Skylon is what we should have built over the last 20 years instead of the existing space station. Could have used international partners, would probably be back on the moon by now an working to assemble the Mars rocket. Why couldn't we use the empty Shuttle tanks and open one end for assembly or have it pressurized to work in shirt sleeve environment, then open the end to let out an assembled spacecraft?With small rockets, one would need to develop a small nuclear engine capable of shuttle between Earth and Moon and then to mars.
A crewed Mars mission is impossible with a 5M fairing even with inflatables the aeroshell just will not fit.
Quote from: Patchouli on 10/16/2009 02:05 amA crewed Mars mission is impossible with a 5M fairing even with inflatables the aeroshell just will not fit.This is a myth. You don't need large payload fairings for Mars missions. You probably do need inflatables. With Mars the problem isn't descent but ascent. Bringing all your propellant with you would be prohibitively expensive. You would need ISRU for your ascent propellant, perhaps just on Phobos/Deimos, but probably on Mars itself.
If you're going to rely on ISRU for all your fuel, you can do a fully propulsive descent with your Mars ascent vehicle. No parachutes, no heatshield, no skycrane, etc.
-No space mission can go with 90% of it's peices. An HLV mission delivers 50-100% of the mission in 1-2 shots. The mission has a much more up or down launch success rate. The only way you waiste both halves of the hardware is if the 1st launch is a success and the second is a failure. All other situations you have either complete failure or success.If you split your exploration mission into 4 pieces and the 1st 3 are successful, but the 4th fails, it's a LOM. 6 pieces and 1 failure LOM. All modern LV are 95%+ reliable, whether they are small or large. Small LV make your role the dice more.
Quote from: Hop_David on 10/14/2009 09:25 pmIs it possible to bust Apollo into enough chunks that each chunk can fit under the fairing of a Falcon 9? Or a Falcon 9 Heavy?Of course it is. But possible and optimal sometimes don't see eye to eye. Some fun facts to remember when talking about the idea of large missions into small pieces.
Is it possible to bust Apollo into enough chunks that each chunk can fit under the fairing of a Falcon 9? Or a Falcon 9 Heavy?
-Unless using a VERY advanced tug, that has never been built,
each piece will have to have it's own avionics, thrusters, and docking mechanisms. If using a 20 MT launcher, that' 25% of your launch weight just to attach to the other pieces.
-If launching all peices from one pad you will have a significant loiter time on your components. If you use multiple pads you save on loiter time, but add new LOM possibilities due to pad delay.
I support the idea of the Medium lift exploration system, it allows more balanced international cooperation, lower development costs, more immediate milestones, possibly lower costs, and greater synergy with commercial launch. It's just not a panacea.
Mars launch window lasts a couple of months, no? At this stage of the argument Zubrin's ERV has been busted into 6 chunks. How difficult is doing 6 launches in two month's time?
If you have loiter time how about 6 launches in 6 months. Much easier to manage. Only the astronauts from Earth and departure from LEO needs to be in the 2 months window.If you have 6 months to assemble the spacecraft there is time for a 7th launch to replace any component whose LV failed.
Why are we assuming the TMI is done from LEO? Using L1/L2 is much easier, especially with small rockets.
Quote from: A_M_Swallow on 10/17/2009 08:12 pmIf you have loiter time how about 6 launches in 6 months. Much easier to manage. Only the astronauts from Earth and departure from LEO needs to be in the 2 months window.If you have 6 months to assemble the spacecraft there is time for a 7th launch to replace any component whose LV failed.The payloads destined for Mars surface loitering in LEO would need enough propellent for 8 km/sec delta V, I believe.How would you power the refrigeration units on the Lh2 tanks for 6 months? will you have a shield that protects the Lh2 tanks from the sun's light as well as reflected sunlight from earth's oceans?Or would you do separate launches to fuel propellent depots to serve the loitering Mars bound mass?
Part of my motivation for this thread was to better inform myself for a discussion on a New Mars thread Budgeting for a Mission
Some of the people I'm arguing with at that forum adhere to the orthodox Zubrin doctrine that the moon, EML1, etc. are silly distractions. They seem to believe that if we stopped wasting our time and money on such shenanigans that we would be well on way to establishing a self sufficient Martian colony. So I was working within their architecture.
Quote from: Hop_David on 10/17/2009 10:44 pmPart of my motivation for this thread was to better inform myself for a discussion on a New Mars thread Budgeting for a MissionThanks for that link, I'll go have a look.
In my view if you can't do long term cryogenic storage and cryogenic propellant transfer, you have no business going to Mars.This should help:http://www.ulalaunch.com/docs/publications/CryogenicOrbitalTestbed(CRYOTE)2009.pdf"CRYOTE can increase component and system TRL to Level 7."