Author Topic: Phobos as a destination - a routemap  (Read 3324 times)

Offline alexterrell

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Phobos as a destination - a routemap
« on: 10/31/2009 09:59 am »
The discussion "Is Phobos a realistic Goal" seems to have the answer Yes.

There are a number of benefits that make Phobos (or Deimos) easier than either the Moon or Mars (though, subject to confirmation by remote probes).

So what could be done?

I though I'd draw up a mission routemap and run some Excel calculations. With Solar Electric Propulsion and ISRU at Phobos, a manned base can be established, supported and expanded with about 6 SD HLV launches per year. This includes Mars surface landings starting in Mission 4 in Year 9.

I enclose the exploration framework in pdf. Thoughts and discussions welcome.

References:
Phobos: http://forum.nasaspaceflight.com/index.php?topic=18339.0
Mars EDL: http://forum.nasaspaceflight.com/index.php?topic=18387.0
Electric Propulsion: http://forum.nasaspaceflight.com/index.php?topic=18943.0
Large inflatables: http://forum.nasaspaceflight.com/index.php?topic=18759.0


Offline Idol Revolver

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Re: Phobos as a destination - a routemap
« Reply #1 on: 10/31/2009 11:11 am »
This would require a very big budget increase. And moon-first people would be very annoyed.

Offline alexterrell

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Re: Phobos as a destination - a routemap
« Reply #2 on: 10/31/2009 01:02 pm »
Though according to the Augustine Commission:

Quote
The plan of the Constellation Program for the exploration of the Moon envisions launching about 600 metric tons (mt) per year to low-Earth orbit, while exploration along the Flexible Path may require somewhat less launch mass each year. NASA scenarios for the exploration of Mars will have comparable annual requirements.
The Phobos routemap has slightly less mass in LEO requirements than 600 tons.

It also has no need for an Altair lander early on, though does need Exploration Ships, and SEP Tugs.

I'd have called myself a moon-first person till I looked at Phobos.
« Last Edit: 10/31/2009 01:03 pm by alexterrell »

Offline sandrot

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Re: Phobos as a destination - a routemap
« Reply #3 on: 10/31/2009 01:29 pm »
[...]
The Phobos routemap has slightly less mass in LEO requirements than 600 tons.
[...]

Arianespace launched about 42 tons over 10 months. Where's my heavy lift?  ;)
"Paper planes do fly much better than paper spacecrafts."

Offline meiza

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Re: Phobos as a destination - a routemap
« Reply #4 on: 10/31/2009 02:14 pm »
Tugs from LEO to L1 - which L1? EML1? SEL1? Sun-Mars L1? What's the delta vee from the "L1" to Phobos?
Why so high ISP?
Why Jupiter? Etc etc.

I find things are just stated, no reasoning behind them is given.
« Last Edit: 10/31/2009 02:16 pm by meiza »

Offline alexterrell

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Re: Phobos as a destination - a routemap
« Reply #5 on: 10/31/2009 03:13 pm »
Tugs from LEO to L1 - which L1? EML1? SEL1? Sun-Mars L1? What's the delta vee from the "L1" to Phobos?
Why so high ISP?
Why Jupiter? Etc etc.

I find things are just stated, no reasoning behind them is given.
Thanks for the feedback :) - if I wanted to give all the reasoning, the document would be a bit long. A lot of it's been thrashed out in forums here.

L1 is Earth - Moon L1, as stated. Sun Earth L1 might have slightly better delta-V advantages, but it's a lot further, which is an important consideration for crewed vehicles.

I've assume the Delta V from EML1 to Phobos is 1.7km/s for chemical propulsion and 8km/s or electric (or 15km/s from LEO).

The "high" Isp refers to solar electric propulsion. It's high because plenty of energy is available (because of the long timeframes).

Jupiter? Why not. It's as likely or unlikely as any other HLV to get built. Instead of about six J-246 per year you could go for about 24 Falcon 9H launches per year. Except for the inflatable habitats, most cargos are divisible. Jupiter 246 also has the possibility of large payload fairings, which NSC lacks.


Offline meiza

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Re: Phobos as a destination - a routemap
« Reply #6 on: 10/31/2009 04:59 pm »
Yes, your explanations make sense but could they be in the document? Everything does not have to be explained from the ground up but it doesn't give the reader anything if stuff just seems completely arbitrary.

When L1 is introduced it should be mentioned it's the Earth-Moon L1. Immediately, right in the same sentence, and probably before the whole L1 abbreviation is used, not several chapters later.

The delta vee from EML1 to Phobos should be mentioned to highlight the advantage.

High ISP could make sense, very low accelerations... But still it requires some investigation, if the delta vee is 15 km/s does it make sense to have 30 or 60 km/s exhaust velocity?

Jupiter, yes, as a notional option etc... just that imho it doesn't do justice to the architecture to specify one launcher.

Offline alexterrell

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Re: Phobos as a destination - a routemap
« Reply #7 on: 11/02/2009 08:46 pm »

High ISP could make sense, very low accelerations... But still it requires some investigation, if the delta vee is 15 km/s does it make sense to have 30 or 60 km/s exhaust velocity?

My assumption is, if you halve the Isp, from say 5000 to 2500, you can halve the mass of the power supply (10 tons to 5 tons) but double the mass of propellant (from 20 tons to 40 tons).

So, ideally, propellant mass should equal power supply mass (for a one shot mission), which would be at about 7,000 seconds. However, this may be higher than VASIMR can achieve. Also, there are some who see very large solar arrays as impossible.

(This assumes linear delta-V:exhaust V relationship, which is a bit of a simplification).

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