22 thoughts on “A New Age Of Low-Cost Launch?”

  3. @Wodun, I think the idea is that when the carrier plane gets to the right altitude it drops the rocket like a large bomb. When the rocket falls a safe distance (not much) the motor ignites.

  4. I’ve run a few trajectory optimizations in the past. I will say that they are looking at 29000 fps for low inclination leo, could be more for space station. They said the release mass would be 490 kpounds and the payload would be 13.5 kpounds. I will guess at a vacuum expansion of 320 seconds for the booster and 342 for the second stage. It looks to me that they are way underperforming or that they are putting a lot of mass into the booster and second stage. I will guess the later. I’ve got a staging off booster wt of 80 kpounds and a 2nd stage mass of 8.5 kpounds. That tells me they’re bookkeeping extra structure and propellant for reusability.

      1. The 310 vacuum is predicated on a sea level start without too much atmospheric loss. The regular Merlin is 275 at sea level. I’m guessing by looking at the picture that they they have a much larger expansion nozzle if they are going for a start at 45000+ feet. And the second stage of Falcon 9 is already rated at 342 vacuum start.

  7. Can someone explain to me why it has to take a few days for ground-launched vehicles to rendezvous with ISS?

    I thought I understood orbital mechanics, raising and lowering apogee and perigee, plane changes etc, but I must be naive because I would have thought you could just wait until ISS was approaching for a reasonably overhead pass [1], launch, do a circularization burn at apogee half an orbit later, and find yourself flying parallel to ISS within a couple of hundred km or so.

    [1] looking at http://is.gd/uHcG1D Florida seems to get an ISS pass higher than 70º every three days or so. I don’t know how close to overhead is really needed, but that seems reasonable — it puts the ground track within 150 km.

    1. The Earth revolves. One needs to wait until the Earth’s revolution traces the launch site through the station’s orbital plane. If you are not in the plane, you don’t get to the rendezvous without horrendous extra propellant. You launch in the plane and only in the plane even if the station is on the other side of the world. Then you have to orbit in a lower orbit to catch up or a higher orbit for the station to catch up with you. With air launch, one flies out to the correct plane crossing point where the station will be right there when you achieve orbit.

      1. Yes, that is one reason visionaries like Arthur C. Clarke assumed launch sites would be on the equator, and space stations would be in equatorial orbits, to allow rapid rendezvous opportunities every 90 minutes or so. But nationalism triumphed good engineering principles. Air launch helps to fix the problem of non-equatorial orbits for space stations.

        1. “Nationalism” like equatorial sites being very distant from the countries (and the corresponding industrial base) that happened to be space-capable.

        2. Yes, launching at the equator would be ideal, but looking at Google Earth, there just aren’t many good locations that are exactly on the equator and have open ocean to the east. Brazil, Somalia, the North Moluccas, and perhaps Howland Island. That’s pretty much it.

        3. Equatorial orbits are generally only useful for GEO satellites. For lunar and solar system missions you’d instead want to use the plane of the ecliptic, which is about 23 degrees from the equatorial plane. Since most LEO satellites and space stations are devoted to Earth observation, navigation, and communications, they sweep north and south to get good coverage.

    2. Strictly speaking it doesn’t take 2 days to rendezvous. However, doing it that way is often more convenient. It broadens the launch window on the ground and gives the flight crew and operations team more time to prepare, which is reasonably important for a complex maneuver like a rendezvous and docking.

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