# Quick Ship & Mission Designer

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#### keermalec

##### Guest
Hi, in order to move discussions towards more quantitative solutions, I have made a small web-based ship designer, using data and mass fractions mostly from Borowski's 2002 Mars Design Reference Mission.<br /><br />Choose delta-v, acceleration, payload mass and thruster type, and the designer calculates the approximate mass manifest for your ship.<br /><br />Try it out here <br /><br /><br />PS: LANTR drives are LOX-Augmented Nuclear Thermal Rocket drives. LANTR 1 means a 1/1 mass ratio between LOX and LH2 propellant; LANTR 3 means 3/1 etc. The higher the ratio, the higher the thrust-to-weight ratio of the drive, the lower its tank mass, but the lower also its ISP (see Borowski page 10) <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

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#### qso1

##### Guest
I've been wanting to see something like this for years. Do you plan to market/sell it? <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

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#### keermalec

##### Guest
Lol no its just there for people to use.<br /><br />I do need comments on some parameters I use though. Basing myself on Borowsky's report and the Apollo Lander I get:<br /><br />structure mass= 7.5% of total mass<br />fuel tank mass = 14% of LH2 fuel mass, 2.5% for LOX, etc...<br />rcs mass = 0.5% of total mass <br />avionics mass = 2% of total mass<br />rcs propellant mass = 1.5% of total mass<br />aerobrake mass = 15% of total mass<br />landing gear mass = 7% of total mass<br /><br />In particular, I am not sure of the structure and landing gear mass figures. For landing gear I base myself on the Apollo landers but the numbers are not quite clear. Also structure mass seems to vary tremendously from 4% for a one-time use rocket to 20% for the Apollo Command Module for example. Any pointers here would be appreciated.<br /><br />Please note the results of this script are indicative only. it was made to help take design decisions such as whether to use an aerobrake or not and to make users aware of the relative performances of different drives in a real mission scenario.<br /><br />The figures include a 15% mass contingency as in the Borowsky report. This means that a real optimised project could come down with better mass figures. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

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#### qso1

##### Guest
I'll have to get back to you on the figures but they look fairly close to me. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

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#### thereiwas

##### Guest
Use fprint to format the numbers better. You have too many digits.<br /><br />

K

#### keermalec

##### Guest
Thanks thereiwas, I used printf and it looks much better.<br /><br />I also verified the tank mass fraction figures and tweaked them a bit. I took out the hydrazine/electric drive as that implies an electricity source which can have a pretty big impact on the final mass figures. <br /><br />I also modified the mass fractions in order to come closer to the Borowsky designs:<br /><br />structure mass = 0.055<br />rcs mass = 0.005<br />avionics mass = 0.01<br />rcs propellantmass = 0.015<br />aerobrake mass = 0.15<br />landing gear mass = 0.07<br /><br />I will make a low-thrust/high ISP drive calculator for ion, plasma and other electric drives when i have some time. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

