Tuesday, May 31, 2011

End of May Update

My Mars mission study has been accepted for presentation at the Mars Society convention in Grapevine, Texas, August 4-7 this year. I will barely be back on my feet after knee surgery at that time, but I wouldn’t miss this meeting on a bet. The basic study was posted here 12-20-10, with an update posted 1-8-11, correcting an error I made in a Falcon-9 payload number.

All of the launcher and capsule data I used were obtained from the Spacex website for 2010. Sometime after January 2011, Spacex updated these data, showing a significant increase in payload capacity estimated for the Falcon-9-heavy, which is now supposed to fly for the first time out of Vandenburg late this year. That change just makes my design even more cost-effective, but I am not going to change my presentation because of it.

I did a little nontraditional thinking, dominated by crew safety, and came up with a tremendous science return for a lot less investment than anyone will likely believe. This is way more than “flag-and-footprints”. You never know what you can do until the blinders come off. It is going to be a lot of fun.

Latest news releases in AAAS’s peer-reviewed “Science” journal confirm everything I posted here about the nuclear plant disaster in Fukushima, Japan. You have to go inside the reactor building ruins before you find radiation too dangerous for adult humans, and then it’s just barely enough to cause prompt radiation sickness. The whole argument over risk to the Japanese public seems to center on the putative risks of very low-level exposures. With no evidence to support or deny a very slight risk of slightly-above-background-level exposures, it seems rather silly to worry much about it.

Now that the Mars mission study is done, and I will be off for a while with the knee, I can return to the question of ramjet-assisted launch. I’m pretty sure that horizontal takeoff with a two-stage vehicle is feasible with simple parallel-burn rocket and ramjet in a winged first stage. I’m pretty sure the staging velocity can be pushed to right at Mach 6 with a simple subsonic-combustion hydrocarbon-fueled ramjet. The upper stage rocket can be either winged or plain gravity-turn ballistic, as desired. To hit Mach 6 staging, a spike inlet will be required, which pushes practical takeover velocities to around Mach 1.5. Parallel-burn can be used right at staging to achieve path angle. I think the staging altitude is probably closer to 60,000 feet than 80,000 or 100,000 feet altitudes. That study needs a rerun with a resized engine and revised staging altitude. The earlier versions were posted here last year.

I don’t know yet whether ramjet assist is beneficial for a vertical-launch gravity-turn staged vehicle. But, if it is, it will be leaving the sensible, usable atmosphere closer to Mach 2 or 3 speeds than Mach 6. That’s a lower-speed ramjet design, most likely a simple normal-shock (pitot) inlet and a simple convergent-only nozzle. Takeover will likely be at slightly-subsonic to merely-transonic speeds. I have most of the guts of a sizing and performance code programmed, but it still does not quite work right in performance mode. Maybe I’ll have a chance to work on that while recuperating. Properly sized with an appropriate integral booster rocket, this kind of ramjet would be a strap-on staged off substantially earlier than the typical first stage burnout, in a two-stage vehicle. But it just might help.

Watch this space for future postings.


  1. Hey GW, I'm glad to hear that you're still keeping up your work on all of this stuff, and space missions in general. I'm definitely going to go take a look at that mission proposal. I also absolutely agree about the Fukushima thing, fears of the radiation release were way overstated, and it would be much more productive to focus on the (hundreds of?) thousands of people who have been displaced and injured by the tsunami.

    Anyway, I'm Josh. You probably know me better as Jumpboy11j form the Newmars forums, which crashed in January and there have been some issues bringing them back up. Anyway, we're kind of regrouping for the moment at the wiki http://newmars.wikispaces.com/ , where you'd be plenty welcome. At the moment the basic point of the wiki is to try to reconstruct things which you want saved from the forum, because it is starting to look like we're not going to get a lot of the posts back, though new ideas are of course always welcome. Anyway, hope to be seeing you there and best of luck at the conference!


  2. Josh:

    Good to hear from you! I'll go look at the wiki thing, although I am a novice at such things (I can barely post things here). I'll be posting an article here "soon" that is the exact content of the presentation in Dallas in August.

    It'll be few days before I get anything done, though. I'm going in for knee replacement surgery before dawn Monday 6-13. I'll get the presentation and the paper done while in rehab.

    -- GW