The Falconator : dV spreadsheet for F9-style rockets

[RedKraken]

  Falconator spreadsheet  .... for armchair rocket scientists.

What happens to the payload if I mess with the Falcon's dry mass?

What does a pretend methalox falcon-7 send to GTO?

What if I shrink the first stage and lengthen the second to get a different delta-v split?

What about a full-figured methalox falcon-9 with larger diameter tanks?

What about a giant F9 with 3MN raptors?

This spreadsheet attempts to answer those questions using only the rocket equation.

Corrections and critiques welcome.

The F9FT data is widely available. The dry masses are speculation... but seem to match up with the SpaceX payload claims.

The methalox stuff is pure speculation.

Enjoy.

References :

http://spaceflight101.com/spacerockets/falcon-9-ft/ for prop masses and dry mass estimates of Falcon9FT

https://forum.nasaspaceflight.com/index.php?topic=41146.313 Reply 313 is Steve Pietrobon on prop densities

https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30473.0;attach=482367;sess=0 ModemEagle was modelling methane falcons in June 2012.

http://forum.nasaspaceflight.com/index.php?topic=34303.0 Hyperion5 hosts a NSF thread on converting the falcon 9 to methane in Nov 2012.

https://www.reddit.com/r/spacex/comments/4x6my1/fun_with_loxlch4_analyzing_a_falcon_9/ RulerofSlides contribution on reddit.

https://www.reddit.com/r/spacex/comments/64ew8x/falcon_9_a_systems_overview/ awesome community effort started by ap0r. There is so much Falcon 9 information in this one diagram. A methalox version of this would be frikkin gold.

 

Edited August 1, 2017 by RedKraken
ModemEagle reference from 06/2012

[sevenperforce]

This looks terrific!

While I'm sure I could dig into your spreadsheet and get this information, I'm curious and impatient, so I'll ask here:

• What TWR are you projecting for the Raptor and the 1000 kN dev Raptor?
• Are you factoring the lower density of methalox into your upper stage tankage ratio?
• What method are you using to determine gravity drag and aerodynamic drag, and is it fixed or TWR-dependent?
• What first-stage reuse penalty are you using? What second-stage reuse penalty are you using (or is there second-stage reuse)?

 

[RedKraken]

Hi Sev!

I have been following your threads with great interest.

 

1. EngineTWR :

I suspect it will come out around 200:1, based on the engine talk on NSF.

I use 500kg 1MN Mini-raptors and 1500kg 3MN Raptors in my RO adventures.

At the moment the spreadsheet has no explicit way to enter engine mass.

It is lumped into a stage dry mass for simplicity.

There are no dry mass estimates based on structure/materials/configurations for methalox......too far beyond what i wanted to do.

For the F9FT/Methfalc7 comparison, I wanted to start with the dry masses the same. But you can specify each explicitly.

I scaled up my dry masses for the larger diameter rockets (4.3m, 8.0m) using guestimates. Again, you can change this as required.

 

2. Bulk Methalox density :

I'm using 0.9kg/L for chilled methalox in the upper stage.

Same for the lower stage. No hybrids.

The F9FT tank volumes im using are 379000L lower and 99500L upper.

(calculated from chilled kerolox density of 1.08kg/L and 411000kg/107500kg prop loads)

Giving a methalox prop loading of 342360kg/89550kg.

Chilled methalox is 10500kg per meter of tank @ 3.66m diameter.

Take 2m (21000kg) of lower tank space and give to upper stage for final prop loads 321360kg/110550kg

Final LEO delta-v split is 5490/3700 m/s which is close to the F9FT at 5460/3720 m/s.

The delta-v splits for GTO expendable (8500/4000) and GTO reuse (7700/3900) match up too.

 

3. No flight profiles at all. Only delta-v for comparisons.

spaceX appear to like roughly 9200m/s (22800kg) for LEO, 11640m/s (8300kg) for expendable and 12465m/s (5500kg) for reuse.

Rocket TWR only calculated for sanity check.

 

4. Reuse and penalties :

Same as spaceX (first stage reuse only) :

F9FTs 5500kg GTO -> 12465 m/s as the delta-v reference point for reuse

 

Cheers!

 

Edited May 3, 2017 by RedKraken
raptor twr

[RedKraken]

Update V1.1

Error in length-change calcs.

Results : very small performance increase.

Falconator V1.1

[RedKraken]

Update V1.3

More mucking around with length adjustments.

Results : change in small kg/m.

[DDE]

I do happen to have a calculator for Falcon 9R first stage with Dragon 2 right on top of it, along with a dV calculator for suborbital hops. Anyone interested?

[Matuchkin]

"Methfalcon9", huh.

[Nothalogh]

10 hours ago, Matuchkin said:

"Methfalcon9", huh.

Chemically augmented 

[Matuchkin]

14 hours ago, Nothalogh said:

Chemically augmented 

Makes sense.

[Racescort666]

17 hours ago, Nothalogh said:

Chemically augmented 

Would that make Methfalcon7 a minor rocket?