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#### j05h

##### Guest
Thanks Keermalac!!<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

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#### keermalec

##### Guest
Updated the code once more. It now conforms much more to Borowski's numbers, which I have spent some more time decifering:<br /><br />structure mass = 0.04<br />rcs mass = 0.005<br />avionics mass = 0.01<br />rcs propellant mass = 0.015<br />aerobrake mass = 0.15<br /><br />I completely took out landing gear as Borowski seems to think this does not add additional mass to the lander, replacing it with the option of adding or not RCS thrusters, as these are negligeable for landers/lifters.<br /><br />The figures obtained now look very close to Borowski's (page 19, 2011 Cargo lander Mission):<br /><br />Earth-Mars transfer vehicle:<br />-----------------------------------<br />Delta-v: 3.6 km/s<br />Acceleration: 0.2 Gs<br />Aerobrake: NO<br />RCS: YES<br />Drive type: LANTR 0 (isp 941 s)<br />Payload: 66.04 tons<br /><br />Structure: 5.54 tons <br />Tanks: 6.59 tons <br />Thrusters: 9.05 tons <br />RCS thrusters: 0.69 tons <br />Avionics/aux. power: 1.38 tons <br />Main thruster propellant: 47.05 tons <br />RCS propellant: 2.08 tons <br />Aerobrake shell: 0.00 tons <br />Payload: 66.04 tons <br />Total mass: 138.41 tons (Borowski: 137.14 tons)<br /><br /><br />Mars descent vehicle (includes parachute as payload):<br />--------------------------------------------------------------------<br />Delta-v: 0.632 km/s<br />Acceleration: 0.8 Gs<br />Aerobrake: YES<br />RCS: NO<br />Drive type: LCH4/LOX (isp 379 s)<br />Payload: 40.94 tons<br /><br />Structure: 2.61 tons <br />Tanks: 0.32 tons <br />Thrusters: 0.80 tons <br />RCS thrusters: 0.00 tons <br />Avionics/aux. power: 0.00 tons <br />Main thruster propellant: 10.72 tons <br />RCS propellant: 0.00 tons <br />Aerobrake shell: 9.77 tons <br />Payload: 40.94 tons <br />Total mass: 65.16 tons (Borowski: 66.04 tons)<br /><br /><br />Mars ascent vehicle:<br />--------------------------<br />Delta-v: 5.625 km/s<br />Acceleration: 0.8 Gs<br />Aerobrake: NO<br />RCS: NO<br />Drive type: LCH4/LOX (isp 379 s)<br />Payload: 4.8 tons<br /><br />Structure: 1.87 tons <br /> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

K

#### keermalec

##### Guest
Code has been updated finally after I transferred my data from my old to my new comp.<br /><br />Aerobrake shell mass is now a function of entry velocity and calculating mission delta-v budgets is more detailled.<br /> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

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#### a_lost_packet_

##### Guest
You know, this is pretty cool. Thanks!<br /><br />You could build a nice little informative website around that idea. IIRC, NASA did a page similar to that but much, much less esoteric. They had it on their kids outreach/educational section along with a neat little animation. You could build a spaceship, dedicate space for certain things, choose the engine type, etc..<br /><br />You should do something like that as well. Heck, I wouldn't doubt that some teachers would want to use that sort of thing as instructional aids for their students. <div class="Discussion_UserSignature"> <font size="1">I put on my robe and wizard hat...</font> </div>

K

#### keermalec

##### Guest
Thanks a_lost, I was actually thinking of something along those lines.<br /><br />I just corrected a bug in the code that was making arrival delta-v way too high. The deceleration delta-v at Mars after a Hohmann transfer into an elliptical parking orbit is only around 0.9 km/s, not 2 km/s which works only for a circular parking orbit.<br /><br />I added 3 small calculators that should allow each and everyone to work out delta-vs for all conceivable missions in the solar system.<br /><br />For example, to get from LEO to the Moon:<br /><br />1. Orbital Transfer Calculator<br /><br />Central body mass: 1 Earth masses <br />Body A orbit: 6570 km (low Earth orbit)<br />Body B orbit: 384000 km (Moon orbit)<br />Angle increment: 180Â° <br /><br />Result: 3.13 km/s to inject on a translunar orbit<br /> 0.83 km/s at the moon<br /> <br /> <br />2. Orbit to Escape Trajectory Calculator<br />(use this the wrong way round, ie to get from lunar escape velocity to lunar orbit)<br /><br />Planet mass: 0.0123 Earth masses (this is the moon's mass)<br />Planet radius: 1740 km (moon radius)<br />Orbit periapse: 50 km above surface <br />Orbit apoapse: 50 km above surface <br />Escape velocity at infinity: 0.83 km/s (from previous calculation)<br /><br />Result: net delta-v at low lunar orbit is 0.83 km/s (this is the necessary delta-v to be captured by the Moon into a 50km high orbit)<br /><br /><br />3. Lift to Orbit Calculator<br />(again we use this the wrong way round, to calculate landing delta-v)<br /><br />Planet mass: 0.0123 Eartt masses <br />Orbit periapse: 50 km above surface <br />Orbit apoapse: 50 km above surface <br />Atmospheric pressure: 0 bars <br />Planet radius: 1740 km <br />Planet day length: 28 days <br /><br />Result: delta-v to land on the Moon is 2.05 km/s <br /><br /><br />SUMMARY<br /><br />1. Trans-lunar injection at LEO (200 km altitude) is 3.13 km/s<br />2. Trip duration is 4.76 days<br />3. Low Lunar Orbit capture (50 km altitude) is 0.83 km/s<br />4. Lunar landi <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

