LEO-to-GEO Tug Part 1: Cheaper than a Delta-IV Heavy

Delta-IV Heavy

In response to recent blog posts about LEO tugs servicing Iridium’s satellite constellation, readers have been asking me about other uses for orbital tugs.

One tug use that keeps coming up in our discussions is a LEO to GEO transfer tug. Such a tug would pick up a payload in LEO and transfer the payload to GEO, drop the payload off in the correct orbit, and return to LEO for its next payload.

Although there are some intriguing propulsion technologies on the horizon that make the case for such a tug easier to close, could a transfer tug be developed today with today’ s propellants to serve the extreme ends of the GEO Satellite market (projected for the next decade to be 20-25 satellites per year)?  I focused my analysis on two GEO market segments:

1. Smallsats (550kg) and 
2. Mega ComSats (6,000-10,000kg)

So I did some analysis (yay, spreadsheets!).

With current propulsion, could a LEO to GEO transfer tug work for: 

• SmallSats? NO, a LEO to GEO transfer tug could not be operated for less than the cost and performance of existing EELV rides
• Mega ComSats? MAYBE: and the rest of this post discusses my analysis as to why an entrepreneur may find a market here.

Currently the largest GEO ComSat could theoretically have a mass of 6,276kg if launched on a Delta IV Heavy (correct me if I am missing a commercial rocket offering a larger BOL value for a GEO sat). I have heard of prices for this type of launcher ranging from $150-200M (maybe more). Since such a satellite in my example would push the boundaries of the capabilities of the Delta IV Heavy, I used the upper end price point of $200M to GEO.

I am assuming a commercial customer with a 6,276kg satellite could purchase a GEO ride on a Delta-IV Heavy for $200M. My analysis considered how to transport a 6,276kg satellite from the earth’s surface to GEO for less than $200M. 

The Falcon 9 has a LEO payload limit of 10,450kg.  My analysis assumes a Falcon 9 to launch the satellite to LEO and tug to take the satellite from LEO to GEO.  I considered two propellant options for the transfer tug:

1. LOX/Kerosene at 340 ISP
2. LOX/Hydrogen at 450 ISP

The table below shows the price comparison between the baselined Delta-IV and a Falcon 9/tug combo using both propellant options. 

The Falcon 9 & LOX/Hydrogen tug combo could deliver the satellite to GEO for only $142M (a cost savings of ~30%). The LOX/Kero tug at a lower ISP shows a cost savings of 6% (more if the launch costs end up being more than $200M). I am not sure 6% cost savings would overcome the risk of introducing a tug into the satellite-to-GEO equation, but 30% savings for the LOX/Hydrogen tug ($60M!!) seems pretty tempting.


Here are my Assumptions:

• Tug is launched on Falcon 9 with a dry mass of 3,000kg.
• Tug is co-manifested on a Falcon 9. Launch cost $20M.
• Tug development paid for under contract and not a part of this analysis.
• Tug manufacturing Costs: $50M.
• Tug refuels itself as needed in LEO from additional Falcon 9 launches (10,000 kg of prop for $50M: $5,000 per kg).
• Tug lasts five years with amortization factored into price.
• Tug breakeven price listed in this analysis.
• Two missions per year assumed (8% Market Share).
• Operating Cost per year: $10M.
• LEO to GEO: 4200 m/s of delta-v required.
• GEO to LEO (with aerobraking): 1500 m/s of delta-v required.
• Use aerobraking from GEO to LEO.
• Satellite launched to LEO on a Falcon 9.

Observations:

1. Since propellant cost drives the price for this venture, true price reductions come not from increasing demand but from:

• Decreasing propellant usage [could be solved through advances in engine technology (VASIMR)] or
• Paying less than $5,000 per KG for propellant [could be solved through extraterrestrial sources of propellant? Or SpaceX lowering their Falcon 9 prices due to added reusability in their first stage].

2. Once in GEO, could the tug make more money after dropping off its payload and prior to returning to LEO? Two thoughts:

• Who would pay for prox-ops work in GEO?
• What could the tug bring back from GEO to LEO (the delta-v to return to LEO from GEO is very low with aerobraking making return payloads comparatively cheap)? Who would pay to have a payload brought back?

3. Entrepreneurs reading this would want to calculate desired IRR to determine attractiveness of opportunity to investors. I have only considered a breakeven price.
4. The Delta-IV Heavy does not fly very often. This Falcon 9/Tug solution offers increased flight opportunities in addition to the cost savings already mentioned – frequent launch opps alone may make this venture valuable to customers.
5. Because SpaceX’s Falcon 9 becomes much more attractive for Mega ComSat operators when including a tug, SpaceX may be interested in being involved in a commercial tug venture.
6. There are going to be some elements of this analysis I get wrong. Assume I made mistakes. I welcome the corrections.

LOX/Kerosene Tug Details:

LOX/Hydrogen Tug Details:

Click here to play with the interactive spreadsheets.

In the next post in this series, I will walk through the math for a 10,000kg satellite to GEO (bigger than anything currently in GEO), and the numbers look even better – all from a Falcon 9 and a transfer tug!