mˈoːɹ kˈɑːmplɛks dɪzˈaɪnz kæn ɪnvˈɑːlv pˈæsɪŋ ðə wˈɔːɾɚ θɹuː pˈʌmps ænd hˈiːt ɛkstʃˈeɪndʒɚz ænd ɛmplˈɔɪɪŋ nˈuːklɪɹ ɹɪˈæktɚz ɔːɹ sˈoʊlɚ hˈiːɾɪŋ; ɪɾ ɪz ˈɛstᵻmˌeɪɾᵻd ðæt ðiːz kæn ɡˈɪv ɐ spəsˈɪfɪk ˈɪmpʌls ʌv ˌoʊvɚ wˈʌnhˈʌndɹɪd nˈaɪnti fˈaɪv ˈɛs ˌaɪˌɛspˈiː, wˌɪtʃ ɪz stˈɪl wˈɛl bᵻlˌoʊ ðə stˈændɚdz ʌv mˈoːɹ kˈɑːmplɛks dɪzˈaɪnz, fɔːɹ ɛɡzˈæmpəl ðə fˈoːɹhˈʌndɹɪd sˈɪksti fˈaɪv ˈɛs ʌvðə hˈaɪdɹədʒənˈɑːksɪdʒən vˈɪnsaɪ ˈɛndʒɪn.
More complex designs can involve passing the water through pumps and heat exchangers and employing nuclear reactors or solar heating; it is estimated that these can give a specific impulse of over 195 s Isp, which is still well below the standards of more complex designs, for example the 465 s of the hydrogen-oxygen Vinci engine.