K

#### keermalec

##### Guest
It is interesting to note that getting to and from Phobos costs less delta-v than getting to and from the Moon, thanks to aerocapture at Mars:<br /><br />Departure from LEO (200 km): 3.57 km/s <br />Course adjustments: 0.20 km/s <br />Aerobrake at Mars: 1.25 km/s <br />Post-aerobrake adjustment: 0.02 km/s <br />Circularise to Phobos orbit: 0.61 km/s<br />Land on or take-off from Phobos: 0.02 km/s<br /><br />Total propulsive delta-v: 4.42 km/s<br />Total aerobraked delta-v: 1.25 km/s<br /><br />If we consider the Delta IV Heavy launch vehicle, which can send 25.8 tons to LEO, the resulting lunar or phobos landing vehicles would have 3.98 and 6.01 payload mass respectively:<br /><br />Moon vehicle:<br />Propulsive Delta-v: 2.88 km/s <br />Aerobraked entry velocity: 0.00 km/s <br />Minimum acceleration: 0.34 Gs <br />Aerobrake shell: <br />RCS/avionics: checked <br />Drive isp: 465.00 seconds <br /><br />Structure: 0.39 tons <br />Tanks: 0.24 tons <br />Thrusters: 0.05 tons <br />RCS thrusters: 0.05 tons <br />Avionics/aux. power: 0.10 tons <br />Main thruster propellant: 4.81 tons <br />RCS propellant: 0.15 tons <br />Aerobrake shell: 0.00 tons <br />Payload: 3.98 tons <br />Total mass: 9.76 tons <br /> <br /><br /><br />Phobos vehicle:<br />Propulsive Delta-v: 0.65 km/s <br />Aerobraked entry velocity: 1.25 km/s <br />Minimum acceleration: 0.04 Gs <br />Aerobrake shell: checked <br />RCS/avionics: checked <br />Drive isp: 465.00 seconds <br /><br />Structure: 0.34 tons <br />Tanks: 0.06 tons <br />Thrusters: 0.01 tons <br />RCS thrusters: 0.04 tons <br />Avionics/aux. power: 0.08 tons <br />Main thruster propellant: 1.18 tons <br />RCS propellant: 0.13 tons <br />Aerobrake shell: 0.59 tons <br />Payload: 6.01 tons <br />Total mass: 8.44 tons <br /><br /><br />It is therefore cheaper to send a ton of equipement to Phobos than to the Moon...<br /><br /><br /> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

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#### keermalec

##### Guest
OK I've been working till 4 in the morning finalizing this.<br /><br />The Space Mission Calculator<br /><br />You can now calculate mission delta-vs to go from any planet or moon in the solar system to any other planet or moon. There are about 700 lines of code...<br /><br />Do tell me what you think, and if anyone can check some results, such as a transfer from Earth to Mars, all the better...<br /><br />Many thanx <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

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#### bpfeifer

##### Guest
Thank you.<br /><br />I don't have the skills and know-how to check your work, which is exacty why it's useful to me. Thank you. <div class="Discussion_UserSignature"> Brian J. Pfeifer http://sabletower.wordpress.com<br /> The Dogsoldier Codex http://www.lulu.com/sabletower<br /> </div>

