back then. For heavier loads over longer distances, the USAAF also had planes like the C-46, C-54, and C-87. Not long after the end of WWII when the Soviets blockaded Berlin, transport planes from all over were used in the Berlin Air Lift. Once things were up and running, they stopped using the DC-3/C-47 because it was too small and inefficient to meet the airlift requirements. It took as much time to land one of them as it did a larger plane and they just didn’t carry enough payload to do the job.

  16. All I’m saying is that some things lend themselves to being broken into smaller pieces and assembled in orbit while other things don’t.

    I can’t see any argument to that, but when designing something it makes sense to try to use existing capabilities rather than adding the additional requirement of a new launch system when possible.

    Existing capability allow for some pretty big parts. Plenty for large Lego pieces for quick assembly.

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