K

#### keermalec

##### Guest
Added two new calculators: Faster than Hohmann transfers, and Low thrust vehicle design.<br /><br />Gravity losses are approximate estimates only. Ship design is based on current NASA designs and uses the Tsiolkovsky rocket equation to determine mass/delta-v relationships.<br /><br />Enjoy. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

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#### spacester

##### Guest
From your calculator page: <font color="yellow">Delta-v for continuous thrust transfers is the difference in orbital velocities between departure and arrival orbits.</font><br /><br />Um, I don't think so. Gravity losses are continuous and they add up to a large number compared to a transfer which is 100% energy efficient, which is Hohmann and only Hohmann.<br /><br />That paper I linked to a while back spelled it out. LOTS of coupling and gravity losses. The only reason continuous low-thrust works is the high Isp, allowing you to (eventually) deliver the MUCH higher dV needed as compared to near-instantaneous impulse trajectories.<br /><br />Any faster-then-Hohmann trajectory is higher dV than Hohmann, not just because of gravity losses, but primarily because the spaceship and planetary velocity vectors do not match direction. That's what Hohmann is all about: parallel vectors, lowest dV.<br /><br />With non-parallel vectors, some of the energy you expend thrusting is in a direction which does you no good <b>in terms of orbital energy.</b> This is what the concept of 'bound energy' is about. Some of the energy you spend getting to where you need to be (and at the right time to be there) does not get 'bound' to the orbit. Specifically, the radial component of any thrusting only affects potential energy, while tangential thrust contributes all kinetic energy. But only half of the PE is bound to the orbit (see the vis-viva equation). At least that's my understanding after years of beating my head on this stuff. <img src="/images/icons/laugh.gif" /><br /><br />With continuous thrust, you basically NEVER have parallel velocity vectors. Therefore there is no way they can be the loss-free value, which is what you get when you just look at the difference in orbital energies, as you indicate you are doing.<br /><br />Just to be clear, note that when I talk about dV, I'm talking about spaceship capability, not just a mathematical comparison of orbital speeds. Actual astrogation <div class="Discussion_UserSignature"> </div>

K

#### keermalec

##### Guest
Thanks spacester, you may ignore the continuous low thrust comment if you believe it is wrong. Opinions diverge on this but according to Vallado quoted by Stockermans the difference in orbital velocities is a good approximation of the total delta-v needed to change orbit using continuous low thrust. I only mention this on the first page because I do not want people to use the high thrust calculators (you will notice there are no low thrust calculators on my site) with low thrust vehicles where of course, gravity losses will be huge.<br /><br />Personnally, I am not sure that gravity losses should be accounted for in the case of continuous low thrust as thrust is always applied parallel to the gravity field. The vehicle naturally rises in the gravity field as its radial velocity, ie energy, goes up. We can discuss this, but I think a continuous low thrust thread would be appropriate as this is not the object of my online calculator. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

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#### spacester

##### Guest
Ah, I see. That's the link. Stockerman taught me a large chunk of what I know. But I'm no expert on continuous thrust numbers. <br /><br />Just time for a quick post this morning, more later. <div class="Discussion_UserSignature"> </div>

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#### keermalec

##### Guest
Hey spacester, this is actually quite funny: I fell upon our old "Continuous Low Thrust to Mars" thread and I realised you are the very one who gave me the link to Stockermann's page and told me to read thru it.<br /><br />You also corrected my then false assumptions on orbital transfers which ultimately lead to my writing of the online calculator.<br /><br />Since then I bought some books and worked thru the maths but your references and corrections have been an invaluable help to get there. ;-) <br /><br />PS: to anyone reading that thread: do not pay attention to the numbers given there. Everything is wrong. Use the Online Calculator instead. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

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#### spacester

##### Guest
<img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> </div>

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